Introduction 1

CHAPTER 1.

INTRODUCTION

1.1 Context and purpose

Horses were domesticated about 2,500 to 5,000-years ago (Clutton-Brock 1981).

Domesticated animals that return to a wild state independent from humans and are capable

of reproducing and sustaining a population are termed feral animals (McKnight 1976). In the

United States of America (USA), feral horses persist because they have (Berger 1986):

(1) flexible behavioural and physiological systems that enable them to adapt and reproduce

under a broad spectrum of ecological conditions; (2) occupy isolated, remote habitats; and

(3) are legally protected and regarded as a ‘national treasure’ that embodies ‘the historic and

pioneer spirit of the west’, under the Wild Free-Roaming Horses and Burro Act 1971 (Wagner

1983; Rutberg 2003). In Australia, feral horses inhabit a range of environments from deserts

to wetlands, and tend to be most abundant in the remote unfenced cattle production areas

of the northern states and in rugged mountainous country (Symanksi 1994; Csurhes et al.

2009). Unlike the USA, feral horses are not protected by legislation and in South Australia,

for example, are declared a pest species under the Natural Resources Management Act 2004

(Dawson et al. 2006). The majority of populations exist on public lands of conservation value

where government authorities such as the National Parks and Wildlife Service (NPWS) have

statutory obligations to reduce population numbers (English 2001b; Edwards et al. 2003).

However, many Australians and several public interest groups (e.g. Save the Brumbies,

Australian Brumby Alliance) either do not perceive feral horses as a pest species or regard

them as an iconic species of cultural and heritage significance that should be managed for

preservation in accordance with their status in the USA (Walter 2002; Ballard 2005; Finch and

Baxter 2007; Nimmo and Miller 2007; Nimmo et al. 2007).

Horse population control thus continues to be one of the most complicated problems

for wildlife management agencies worldwide due to multiple, often highly emotional, and

polarised attitudes of stakeholders (Wolfe 1980; Rikoon and Albee 1998; Rikoon 2006;

Hubert and Klein 2007; Kincaid 2008; Taggart 2008). These contrasting views were

epitomised by the public reaction to the aerial (helicopter) cull of 606 horses in Guy Fawkes

River National Park (GFRNP), New South Wales (NSW), in October 2000. Ballard (2005)

concluded that rarely has a wildlife management issue in Australia received such a sustained

level of public acrimony, domestic and international media coverage, and political

Introduction 2

involvement as the GFRNP cull. The direct ramifications of the cull were considerable and

included an official review of the GFRNP culling operation and horse management in all NSW

National Parks (English 2000, 2001b), a NSW Local Court case with 12 counts of animal

cruelty filed against the NPWS (NSW NPWS 2002), parliamentary allegations of corruption

(Fraser 2002) and a permanent ban on the aerial culling of horses in national parks in NSW

(AAP 2000), and the development of a management plan for the remaining horses in GFRNP

(English 2001a; NSW NPWS 2003). The critical points of contention in horse control are the

heritage value of the Australian ‘brumby’ versus the adverse effects of horses on the

environment and native wildlife. To date, no scientific studies on the ecological effects of

horses on Australian ecosystems have been published in peer-reviewed literature, despite

Australia reputedly having the largest population of feral horses world-wide at an estimated

300,000 to 600,000 individuals (Dobbie et al. 1993; Dawson et al. 2006). After the GFRNP

cull, the then NSW Minister for the Environment established a Heritage Working Party (HWP)

to determine the heritage value of the horses in GFRNP (Heritage Working Party 2002a). In

concordance with the official review (English 2001b), the Minister also directed the NPWS to

monitor the environmental impacts in GFRNP associated with horses (Debus 2002).

The purpose of this thesis is to independently assess the impact of feral horses on

select plant communities, soil properties and grazing native mammals (i.e. macropods) in

GFRNP. The results are discussed in relation to the knowledge of horse impacts elsewhere in

Australia and overseas and the implications for future management efforts.

1.2 Horse evolution and definitions

The mammalian family, Equidae (zebras, asses and horses) includes one genus

(Equus) with 18 extant native (wild) species or subspecies that are limited to Africa and Asia,

with a recent reintroduction in parts of Eurasia (Oakenfull et al. 2000). The one horse

species (Equus ferus) has three subspecies: the tarpan or Eurasian wild horse (Equus ferus

ferus), Przewalski’s horse or takhi (Equus ferus przewalskii), which is the only true extant (and

critically endangered) native horse species, and the domestic and feral horse (Equus ferus

caballus) (ICZN 2003). The other domesticated member of Equus is the domestic donkey or

feral ass (Equus africanus or E.asinus) (Oakenfull et al. 2000). The modern genus Equus first

appeared some 2 million years ago in North America from whence they spread to Asia,

Europe, Africa and South America (Kavar and Dovc 2008) to become one of the top four

grazing herbivores of the Pleistocene Mammoth Steppe (Guthrie 1990). Wild equids became

Introduction 3

extinct in North and South America some 8,000–12,000 years ago but survived and

diversified in Asia, Europe and Africa, for example, into numerous species and subspecies of

zebra in Africa inparticular (Martin 1970; Bennet and Hoffmann 1999). In western Europe,

rock engravings resembling the takhi have been dated at 11,000–22,000 years of age in Italy,

western France and northern Spain (Van Dierendonck and Wallis De Vries 1996). Wild horses

are thought to have existed in England until about 700 years ago, in Germany until

2000 years ago, and in Eastern Europe (e.g. Poland, Lithuania and Latvia) until the tarpan

became extinct sometime between 1814 and 1879 (Groves 1991; Levin et al. 2002; Kavar and

Dovc 2008). Some populations of specific breeds of feral horses have thus had an almost

continuous presence in Europe (e.g. Camargue horses in France, Konik polski horses in Latvia

and Poland) (Duncan 1992; Schwartz 2005). In North and South America, domestic horses

were progressively introduced from the early 1500s to 1700s (Darwin 1962; Berger 1986). In

Australia, they were introduced from 1788 onwards and in New Zealand in 1814, with the

first feral population in the Kaimanawa mountain region recorded in 1876 (MacDougall 2001;

Mincham 2008). Thus, evolutionary history may be generally described as long and

continuous in Europe, long but discontinuous in North and South America, and short in

Australasia. Differences in evolutionary history between Europe, both the Americas and

Australasia was described because those regions are where studies of the ecological impact

of feral horses have mostly been conducted (Section 1.4; Appendix 1). The inverse

relationship between the degree of exposure over evolutionary periods to large, generalist

herbivores and the responses of certain plant communities to grazing is an important

explanatory variable in some contemporary global models of grazing impacts (Mack and

Thompson 1982; Milchunas et al. 1988; Mack 1989; Milchunas and Lauenroth 1993). The

evolutionary history of feral horses thus provides a general background for evaluating the

international peer-reviewed literature on the environmental effects of feral horses. It also

provides clarification for terms used in this thesis. For example, coinciding with the heritage

perspective is an objection to the term ‘feral’, with preferences for ‘brumby’, ‘wild’, or

‘free-ranging horses’. Throughout this thesis the term feral horse will be used to describe

Australian populations as this has been independently assessed (English 2001b) as the

ecologically correct description of how horse populations originated and remain in the wild.

The same rationale applies to other populations arising from domestic introductions (i.e. the

Americas and New Zealand). In the interest of brevity, hereafter the term feral horse(s) is

also abbreviated to horse(s) with domestic populations referred to specifically in the context

Introduction 4

required, for example, stockhorse, recreational riding horse or the generic term of domestic

horse. The term ‘wild’ horse is akin to native and also has a specific ecological meaning,

namely ‘a species or race thought to have occurred in a geographical area before the

Neolithic’ (New Stone Age, circa 9500 B.C.; Manchester and Bullock 2000). This definition

only applies to the extant takhi subspecies of horse and the world’s species and subspecies of

‘wild’ equids, of which only the three subspecies of kiang (E. kiang) in Asia and five of the six

subspecies of plains zebra (E. burchelli) in Africa remain abundant and widespread (Duncan

1992).

1.3 Feral horse biology in relation to ecological impact potential

According to the so-called ‘tens rule’ for statistical regularities in biological invasions,

10% of introduced species become established in the wild, and 10% of those established

become a pest (Williamson and Fitter 1996a, b). Pest species are difficult to define (Perrins

et al. 1992) because species are pests for individualistic reasons (Williamson and Fitter

1996b). Across New Zealand and Australia, feral horses are considered a pest species and

have been assigned the same types of impacts as feral pigs (Sus scrofa) and feral goats (Capra

hircus), with the main impact being environmental degradation (Wilson et al. 1992; Cowan

and Tyndale-Biscoe 1997). Aspects of the biology and ecology of feral horses that predispose

the species to having an adverse affect on the environment are outlined in the following

sections. As horse impact studies in Australia are scarce, I also drew on the livestock (i.e.

cattle) grazing literature to develop experimental hypotheses about ungulate impacts

relevant to Australian ecosystems. Consideration was given to cattle (Bos taurus) to validate

the assumption that some environmental impacts associated with cattle in Australia may also

apply to horses with qualifications.

1.3.1 Home range, social organisation and mobility

Feral horse home ranges vary with environmental conditions, mainly the quantity and

quality of available forage biomass and physical barriers to expansion such as mountain

ranges (Rubenstein 1981; McCort 1984). Estimates of home range sizes are generally lower

for island populations (e.g. 90 ha on Sable Island) (Welsh 1975) and higher for semi-arid

populations (e.g. 30300 ha in the Wyoming Red Desert) (Miller 1983; Waring 1983b and

references therein). The estimates of 120 ha, 140 ha and 980 ha for three horses radio-

tracked in GFRNP (NSW NPWS 2006a) concur with those obtained in comparable temperate

Introduction 5

environments, such as New Zealand, and tend to be closer to the estimates for island

populations (59–1768 ha) (Linklater et al. 2000). The higher value for GFRNP was for a

dispersing colt, whereas mature horses in GFRNP, as in central Australia (Dobbie and Berman

1992), do not appear to move willingly from their home range, seasonal movements aside.

Feral horses are group-forming ungulates, with an average group (mob) size of 4.0–

7.7 horses commonly (Waring 1983a), but with multi-male breeding groups of over 30 horses

(herds) possible (Miller and Denniston 1979; Linklater and Cameron 2000). In GFRNP,

average group size has ranged from 4.4 ± 1.8 horses to 5.3 ± 2.6 horses (Vernes et al. 2009).

Feral horses are not typically geographically territorial (Ransom and Cade 2009) and mobs

may share watering, feeding and shelter sites with other mobs within overlapping home

ranges (Waring 1983b). However, stallions defend their mating rights with harem mares

(Rubenstein and Hack 2004) and can exhibit resource-orientated territoriality, particularly if

the resource is high quality or limited in extent (e.g. mineral resources) (Pellegrini 1971;

Bogliani et al. 1994; Ransom et al. 2007). Core areas are those smaller areas within a home

range that are used most frequently and probably include the homesites, refuges, and most

dependable food sources (Kaufmann 1962; Ewer 1968) and thus may be expected to include

sites where the direct consequences of horse activity (e.g. dung, dust wallows, tracks) are

clumped (Walters 1996). In the Kaimanawa horse population, the average (±1 S.E.) core area

(87 ± 8 ha, 50% utilisation) was much smaller than average home range size (539 ± 46 ha,

95% utilisation).

Seasonal movement has been reported in numerous horse populations (e.g. Miller

1980; Ganskopp and Vavra 1986; Crane et al. 1997a; Rheinhardt and Rheinhardt 2004).

However, unlike the abundant wild equids in Africa (e.g. plains zebra on the Serengeti Plain,

Tanzania where up to 280,000 zebras move 100–150 km, Grubb 1981), long-distance

seasonal migration en masse does not occur. Therefore even at lower regional densities,

localised feral horse impacts have the potential to be severe due to continual, concentrated

use by resident individuals within a mob or multiple mobs while systems supporting migrants

are apparently more resilient (Fryxell and Sinclair 1988). The rest periods associated with

migration can play an important part (in addition to fire and evolutionary history) in the long-

term persistence of plant–herbivore systems, particularly in areas with slow rates of

vegetation regeneration (Coughenour 1991; Holdo et al. 2007). Horses also have the

potential to affect a greater range of habitat types across a greater area than cattle due to

their superior mobility and agility. In more xeric habitats, horses travel further from water

Introduction 6

each day and in general, for example, up to 50 km in Central Australia (Pellegrini 1971; Green

and Green 1977; Berman 1991). While cattle walk as far as 25 km, they begin to lose

condition after 7 km (CSIRO 1981). To reduce energy expenditure or due to physical

limitations, cattle generally avoid grazing slopes over 6–11° and slope is an important and

consistent determinant of cattle distributions on mountain rangelands (Roath and Krueger

1982; Gillen et al. 1984; Bailey et al. 1996; Ganskopp et al. 2000). Conversely, in comparative

studies with cattle, it is typical for horses to rapidly traverse rugged or steep topography (up

to 45°) to gain access to relatively flat but elevated grazing terrain or high benches and ridge

tops to enhance the ‘viewshed’ (Pellegrini 1971; Miller 1980; Ganskopp and Vavra 1987).

Thus feral horses are more destructive of elevated, hill country than cattle (Hungerford

1980). Mobility also enables horses to form ‘reserve’ populations in areas inaccessible to

management and immigrate into areas after localised population control, or expand into new

areas if resources become limited due to density-dependent population growth.

1.3.2 High reproductive potential and density-dependent population growth

Early simulations and estimates of finite annual growth rates (λ) from aerial counts of

feral horses in western USA reported growth rates ranging from λ = 1.04 to λ >1.20 (Cook

1975; Conley 1979; NRC 1980; Wolfe 1980, 1986). However, all sources doubted if the high

reproduction and survival rates (>90%) required to produce growth rates around λ = 1.20

(i.e. increasing at 20% annually) are realistic, for reasons outlined in Garrott et al. (1991b), or

questioned the quality of the aerial counts (Frei et al. 1979; Symanski 1996). Similarly, initial

estimates of λ = 1.17–1.24 (Rogers 1991) for Kaimanawa horses in New Zealand were

thought to be exaggerated and revised to an average of λ = 1.10 and a biological maximum of

λ = 1.20 (Linklater et al. 2004), in agreement with Conley (1979). Subsequent studies revised

the age of first foaling from 3–5-years to 2–3-years, and allowed for foals in consecutive

years and annual survival rates of both adults and foals (to 1-year-of-age) have either

approached or exceeded 90% (e.g. Keiper and Houpt 1984), all of which contributed to

annual growth rates not less than λ = 1.15, with most estimates approaching or exceeding

λ = 1.20 for North American mainland and island feral horse populations (Eberhardt et al.

1982; Kirkpatrick and Turner 1986; Garrott and Taylor 1990; Garrott et al. 1991a; Garrott et

al. 1991b and references therein; Garrott et al. 1992; Kirkpatrick and Turner 2003). Even

higher finite annual growth rates have been reported for horses in the French Camargue

(yearly maximum, λ = 1.31, average λ = 1.27; Grange et al. 2009) and Argentina ( λ = 1.33;

Introduction 7

Scorolli and Cazorla 2010), supporting Duncan’s (1992) suggestion that λ values > 1.20 are

possible in feral horse populations. Such extreme rates are more likely at low densities or

over initial introduction periods as in the Camargue and at Lake Pape, Latvia, where the

number of horses doubled in the first 2 years after being released (Prieditis 2002).

Feral horse population growth appears to be density-dependent, possibly due to

social stress but mostly due to food limitation (Scorolli and Cazorla 2010), resulting in lower

growth rates (e.g. λ = 1.03–1.07; Goodloe et al. 2000). Thus, even if high-density populations

fall or ‘crash’, it would be after most of the available forage biomass has been removed, as

occurred with the Camargue and Lake Pape re-introductions, with potential consequences

for other wildlife and ecosystem processes (Duncan 1992; Prieditis 2002). By reacting to

changes in density, horse populations can also recover quickly from controlled or stochastic

reductions (e.g. severe winters, fire) by marked increases in foaling rates and reproduction at

an earlier age (e.g. Garrott and Taylor 1990).

In Australia, historical counts of horse numbers and population dynamics in the

Northern Territory have been debated (Symanksi 1994). Methods and personnel have been

more consistent in the Australian Alps National Park (AANP), where feral horse population

growth rates have shown recent evidence of density-dependent recovery aided by range

expansion (Walter 2002). After a dramatic population decline between 2001 and 2003,

coinciding with severe and extensive wildfires, the estimated average rate of increase was

21.7% per annum (λ = 1.21) for 2003–2009, which has been associated with the potential for

greater environmental impacts (Dawson 2009a; Booth and Low 2010). While empirical

evidence is lacking for GFRNP, based on the demography of captured horses, the rate of

increase per annum may be as high as 16% (NSW NPWS 2006b). In AANP and GFRNP, growth

rates may be inflated during temporary periods of abundant food supplies, lack of crowding

or range expansion in combination with no appreciable mortality due to disease or

predation. Such conditions have been documented for other large, long-lived mammals with

similar reproductive features as horses (e.g. bison, Bison bison) (Eberhardt 1985; Garrott et

al. 1991b and references therein).

1.3.3 Flexible feeding ecology

The perissodactyls (equids) originated at the same time as the other major group of

medium-sized grazing ungulates, the artiodactyls (bovids, e.g. cattle) (Schaeffer 1948). All

ungulates utilise symbiotic microorganisms to digest cellulose, either primarily in the rumen

Introduction 8

(foregut fermentation, bovids) or caecum (hindgut fermentation, equids). The highly

efficient ruminant digestion system has been cited as a reason for the spectacular

evolutionary success of bovids compared to equids which employ caecal fermentation (Moir

1968; Schmidt-Nielsen 1997). In the middle-fibre range (medium-quality grasses) (Janis

1976), the concentration of fibre is sufficiently low to allow high digestion co-efficients and

high intakes due to fast passage rates though the rumen (Campling and Lean 1983). This

‘nutrition model’ also predicts that caecal fermenters are more efficient digesters of low-

fibre and high-fibre plant tissues (Demment and Van Soest 1985), and that equids should be

able to extract more from grasses with very high fibre contents because food passes faster

through the hind-gut, which has no selective delaying mechanism (Menard et al. 2002). For

this reason, caecal fermenters are thought to and can eat relatively more than ruminants

(Alexander 1946; Van Soest et al. 1983), but not necessarily and Berman (1991) found no

evidence for feral horses consuming greater herbage biomass than cattle in central Australia.

Recent reviews and evidence from feeding trials with the Camargue horses in stalls and at

pasture (Duncan et al. 1990; Duncan 1992) confirm that feral horses have the potential to

live on coarser forage than bovids because they can ingest more dry forage per kilogram of

body weight per day (i.e. high intake rates). Their intake probably does not decline on coarse

forage because they extract nutrients faster from the lowest quality forage (Bell 1970, 1971;

Janis 1976). However, as horses ate 63% more forage than cattle when fed medium-quality

forage, horses acquire more digestible nutrients per day and likely achieve higher nutrient

extraction rates across a wide range of forage quality (Illius and Gordon 1992; Menard et al.

2002). Higher levels of forage intake have also been associated with longer daily grazing

times in feral horses compared to cattle (Fleurance et al. 2001; Vulink 2001): 50–73%

compared to 32–48% of their time, respectively (Lamoot et al. 2005 and references therein).

The greater invasion of exotic plants in natural grasslands in terms of richness and cover

under feral horse compared to cattle grazing in Argentina was attributed to the above

differences in digestive physiology and ecology, as well as the larger body size and mass of

feral horses making a larger impact on the structure of the vegetation and on the soil surface

(Alejandro et al. 2010). The area covered by feral horse dung in natural grasslands (2.5%)

was also greater than results obtained for cattle elsewhere (0.4–1.0%) (Loydi and Zalba 2009

and references therein).

On the basis of digestive system, metabolic requirements, body size, and comparative

diet studies in desert sagebrush steppe (Hanley and Hanley 1982; Ganskopp and Vavra 1986;

Introduction 9

McInnis and Vavra 1987; Crane et al. 1997a), feral horses are considered to be bulk grazers

and one of the least selective ungulates in western North America (Beever 2003). However,

in more heterogeneous and productive environments, horses feed selectively, switching

preferences seasonally to seek out the greenest food plants and foraging selectively amongst

and within different plant communities and habitats, sometimes producing a heterogeneous

mosaic in vegetation structure of tall and short swards (Duncan 1983; Ganskopp and Vavra

1986; Duncan 1992; Loucougaray et al. 2004). The flexible feeding ecology outlined above

has assisted feral horses to persist under a broad range of ecological conditions (Berger

1986). It follows that the range of environmental impacts due to horses is also broad with

variable outcomes as horses respond to their environment in a heterogeneous fashion

(Turner 1987; Nimmo and Miller 2007)

1.4 Feral horse ecological impact studies and densities

1.4.1 Impact on plant communities

General models of the effect of grazing on plant communities predict that grazing:

(1) increases species richness due to reduction of competitive dominants, especially at

intermediate grazing levels; (2) can stimulate primary production at low and moderate levels

while extreme levels reduce the photosynthetic capacity of vegetation; (3) results in

increases in less palatable or non-preferred species; and (4) facilitates the invasion of exotic

plant species (McNaughton 1979, 1985; Stohlgren et al. 1999; Milchunas 2006). All of these

effects have been documented in the international literature for feral horse grazing and are

summarised in Appendix 1.

1.4.1.1 Europe

Horses were re-introduced as ecological substitutes for wild horses (Bunzel-Drűke

2001) into wetlands in conservation areas in parts of the Camargue in France, and other

European countries (e.g. Lake Pepe, Latvia and Biebrza Marsh, Poland) in order to restore

and enhance plant and bird diversity (Heath et al. 2000; Bokdam et al. 2002; Borkowski

2002). The vegetation had moved towards dominance by a monoculture in the absence of

grazing (Tamisier and Grillas 1994; Schwartz 2005). In an artificial small-scale grazing

experiment in the Camargue wet grasslands, plant species diversity was maximised under

horse grazing and the structural heterogeneity of the vegetation increased (Loucougaray et

al. 2004) (Appendix 1). The authors argued that grazing by horses (and mixed grazing with

Introduction 10

cattle) was an optimal management regime for conservation purposes as the horse-induced

heterogeneity favours many species of waterfowl of international conservation importance,

and wigeon (Anas penelope), an important game species, prefers short swards created by

horses (Vulink et al. 2001).

During the initial 5 years after horses were released into the Camargue, densities

ranged from 0.042 horses/ha to 0.131 horses/ha and the impact on the vegetation was slight

over most of the 300 ha of range (Duncan 1992). The robust response of the vegetation was

not surprising given the long history of grazing, and average biomass increased concurrently

with the horse population due to high rainfall in the first few years, followed by notably drier

years (Vlassis 1978; Duncan 1992). The initial introduction at lower densities had the

desired effect of reducing the cover, height, biomass, frequency and density of the tall,

dominant perennial graminoid species. Once the competitive exclusion by the dominant

species was relaxed, the marshes and grasslands moved towards a more open structure with

a species-rich herb layer.

However, the Camargue herd was not managed and in less than 10 years, the density

peaked at 0.270 horses/ha and all horses were removed due to insufficient food resources.

The dominant, tall perennials were highly preferred by the horses, contributed most to

biomass and were intolerant of heavy, frequent defoliation (Duncan 1992). Some of the

dominant species were almost eliminated under the higher horse densities, and the primary

production of the marshes dropped to less than 20% (Duncan and D'Herbes 1982; Menard et

al. 2002). In the marshes, total species richness did not increase but the biomass of non-

preferred submerged annual plants, virtually absent from the ungrazed plots in exclosures

presumably due to competition with the dense tall reeds, increased under grazing (Duncan

and D'Herbes 1982). Total species richness also increased in the grasslands as the number of

annual grasses and forbs increased in frequency and abundance in grazed plots while

declining in ungrazed plots (Duncan 1992). As predicted by general grazing models, the only

perennial species that maintained themselves or increased under grazing were not important

food species for horses. Duncan (1992) concluded that continual high grazing pressure by an

unmanaged population of horses would in the long term lead to a shift to vegetation

communities with a very low capacity to sustain large mammals. Undesirable impacts of

over-grazing were also recorded at Lake Pepe with a harem group that had no ability to

expand its home range (Prieditis 2002). In the New Forests in the United Kingdom, feral

ponies have also had major impacts on vegetation structure and species composition,

Introduction 11

preventing natural regeneration of the herbaceous groundstorey and shrub and tree layer

over large areas of forest (Mountford and Peterken 2003).

1.4.1.2 The Americas and Australasia

Effects similar to the major impact of feral horse grazing in the Camargue have been

documented in wetland ecosystems on the North American Barrier Islands and in riparian

flush zones in New Zealand (Appendix 1). On the Barrier Islands, feral horses were not

restricted in their range movements, but their activities were concentrated in the salt

marshes (Eline and Keiper 1979; Turner 1987, 1988; Furbish and Albano 1994) (Appendix 1).

On island foredunes, the removal of perennial vegetation led to an increase in the area of

bare sand and a reduction in dune height and topography, contributing to the accelerated

erosion of sand dunes (Seliskar 2003; De Stoppelaire et al. 2004). In New Zealand, flush

zones have been highly modified by a history of feral horse grazing and are now dominated

by adventive grasses with the potential to threaten habitat for rare or regionally significant

plant species (Rogers 1991, 1994).

The impact of feral horses in semi-arid environments on the North American

mainland has been variable in comparison. At sites adjacent to springs, plots grazed by

horses recorded a reduction in vegetation height, cover and total species richness and an

increase in grazing-resistant forbs and exotic species, in comparison to ungrazed plots

(Beever and Brussard 2000a; Beever et al. 2008). Regional horse densities were relatively

low (<0.030 horses/ha; Berger 1986), yet sites closer to water have been shown to incur high

grazing pressure in grazing gradient studies (Landsberg et al. 2003; Hoshimo et al. 2009).

Berman (1991) also found that the environmental impacts of horses in central Australia, such

as the removal of herbaceous ground cover, diminished as distance from permanent water

increased (Appendix 1).

In exclosure studies not necesarily close to watering points, significant effects of

horse exclusion were found only for biomass and percent cover of one or two dominant

graminoid species preferred by horses (Fahnestock 1998; Fahnestock and Detling 1999a,

1999b). The authors suggested that horse densities or length of exclusion time were

sufficiently low to prevent major changes in grassland vegetation (Detling 1998). Changes in

cover and plant species composition were typically determined more by inter-annual

differences in rainfall (above average wet versus dry years) or by site variation than grazing

(Fahnestock 1998; Fahnestock and Detling 1999b) (Appendix 1). A modern history of

Introduction 12

continual grazing at relatively low regional densities (0.011–0.020 horses/ha, Appendix 1)

probably contributed to the ability of the dominant graminoids to withstand frequent

defoliation via morphological adaptations that led to compensatory growth (Fahnestock and

Detling 1999a, 2000).

1.4.2 Impact on soil surface properties, tracks and weed dispersal

Beever and Herrick (2006) found 3.0–15.4 times lower penetration resistance in

surface soils and 2.2–8.4 times greater abundance of ant mounds at horse-removed sites

compared to horse-occupied sites, with the range in differences explained by elevation.

Other studies have concentrated on feral horse tracks, which are typically linear pathways of

bare, compacted soil created by repeated trampling and prone to erosion (Jarman et al.

2003; Ostermann-Kelm et al. 2009). In Australian environments, track networks can be quite

extensive, ranging from 3.4–5.8 km of track per km2 in the Alps (Dyring 1990; Andreoni

1998). Plant species richness has been found to decline on tracks and the soil disturbance

caused by trampling and removal of vegetation can create conditions that aid in the dispersal

of exotic species, as does horse dung (Dyring 1990; Taylor 1995; Campbell and Gibson 2001).

In the Americas, while dung, assisted by gap creation and soil disturbance, may facilitate the

invasion of exotic species, dung piles may also provide a refuge from grazing for some grazing

sensitive species (Loydi and Zalba 2009; Alejandro et al. 2010). At intermediate levels of

disturbance native plant richness has also been found to be greater near tracks and dung

piles (Ostermann-Kelm et al. 2009).

1.4.3 Indirect impact on wildlife species and faunal communities

Across Europe, the effect of re-introducing horses on bird communities has been

variable: some species increased and others declined, depending on their ecological niche

and requirements for breeding and predator avoidance (Duncan and D'Herbes 1982; Duncan

1992; Bokdam et al. 2002). In South America, Zalba and Cozzani (2004) found higher avian

richness and diversity in areas under moderate or intermediate levels of grazing than areas in

which horses had been excluded. In areas of high intensity grazing, however, habitats were

less diverse and the rate of egg predation increased, leading to a reduction in the richness

and density of birds. On one of the North American Barrier Islands, bird richness increased

but the feral-horse-induced changes in vegetation structure altered bird communities in the

marshes and reduced the value of the marshes as nursery grounds for fishes and decapods

Introduction 13

(Levin et al. 2002) (Appendix 1). On the North American mainland, increased soil-surface

hardness affected small mammal assemblages, in particular fossorial species, with an

increase in those species insensitive to disturbance (Beever and Brussard 2004). Small reptile

diversity and abundance also declined. In terms of competition with native grazing

ungulates, feral horses may act as a competitor or facilitator (Berger 1985, 1986). Male

desert bighorn sheep (Ovis canadensis) forage greater distances from predator-avoidance

escape terrain when foraging with horses as opposed to conspecifics, and their foraging

efficiency increases as less time is spent on intraspecific aggression and social interactions

(Coates and Schemnitz 1994). Evidence of facilitation was not found in the same population

of horses and desert bighorn sheep when predator density was high, and as a result sheep

numbers declined. Rather, desert bighorn sheep changed their diet to minimise overlap with

horses (Kissell 1996 and pers. comm.). In Australia, several species of macropods, such as the

euro (Macropus robustus) and red kangaroo (Macropus rufus) have appeared to prosper in

conjunction with livestock grazing (Newsome 1975). The beneficial relationship between

kangaroos and cattle is based on cattle removing the dry, mature perennial pasture layer and

promoting nutritious new, green re-growth, which only kangaroos can graze based on

differences in tooth morphology (Frith 1970; Janis 1990). The foraging relationship between

horses and macropods is unknown, although exploitative (resource) competition has been

hypothesised (Olsen and Low 2006).

1.4.4 Summary

In conclusion, the preceding pages noted:

(1) the requirement for environmental impact studies in GFRNP and Australia

(2) the impact of feral horses and ungulate grazers on: (i) preferred perennial plants in

productive areas or where resources are limited; (ii) composition of plant

communities and plant richness indices; (iii) vegetation structure and ecosystem

productivity and biomass; (iv) condition of surface soils, such as loss of plant cover,

soil compaction, erosion and soil loss; (v) the ratio of native to exotic plant species as

horse dung can be an agent for dispersal of viable seeds and provide nutrients and

protection from climatic conditions and grazing herbivores; (vi) and native wildlife.

The aforementioned impacts have not been extensively examined in temperate–

subtropical ecosystems for feral horses in Australia and in addition to the requirement for

ecological impact studies in GFRNP, will be addressed in this thesis. Several reviews (Beever

Introduction 14

2003; Beever et al. 2003; Nimmo and Miller 2007; Abella 2008) highlighted knowledge gaps

in the understanding of the ecological effects of feral horses on native ecosystems which this

thesis also aims to address, such as:

(1) the uncertainty about the effect of feral horses at broader scales, for example: (i) at

the landscape scale where impact may vary according to factors such as topographic

position in the landscape (e.g. hillslope or spur), slope, aspect, elevation and habitat

type; (ii) on feed-back mechanisms between structural changes, such as a reduction

in ground cover and compaction of the soil surface, and aspects of landscape

function, such as soil surface stability, nutrient recycling, and water infiltration; and

(iii) indirect effects on medium sized herbivores (macropods) that occupy a similar

feeding niche as feral horses and the different effect horses may have from native

herbivores in regulating ecosystem processes, such as biomass accumulation, plant

species richness, and persistence of dominant tussocks via reproductive adaptations.

1.5 Thesis outline

The background to this thesis and purpose were briefly mentioned in the previous

section. In response to the limitations of previous feral horse impact studies, experiments

were conducted at a range of scales in several habitat types, utilising a broad set of response

variables, and the results were interpreted in terms of feedback loops between the direct

and indirect effects of feral horses. The objectives of this thesis as they relate to each

chapter are:

Chapter 2: to provide a context for experimental chapters by describing the environment

and climate of the general study area, GFRNP, and how levels of past and current feral

horse and cattle activity determined which parts of GFRNP were selected for a landscape-

scale comparison of horse and non-horse management zones or catchments

Chapter 3: to monitor dung counts of horses and macropods in conjunction with

reductions in feral horse numbers to test the relationship between horses and small-

scale habitat use and selection of foraging sites by macropods. In addition, the results of

dung counts showed the relative distribution of macropods in catchments with and

without horses

Chapter 4: to use exclosures on a high-elevation plateau to evaluate the response of the

groundstorey vegetation in open, grassy eucalypt woodlands associated with drainage

swales to horse grazing and trampling. The exclosure design enabled the effects of

Introduction 15

horses and native herbivores on the following variables to be compared: biomass, cover

and plant species richness indices, reproductive output of the dominant, perennial

tussock grass, and vegetation structure and composition

Chapter 5: to repeat the exclosure experiment on the most highly preferred landscape

unit, grassy riparian flats in a high-use gorge country in GFRNP

Chapter 6: to examine the effect of horses on the structural and functional integrity of

the dominant broad scale landscape units, hillslopes and spurs, in gorge country in

GFRNP heavily used by horses, with particular reference to horse tracks

Chapter 7: present a synthesis of the findings and conclusions, including implications for

management if horses were to remain or be eliminated from the Park, and further

research.

CHAPTER 2.

STUDY AREA

2.1 Introduction

The study area was in Guy Fawkes River National Park (GFRNP, or the Park) in north-

eastern New South Wales (NSW) (Figure 2.1a) and administered by the Dorrigo Plateau Area

Chapter 2. Study Area 16

office of the NSW National Parks and Wildlife Service (NPWS). The Park is on the eastern

edge of the New England Tablelands region of the Northern Tablelands Statistical Subdivision

of NSW, approximately 80 km and 40 km north-east of Armidale and Guyra and adjacent to

Ebor (Figure 2.1b). When established in 1972, the Park was 25 400 ha but now encompasses

100 600 ha, of which an area of 83000 ha was declared wilderness in 1994 under the

Wilderness Act, 1987 (NSW NPWS 2009b). The landscape is characterised by steep, narrow,

rocky gorges with narrow river flats along the bottom of the gorges. The Great Dividing

Range in eastern Australia was formed 80 to 90 million years ago and the ensuing erosion,

assisted by numerous river systems, marked the beginnings of the deeply incised and rugged

gorge country (McInherny and Schaeffer 2004b). Major river gorge systems include the Sara

River in the north (flowing east), the Aberfoyle River in the south (flows north-east), and the

Guy Fawkes River (GFR), which extends the length of the Park (flows north). The Aberfoyle

and Sara flow in to the Guy Fawkes River, which drains to the Boyd River in the northern tip

of the Park (Reid et al. 1996). Elevation varies from 200–300 m along the river flats to

1378 m at Chaelundi Mountain on the south-eastern boundary; most of the Park is remote

and has slopes between 10° and 30° (Reid et al. 1996). Over 40 vegetation communities have

been mapped containing 5% of Australia’s flora (Reid et al. 1996; Austeco 1999). The

vegetation of the higher elevation plateaus (1000 m) and slopes is mostly a mixture of

semi-mesic to dry sclerophyll forest communities with an open grassy understorey

(Henderson and Keith 2002). Climate follows a subtle gradient from subtropical at the

northern end of the Park (mean annual temperature >18°) to temperate on the tableland

plateaus and ridges above 800 m towards the southern and eastern borders (mean annual

temperature <15°) (Reid et al. 1996). Like temperature, rainfall varies with elevation from

800 mm in the river gorges to more than 1400 mm on elevated ridges and higher points on

the plateaus with a summer maximum and late winter–early spring minimum. At higher

elevations, frost appears at the beginning of March and is intermittent until November with

occasional snowfalls in winter (McInherny and Schaeffer 2004b).

Chapter 2. Study Area 17

Figure 2.1 a) Guy Fawkes River National Park (The Planning Area) within Australia (Google Maps) and b) regional locality map reproduced from NSW NPWS (2009b).

Chapter 2. Study Area 18

The Park is divided into 14 catchments based on the major river gorge systems and

their tributaries, also termed management zones (MZs; Table 2.1). Several catchments were

named after the tributaries that run through them, for example, Bobs Creek and Sara River.

To avoid confusion and repetition, and since this chapter describes the management history

of the Park, the term management zone will be used primarily and abbreviated to MZ when

referring to the catchment area, for example, Bobs Creek MZ and Sara River MZ. No

additional notation was used when referring to the tributary, for example, Bobs Creek and

Sara River. The term catchment will be used in all other chapters because of their ecological

context. The major rivers were identified previously; all other tributaries are creeks that flow

into one of those major rivers. Manipulative experiments involving exclosures were

conducted in two catchments, Bobs Creek and Paddys Land Plateau (Paddys Plateau

hereafter), and a landscape-scale survey conducted in Bobs Creek and three other

catchments, Pargo Creek, Kangaroo Creek and Pantons Creek. The objective of this chapter

was to describe the management history of each catchment with a focus on the length and

intensity of feral horse and cattle occupation. Cattle were a potential confounding factor

while horse densities provided the context for interpreting any ecological impacts of horses

detected. The selection of catchments for the landscape-scale survey in Chapter 6 is

summarised in Section 2.6.

Chapter 2. Study Area 19

Table 2.1 Areas of the Park that have been assigned a management zone (MZ) name and code by the NPWS Dorrigo Plateau Area office, accompanied by date acquired or gazetted, size and proportion of Park area of each MZ. Information provided by Brad Nesbitt or extracted from the relevant GIS shapefile and attribute table.

MZ code Management zone (MZ)

Date acquired Size (ha)

Area of the Park (%)

1 Pantons Creek–northern half 1995 760 3.2

Pantons Creek–southern half 2001 894 2 Upper Guy Fawkes River 1972 4857 9.4 3 Marengo 1972 2644 5.0 4 Aberfoyle River–western half 1999 1294

7.2 Aberfoyle River–eastern half 1972 2475

5 Combolo 1972 2524 4.8 6 Mid Guy Fawkes River 1972 4159 8.0 7 Kittys Creek 1972 3685 7.0 8 Paddys Land Plateau–western half 1997 3205

11.8 Paddys Land Plateau–north-eastern half 1999 3032 from Dingo Spur into Boban Tops/Hut

9 Bobs Creek–northern half 1972 1111 6.0

Bobs Creek–southern half 2000 2022 10 Pargo Creek 2000 2081 4.0 11 Sara River 1972 4826 9.3 12 Lower Guy Fawkes River 1972 4149 8.0 13 Glen Nevis Plateau 1997 4369 8.3 14 Kangaroo Creek 1972 4257 8.1

In Sections 2.1–2.3, ‘stock-horse’ implies ownership and refers to domestic horses

bred in captivity and released to run wild with the intent to recapture or muster the majority

of these for the lucrative remount export trade (1840s to 1940s). ‘Brumby’ refers mostly to

remnant populations of stock-horses after the 1940s when the remount trade had dried up

and large numbers of stock-horses were no longer turned loose with the purpose of breeding

up populations. Breeding between brumbies and stock-horses occurred but was not

targeted and generally occurred as a result of lack of fencing or escaped horses. ‘Feral horse’

or horse refers to the period after 1972 and the gazettal of the Park.

Several maps are presented in the following sections, and were created in a

Geographical Information System (GIS), ArcGIS v 9.1 (ESRI 2005). The Department of

Environment, Climate Change and Water (DECCW) GIS support officers, Lyn McRae and Annie

Blaxland, supplied numerous geographical and environmental data layers in addition to the

Global Positioning System (GPS) co-ordinates (text file format) for horse and cattle sightings.

For vector features (points, lines and polygons) (e.g. MZ polygon outlines, river polylines)

data sources were ESRI Shapefiles. Raster-based datasets were mostly ERSI Grid format (e.g.

Chapter 2. Study Area 20

digital elevation models, slope, rainfall) with a resolution of 1 ha (100 × 100-m grid cells).

The exception was topographic map layers, which were MrSID format (Multi-resolution

Seamless Image Database), a powerful image compressor, viewer and file format for massive

raster images. Data layers were accompanied by dBase tables (attribute tables) that

contained additional descriptive information (e.g. number of feral horses in a mob

corresponding to a single GPS point) used to create summary tables. Additional information

in hard copy (e.g. cattle infringement notices, letters of complaint) or verbal clarification was

provided by the Senior Ranger-in-Charge of GFRNP, Tony Prior, and the Pest Species

Management Officer, Brad Nesbitt, Dorrigo Plateau Area, NSW NPWS. Several long-term

resident graziers with property adjacent to the MZs of interest, and those descendents of the

early settlement families (e.g. Brian Fahey) were also consulted, as were horsemen

(e.g. Graham Baldwin, David O’Brien) involved with the horse musters as part of control in

the 1990s.

2.2 White settlement and early grazing history

Until the Park was gazetted in 1972, the area was inhabited and managed by graziers

for sheep and cattle grazing (Table 2.2, Figure 2.3). The first cattle station ‘run’ on the

Dorrigo Plateau was Guy Fawkes Station (GFS) established in the late 1830s by Major Parke;

it remains in operation today (Heritage Working Party 2002a). All original runs and station

properties including GFS have since been sub-divided. GFS increased in the 1880s and would

have included at least the southern tip of Pantons Creek MZ (Table 2.2) (Waugh 1971).

Kangaroo Creek MZ is located to the east and runs parallel to Pantons Creek MZ with pastoral

subdivisions corresponding to Dyamberin Station separating the two MZs. The Kangaroo

Hills Run was established in 1842 and in 1908 was divided into Wongwibinda (4900 ha) and

Dyamberin (6100 ha) Stations (Rampbeck Run) (MacDougall 2001). The first station

protruded into the southern tip of Kangaroo Creek MZ and the second encompassed the

eastern section of Kangaroo Creek and the western section of Pantons Creek MZs

(Figure 2.3). Sheep were grazed early on, for example, at stocking densities of

0.390 sheep/ha in 1844 at Kangaroo Hills (Table 2.2), with cattle now prominent. Parts of

Pantons Creek and Kangaroo Creek MZs were thus grazed to variable extents by sheep and

cattle for up to 161 years and 130 years respectively, as Pantons Creek was acquired for the

Park from 1995–2001 and Kangaroo Creek in June 1972.

Chapter 2. Study Area 21

At the same time as GFS was established, the Aberfoil Run was set up, and was

almost four times the size of GFS with stock numbers doubling from 1840 to 1844 (Table 2.2)

(McInherny and Schaeffer 2004b). Aberfoil was the original spelling for the name of this run,

and has been used in this thesis as it appeared in historical sources (e.g. published lease

details). The present day spelling of Aberfoyle was well established from about 1885

(McInherny and Schaeffer 2004a). From 1877 to 1883, at least fifty-three leases were taken

out on Aberfoil by early ‘free selectors’ (McInherny and Schaeffer 2004b). The Aberfoil Run

largely corresponded to the eastern portion of the Aberfoyle River and northern section of

Kangaroo Creek MZs, with a grazing history similar in length and intensity as Pantons and

Kangaroo Creek MZs (Table 2.2, Figure 2.2).

North-east of the Aberfoil Run and forming the northern boundary with the

Rampsbeck Run and Kangaroo Hills Run was an area settled in the 1880s and referred to as

Paddys Land (NSW NPWS 2009b) (Figure 2.2). The Newby family ran up to several thousand

head of cattle on Paddys Land in those early years (Fahey 1976). The station incorporated

the present day Paddys Plateau MZ and extended to the north and the east to include the

river flats on the western bank of the GFR into Kittys Creek MZ adjacent to Bobs Creek MZ.

Map of pastoral holdings up until the late 1990s indicated that the gorge sections of Bobs

and Pargo Creek MZs were never allocated to pastoral holdings (Heritage Working Party

2002a). This suggests that they were considered unsuitable for grazing due to the

topography and hence had a history of relatively minor cattle grazing (Heritage Working

Party 2002a). Stock-horses (and later brumbies and feral horses) from the neighbouring

Mt Mitchell (Henry River) and Paddys Land Run may have traversed that country, however,

as horses utilise a wide range of slopes, whereas cattle have a strong preference for flat or

gently undulating ground (Ganskopp and Vavra 1987; Chapters 1 and 6). Conversely, Paddys

Plateau MZ is flat relative to the greater area of the Park and appeared to be attractive to

early settlers given the number of dwellings it contained. Tallagandra Hut was occupied by

graziers until it was acquired by NPWS and is presently used as a field station and equipment

depot. Two Mile Hut, Braziers Hut, Wonga Hut and Boban Hut are either ruins or have

disappeared (Figure 2.2). Adjoining Paddys Land to the west was Wards Mistake, established

earlier in 1842 and may have included parts of Paddys Land in the beginning (Figure 2.2). The

large numbers of stock for the small areas (e.g. 800 ha) in the 1950s and 1970s (Table 2.2)

corresponded to the introduction of superphosphate fertiliser and sown pastures, as Wards

Mistake did not include the gorge country and had been extensively cleared and fenced.

Chapter 2. Study Area 22

Travelling Stock Routes (TSR’s), strips of public land set aside for the droving of stock,

were and are, still present in the Park. The major TSR follows the GFR in traversing the Park

in mostly a north–south orientation and is part of the Bicentennial National Track (BNT)

(Heritage Working Party 2002a). It was gazetted between 1880 (most northerly section) and

1900 (most southerly section), and the later date included a 6-km extension along

Macdonald’s Ridge from Combolo Hut on the banks of the GFR to Marengo Station (Boyd

1991). In 1922, the Combolo TSR was connected to the southern junction of the Sara River

and GFR by a second TSR. A third TSR joins it from Paddys Land in the west of the Park.

These routes are still used to move cattle illegally into the valley of the GFR from Newton

Boyd in the north, then along the GFR and up Macdonald’s Ridge into the only substantial

area of gently undulating land in the area known as the Fattening Paddock via Marengo flats

(Boyd 1991; Reid et al. 1996).

Chapter 2. Study Area 23

Figure 2.2 Location of the early settlement runs and stations relative to each other (McInherny and Schaeffer 2004b). Reproduced with the permission of the Guyra and District Historical Society. WAWM, Wongwibinda, Aberfoyle and Wards Mistake.

Chap

ter

2. S

tudy

Are

a 2

4

Tabl

e 2.

2 A

sel

ectio

n of

the

maj

or s

tatio

ns a

nd r

uns

that

wer

e ei

ther

adj

acen

t to

or

beca

me

part

of

the

Park

in t

he e

arly

whi

te s

ettle

men

t er

a.

Size

and

sto

ck d

etai

ls f

or t

he m

id-w

est

and

sout

h-w

est

regi

ons

wer

e ob

tain

ed f

rom

McI

nher

ny a

nd S

chae

ffer

(20

04b)

and

for

GFS

fro

m F

ahey

(1

976)

. Th

e br

ief d

escr

iptio

n of

the

rem

aini

ng r

uns

and

stat

ions

was

obt

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d fr

om M

acD

ouga

ll (2

001)

. G

FR: G

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ver.

Run

or S

tati

on

Year

se

ttle

d Lo

cati

on

Size

(ha)

St

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deta

ils

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king

de

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y

Sout

h-ea

st r

egio

n

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Faw

kes

Stat

ion

(GFS

) la

te 1

830s

Pa

nton

s Cr

eek

MZ

10 3

60

1,30

0 ca

ttle

0.

125

catt

le/h

a la

te 1

890s

16

190

Co

ntra

cted

to b

reed

hor

ses

for

Indi

an A

rmy

Litt

le G

uy F

awke

s St

atio

n la

te 1

830s

O

n th

e si

te o

f Ebo

r to

wns

hip

Cont

ract

ed to

bre

ed h

orse

s fo

r In

dian

Arm

y H

erna

ni S

tatio

n 18

40s

Adj

acen

t to

Mar

engo

and

Pan

tons

Cre

ek M

Zs

Catt

le a

nd h

orse

s Ba

ld H

ills

1850

s A

djac

ent t

o Ka

ngar

oo C

reek

MZ

Shee

p M

id-e

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tion

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y 18

50s

Mar

engo

MZ

and

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lund

i Sta

te F

ores

t Ca

ttle

and

hor

ses

Com

bolo

Sta

tion

1880

–188

4 Co

mbo

lo a

rea

MZ

Catt

le a

nd h

orse

s Ko

tupn

a Pr

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ty

1930

s A

djac

ent t

o M

id G

uy F

awke

s Ri

ver

MZ

Turn

ball

fam

ily b

red

hors

es fo

r In

dian

Arm

y N

orth

-eas

t re

gion

Br

oadm

eado

ws

Stat

ion

1849

Ki

ttys

Cre

ek M

Z, L

ower

and

Mid

GFR

MZs

Ca

ttle

and

larg

e nu

mbe

r of

hor

ses

Nor

th-w

est

regi

on

Mt M

itche

ll Ru

n 18

85

Adj

acen

t to

Parg

o Cr

eek

and

Sara

Riv

er M

Zs

Catt

le a

nd h

orse

s

Mid

-wes

t re

gion

War

ds M

ista

ke S

tatio

n 18

42

Adj

acen

t to

Padd

ys P

late

au M

Z an

d 23

070

2,

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catt

le

0.08

7 ca

ttle

/ha

and

Run

the

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rfoi

l Run

12

950

In

188

3: 3

,000

cat

tle, 3

0 ho

rses

, 50

shee

p 0.

232

catt

le/h

a 81

0 In

195

0s: 1

2,00

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810

In 1

970s

: 2,5

00 c

attle

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ddys

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d Ru

n 18

83

Padd

ys P

late

au M

Z U

p to

200

0 he

ad o

f cat

tle

Chap

ter

2. S

tudy

Are

a 2

5

Tabl

e 2.

2 c

onti

nued

. G

FS: G

uy F

awke

s St

atio

n.

Run

or S

tati

on

Year

se

ttle

d Lo

cati

on

Size

(h

a)

Stoc

k de

tails

St

ocki

ng d

ensi

ty

Sout

h-w

est

regi

on

The

Kang

aroo

Hill

s Ru

n 18

42

Kang

aroo

Cre

ek a

nd P

anto

ns C

reek

MZs

14

510

In

184

4: 6

60 c

attle

, 6 h

orse

s, 5

,600

she

ep

0.38

6 sh

eep/

ha

(sub

-div

ided

from

GFS

) In

185

5: 1

3,80

0 sh

eep

Won

gwib

inda

Sta

tion

1908

Su

b-di

vide

d fr

om K

anga

roo

Hill

s

4860

Ca

rryi

ng c

apac

ity o

f 0.5

0 sh

eep/

ha o

r 0.

11 c

attle

/ha

The

Ram

psbe

ck R

un

1867

In

bet

wee

n Ka

ngar

oo H

ills

and

Abe

rfoi

l Run

s 57

00

Carr

ying

cap

acity

of 0

.14

catt

le/h

a

The

Alfr

eda

Run

1865

A

djac

ent t

o Ka

ngar

oo H

ills

and

Ebor

65

0 20

0 ca

ttle

0.

301

catt

le/h

a

12 1

40

In 1

885:

28

catt

le, 6

hor

ses,

3,5

50 s

heep

0.

292

shee

p/ha

Abe

rfoi

l Run

18

39

Exte

nded

into

Abe

rfoy

le R

iver

MZ

and

38 0

80

In 1

840:

450

cat

tle, 3

hor

ses,

6,1

27 s

heep

0.

161

shee

p/ha

Kang

aroo

Cre

ek M

Z, a

djac

ent

to

In 1

844:

1,0

30 c

attle

, 29

hors

es, 1

0,92

6 sh

eep

0.28

7 sh

eep/

ha

Padd

ys P

late

au M

Z 45

130

In

187

6: 8

,000

cat

tle

0.17

7 ca

ttle

/ha

Chapter 2. Study Area 26

Figure 2.3 Location of the early pastoral settlement stations and runs in relation to present day management zones (MZs). TSR: Travelling Stock Route, GFS: Guy Fawkes Station, LGFR: Little Guy Fawkes Station. The number bolded in black in the centre of each MZs outline corresponds to the MZ Code in Table 2.1. 1: Pantons Creek, 2: Upper GFR, 3: Marengo, 4: Aberfoyle River, 5: Combolo, 6: Mid GFR, 7: Kittys Creek, 8: Paddys Plateau, 9: Bobs Creek, 10: Pargo Creek, 11: Sara River, 12: Lower GFR, 13: Glen Nevis Plateau, 14: Kangaroo Creek.

Chapter 2. Study Area 27

2.3 Feral horse history prior to Park gazettal

The MZs in the central-northern section of the Park had a similar history of

settlement and grazing as those in Section 2.2 (MacDougall 2001). The main difference was

that the Gulf Country, a term used to describe the dissected gorge country created by the

rivers and creeks in the region including the Guy Fawkes, Aberfoyle, Sara, Oban, and Henry

Rivers and the Bobs, Pargo, and Kittys Creeks (Figure 2.4) was not continually used by cattle

and sheep graziers (Heritage Working Party 2002a). Rather, the area was utilised over winter

because the gorges were always greener with higher quality feed (Fahey 1976). However,

the Gulf Country and the stations and runs in the central-north were associated more with

brumbies than the south in the mid 1900s (Table 2.3).

Written accounts of stock-horses did not appear until after 1920, but as early as

1871, a reward was offered for the capture of people responsible for the shooting of stock-

horses by William Coventry of Aberfoil in the Armidale Express (McInherny and Schaeffer

2004b). Stock-horses were in residence at GFS and Little Guy Fawkes Station (LGFS) from the

beginning, and an extensive herd was soon bred up and, without fencing, were free to roam

over thousands of acres (Fahey 1976). The early squatters largely followed Major Parke’s

example at GFS (e.g. Dyamberin Station, Bostobrick Station; Table 2.3). Up until the 1940s,

horse breeding for the overseas remount trade was a lucrative business, with the British

Army in India a major client (Fahey 1976; MacDougall 2001). Horses were bred from former

stock mares and turned out to run free in their hundreds (Heritage Working Party 2002a).

Mobs were run in or mustered on horse-back and depending on their quality and suitability,

many or just a few, were broken and sold in large consignments (e.g. 250 stock-horses from

Aboomala Station in the 1930s, Table 2.3). This tradition of mustering large mobs was

romanticised in Banjo Patternson’s The Man from Snowy River. The following also occurred

and became the common practice after the remount trade was no longer economic. Mobs

were mustered into make-shift yards (e.g. seven brumbies at Peaks Creek, 1933; Table 2.3)

and the best of the young brumbies were kept for local domestic stock horses, and the rest

shot to keep numbers down and reduce competition with cattle (Heritage Working Party

2002b). Rather than mustering mobs into yards, one or two were targeted for stock and

station work and ‘roped’, with injured or poor quality animals shot in the process.

Colloquially termed ‘brumby running’, this practice peaked during 1939–1945 when training

camps for the 12th Light Horse Brigade in the New England District required each solider to

provide his own horse and continued up until areas were gazetted as Park (Heritage Working

Chapter 2. Study Area 28

Party 2002a). Oral histories suggest that brumby numbers were always controlled prior to

World War II and started to build up in numbers after 1965 due to the lack of experienced

stockman and economic markets, boosted the technologies (e.g. sown and fertilised

pastures) that accompanied generational change, which made the ‘working horse’ redundant

(Heritage Working Party 2002b).

Chap

ter

2. S

tudy

Are

a 2

9

Tabl

e 2.

3 F

irst-

hand

acc

ount

s an

d or

al h

isto

ries

of

brum

by s

ight

ings

fro

m t

he 1

920s

to

whe

n ar

eas

first

bec

ame

Park

. Lo

catio

ns c

orre

spon

d to

‘k

ey lo

catio

ns’ i

n Fi

gure

2.4

. Pa

ge n

o. c

orre

spon

ds to

whe

re in

form

atio

n w

as o

btai

ned

in H

erita

ge W

orki

ng P

arty

(200

2b) a

nd M

acD

ouga

ll (2

001)

. Th

e in

form

atio

n is

sum

mar

ised

pic

tori

ally

in F

igur

e 2.

4 us

ing

a co

lour

cod

ed s

yste

m to

rep

rese

nt a

ppro

xim

ate

hist

orie

s an

d br

umby

num

bers

.

Loca

tion

Ye

ar

Obs

erva

tion

/com

men

t So

urce

Pa

ge

no.

Nor

ther

n re

gion

Day

s W

ater

nea

r Sa

ra R

iver

the

n so

uth

to

mid

193

0s

Form

er s

tock

mar

es tu

rned

out

to r

un fr

ee a

nd

Gen

evie

ve

New

bury

36

A

berf

oyle

Riv

er–M

itch

ell R

un w

est o

f Par

k be

com

e br

umbi

es

Corn

er C

amp,

upp

er (w

est)

Sar

a Ri

ver

nort

h

1940

s Br

umby

run

ning

occ

ured

, app

roxi

mat

ely

50 b

rum

bies

Er

nie

Mas

key

22

to H

enry

Riv

er

Broa

dmea

dow

s St

atio

n an

d ru

n 19

00–1

960s

Po

pula

tion

kept

und

er c

ontr

ol b

y pe

riod

ic m

uste

rs a

nd

Tiny

Hum

e co

ntra

ct s

hoot

ing

to r

educ

e co

mpe

titio

n w

ith c

attle

M

id n

orth

-eas

t re

gion

Co

mbo

lo F

lat

19

28

Brum

bies

sig

hted

and

sto

ck h

orse

s ra

n of

f with

a

Joe

Mee

han

24

mob

aft

er g

ate

left

ope

n Ki

ttys

Cre

ek ju

nctio

n w

ith G

FR

1930

s Br

umbi

es tr

appe

d an

d he

ld in

Litt

le P

lain

s Ya

rd

Dou

g M

eyer

36

M

aren

go S

tatio

n, s

tret

ch o

f GFR

bet

wee

n

1931

–32

Seve

ral b

rum

by m

uste

rs b

y fo

ur d

iffer

ent

stoc

kman

, tow

ards

N

oel M

acD

ouga

ll 23

Pe

ak C

reek

and

Litt

le P

lain

are

a en

d of

193

2 tr

ap y

ard

setu

p an

d br

ough

t gre

ater

suc

cess

Pe

ak C

reek

19

33

7 Br

umbi

es c

aptu

red

in tr

ap y

ard—

thou

ght t

o be

the

N

oel M

acD

ouga

ll 23

la

st o

f the

Bro

wn

fam

ily b

rum

bies

Ki

ttys

Cre

ek

1933

Re

calle

d no

bru

mbi

es a

t tha

t tim

e N

oel M

acD

ouga

ll 23

G

FR fl

ats

from

Mid

Guy

Faw

kes

Rive

r M

Z 19

35–3

6 Re

calle

d fe

w b

rum

bies

at t

hat t

ime

Jam

es H

icke

y 24

to

Mar

engo

MZ

Flet

cher

Bra

zier

19

45–4

6 5–

6 H

orse

s si

ghte

d al

ong

the

GFR

bet

wee

n Bo

yd R

iver

N

oel M

acD

ouga

ll 35

an

d Ki

ttys

Cre

ek

Com

bolo

and

Hou

sew

ater

Cre

ek a

rea

Late

194

0s

Reca

lled

no b

rum

bies

at t

hat t

ime

Noe

l Mac

Dou

gall

23

Litt

le P

lain

are

a, ju

nctio

n of

Lon

g G

ap C

reek

19

45–4

6 17

Bru

mbi

es s

ight

ed

Noe

l Mac

Dou

gall

23

Chap

ter

2. S

tudy

Are

a 3

0

Tabl

e 2.

3 co

ntin

ued.

Loca

tion

Ye

ar

Obs

erva

tion

/com

men

t So

urce

Pa

ge n

o.

Mid

nor

th-e

ast

regi

on c

onti

nued

Ki

ttys

Cre

ek a

nd C

ombo

lo a

rea

1970

A

roun

d 50

bru

mbi

es s

ight

ed, s

ugge

sted

that

bru

mbi

es

Erni

e M

aske

y 22

fr

om H

enry

Riv

er/C

orne

r Ca

mp

had

and

wer

e m

ovin

g do

wn

on

to th

e Sa

ra R

iver

and

late

r in

to K

ittys

Cre

ek/C

ombo

lo

Hou

sew

ater

Cre

ek a

rea

1970

s A

few

bru

mbi

es s

ight

ed

Terr

y Br

azie

r 24

W

ongw

ibin

da to

Litt

le P

lain

on

the

GFR

19

85

Whi

lst r

idin

g co

unte

d 26

8 br

umbi

es, m

ostly

from

D

oug

Ferr

is

25

GFR

–Pan

tons

Cre

ek Ju

nctio

n no

rth

to L

ittle

Pla

in a

rea

Litt

le P

lain

, 3 k

m u

pstr

eam

from

19

93

Erni

e M

aske

y le

d br

umby

mus

ter

and

in 1

0 ru

ns

Erni

e M

aske

y 22

Sa

ra R

iver

–GFR

Junc

tion

capt

ured

54

brum

bies

M

id n

orth

-wes

t re

gion

Abo

omal

a H

omes

tead

, 6.5

km

eas

t of G

uyra

19

30s

Brum

by m

uste

r w

ith 2

50 b

rum

bies

from

G

enev

ieve

N

ewbu

ry

21

Padd

ys L

and

sold

or

brok

en

Mor

ning

ton

Stat

ion

to B

oban

Top

s/H

ut a

rea

1930

s Pr

oper

ty o

wne

rs p

aid

on a

per

-hea

d ba

sis

Le

s H

ume

22

for

brum

bies

sho

t as

a m

eans

of c

ontr

ol

Parg

o an

d Bo

bs C

reek

MZs

19

40–1

970

Reca

lls a

lway

s br

umbi

es in

that

are

a, m

axim

um o

f 50

hors

es

Erni

e M

aske

y 36

Bo

bs C

reek

, Com

bolo

and

Bob

an T

ops/

Hut

19

44–4

6 Re

calle

d ri

ding

in th

e ar

ea a

nd s

eein

g go

od q

ualit

y ho

rses

Ja

ck G

iles

24

Balla

rds

Flat

on

Sara

Riv

er, a

djac

ent t

o

mid

194

0s

Dou

g M

eyer

and

two

othe

rs r

ecal

l run

ning

bru

mbi

es h

ere

Dou

g M

eyer

36

Bo

bs a

nd P

argo

Cre

ek M

Z M

orni

ngto

n St

atio

n to

Bob

an T

ops/

Hut

are

a 19

45–1

965

Mrs

New

bury

had

mob

s of

bru

mbi

es a

nd

Flet

cher

Bra

zier

24

w

ould

not

allo

w th

em to

be

shot

unt

il dr

ough

t of 1

965

Chap

ter

2. S

tudy

Are

a 3

1

Tabl

e 2.

3 co

ntin

ued.

Loca

tion

Ye

ar

Obs

erva

tion

/com

men

t So

urce

Pa

ge n

o.

Mid

nor

th-w

est

regi

on c

onti

nued

M

t Won

ga F

lat o

n Pa

ddys

Pla

teau

MZ

1957

20

Bru

mbi

es s

ight

ed

Flet

cher

Bra

zier

24

Pa

rgo

Flat

, abo

ve P

argo

Cre

ek M

Z an

d

1959

17

Bru

mbi

es s

ight

ed

Flet

cher

Bra

zier

36

ad

jace

nt to

Pad

dys

Plat

eau

MZ

Mor

ning

ton

Stat

ion

to B

oban

Top

s/H

ut a

rea

1970

Pr

oper

ty s

tock

ed w

ith 4

0 ho

rses

that

mat

ed w

ith b

rum

bies

Er

nie

Mas

key

22

due

to la

ck o

f fen

ces

Bost

obri

ck S

tatio

n, 3

5 km

eas

t of G

FR

1880

s

Brum

bies

bre

d in

larg

e nu

mbe

rs w

ith fr

ee a

cces

s to

Er

ic F

ahey

19

or

igin

ally

par

t of G

uy F

awke

s St

atio

n th

ousa

nds

of a

cres

la

te 1

940s

H

orse

s fr

om T

he A

ustr

alia

n Li

ght H

orse

Bri

gade

turn

ed

Gly

nne

Tosh

41

ou

t int

o th

e G

uy F

awke

s ar

ea

Pant

ons

Cree

k to

Com

bolo

Sta

tion

1936

–37

Catt

le m

uste

r, n

o br

umbi

es s

ight

ed

Flet

cher

Bra

zier

24

in

the

Kitt

ys C

reek

MZ

area

G

FS a

nd L

GFS

18

90s

2 St

allio

ns, b

red

exte

nsiv

ely

for

over

seas

mar

ket

Er

ic F

ahey

18

e.

g. r

emou

nt tr

ade

for

Briti

sh A

rmy

in In

dia

Won

gwib

inda

Sta

tion

1920

s–30

s Th

ere

wer

e m

any

brum

bies

on

the

prop

erty

that

mus

t hav

e

Phill

ip W

righ

t 21

ex

iste

d fo

r a

num

ber

of y

ears

and

wer

e co

ntro

lled

by

shoo

ting

or tr

appi

ng fo

r st

ock

hors

es

Dya

mbe

rin

Stat

ion

1920

s 2

Stal

lions

for

bree

ding

, unk

now

n if

prog

eny

Pe

ter

Gow

er

22

beca

me

wild

in th

e Pa

rk a

rea

Braz

ier

fam

ily p

rope

rtie

s on

Pan

tons

Cre

ek

1920

–199

0s

Braz

iers

bre

d th

eir

stoc

k ho

rses

und

er ti

ght c

ontr

ol,

Flet

cher

Bra

zier

24

an

d fr

om ju

st a

bove

Lon

don

Brid

ge to

no

esc

apes

or

inte

r-br

eedi

ng. I

n 19

59 n

o br

umbi

es s

ight

ed

Pant

ons

Cree

k M

Z on

pro

pert

y, b

ut 1

7 ou

tsid

e th

e bo

unda

ry a

t Lon

don

Brid

ge

Won

gwib

inda

sid

e of

Abe

rfoy

le R

iver

at

19

59

Two

brum

bies

cau

ght,

bel

ieve

d to

hav

e be

en h

unte

d

Ian

Lupt

on

25

Kang

aroo

Cre

ek

out b

y Bo

ban

Tops

/Hut

sta

llion

s

Surv

eyor

s Sp

ur o

n A

berf

oyle

Riv

er

1975

Re

calle

d se

eing

bru

mbi

es fo

r fir

st ti

me

on th

e A

berf

oyle

Ri

ver

Dou

g Fe

rris

36

Chapter 2. Study Area 32

Brumbies have been sighted in various locations throughout the Park (Table 2.3), but

almost exclusively in the northern MZs since the 1930s (Heritage Working Party 2002a).

2.3.1 North-western management zones: Paddys Plateau, Bobs Creek, Pargo Creek

On the north-western side, Mornington Station is thought to be the source of

brumbies (to become feral horses) inherited with the gazettal of Paddys Plateau MZ and the

Gulf Country as Park (Figure 2.4). The station ran mobs of brumbies that were not shot or

culled until after the 1965 drought, when horse numbers were reportedly out of control

(Heritage Working Party 2002b) (Table 2.3). During the cull, horses were moved into the Gulf

Country and onto the GFR, in particular. Mornington was purchased by Ernie Maskey in 1970

and was stocked with at least 40 of his own stock-horses that inter-mingled with brumbies as

the country was un-fenced. Mornington included parts of Bobs and Pargo Creek (i.e. Gulf

Country) and Paddys Plateau MZs, in which the Boban Tops/Hut is situated (Figure 2.4).

Stock-horses and brumbies were known to be bred and consistently present in those MZs

and were the target of brumby running since the 1930s (Ernie Maskey pers. comm. in

MacDougall 2001) (Table 2.3). Around the 1930s, for example, locals were paid to shoot

brumbies on Boban Tops/Hut (Table 2.3) to control their numbers. The northern sections of

Bobs Creek MZ adjacent to the Sara River MZ both received a flow of horses and brumbies

from Broadmeadows Station along the Boyd River to the Sara River–GFR Junction (Heritage

Working Party 2002b). Given the proximity along the Sara River flats to the mouth of Pargo

Creek to Bobs Creek, brumbies probably continued into Pargo Creek MZ, which also received

an influx of horses from stations in the Mitchell Run on the Henry River to the west

(Figure 2.4). The Heritage Working Party concluded based on sightings and first-hand

accounts that horse numbers were consistent, but low, after the 1940s relative to an

apparent substantial increase in the early 1980s (Heritage Working Party 2002a). Thus,

brumby history was considered to be long with a greater number of horses in Figure 2.4.

Chapter 2. Study Area 33

Figure 2.4 Map of key locations mentioned in Table 2.3 and Section 2.2 and summarised into three levels of length of brumby occupation (minor, intermittent and long) combined with relative number of horses (low, medium and high). Notation as for Figure 2.3.

Chapter 2. Study Area 34

2.3.2 Northern-to-mid-north-eastern management zones: Lower Guy Fawkes River,

Kittys Creek, Mid Guy Fawkes River, Combolo, Marengo

The Brown family established three stations that encompassed what are now the five

aforementioned northern to mid-north-eastern Mzs of the Park, which have had an

uninterrupted grazing history since at least the 1870s (MacDougall 2001). From north to

south, Broadmeadows Station was occupied in 1861, Combolo Station in 1884 and Marengo

Station around 1850–1876 (Figure 2.4). It is thought that the Brown family bred the majority

of brumbies in those areas of the Park in the early 1900s (Heritage Working Party 2002b).

Oral history accounts suggest that brumby populations fluctuated more than in the areas

that are now the north-western MZs (Section 2.2.1), and thus were considered to have an

intermittent history in Figure 2.4. Brumbies were common up until the drought and

subsequent bushfires of 1915, when most succumbed to starvation (MacDougall 2001). The

MacDougall family purchased Marengo in 1895, and captured what were thought to be the

last of the Brown family’s brumbies in 1933 at Peak Creek in Kittys Creek MZ (Table 2.3). By

the mid-1940s to 1970s brumbies were beginning to re-appear in Kittys Creek, Marengo

Creek (including Housewater Creek) and Combolo MZs but sightings and first-hand accounts

were rare until after 1970 (Table 2.3) (Heritage Working Party 2002a).

2.3.3 Southern management zones: Aberfoyle, Kangaroo Creek and Pantons Creek

Brumbies were a common sight on Wongwibinda Station adjacent to Kangaroo

Creek MZ in the 1920–30s when they were controlled by shooting and trapping (Table 2.3).

Similarly, Dyamberin Station had a history of breeding stock horses in the 1920s and it is

unknown if horses escaped to become brumbies (MacDougall 2001). Since the 1950s, just

two sightings of a total of three brumbies in Kangaroo Creek and the Aberfoyle River MZs

were believed to have come from Boban Tops/Hut (Heritage Working Party 2002b). It

appears that the early settlement stock-horses and brumbies did not persist in these areas

and domestic horses on neighbouring pastoral properties have been contained since

(Heritage Working Party 2002a). Thus brumby history was considered to be nil to minimal in

these areas in Figure 2.4.

Chapter 2. Study Area 35

2.4 Feral horse history of monitoring and control in GFRNP

2.4.1 Monitoring prior to the October 2000 cull (1981–2000)

NPWS conducted helicopter-surveys of cattle and horses in a standardised manner,

with flight paths following a zig-zag pattern along the rivers, creeks and adjoining slopes, as

flat ground is generally only associated with the riparian flats (Heritage Working Party

2002a). Feral horses are more visible in such areas and tend to head to open, flat areas when

mustered. The early helicopter-surveys (1981–82) were opportunistic counts of horses

whilst monitoring cattle incursions. Thus, surveys were biased towards the mid-eastern MZs

containing a greater proportion of the GFR flats, and other tracts of flat ground such as the

Fattening Paddock (Figure 2.5). Pantons Creek, Pargo Creek and the southern half of Bobs

Creek were not yet gazetted, and as the Sara River and northern Bobs Creek MZs were not

commonly utilised by cattle, they too were not surveyed (Table 2.4). In 1981–82, a greater

number of horses were counted in the Lower GFR, followed by Mid GFR and Kittys Creek MZs

with nil to minimal horses in the south-eastern MZs (Table 2.4). After December 1996,

Pantons Creek MZ was included in all but one survey as it was small in size, oriented north–

south, continuous with GFR and required little additional effort (Figure 2.5). According to

local stockmen and NPWS field staff, horses were not present in Kangaroo Creek MZ, and

incursions were minor in the Aberfoyle River MZ, tending to be limited to the GFR Junction.

Helicopter-surveys in December 1998 recorded no horses in both MZs (Table 2.4), with the

result repeated for Kangaroo Creek MZ in May 2004 (Table 2.5). A total of six horses were

counted in the Aberfoyle River MZ in the October 2000 cull (Table 2.5), again at the GFR

Junction, perhaps fleeing into the area in response to the helicopter (Figure 2.6).

In the December 1996–98 helicopter-surveys, more horses were counted in the Mid

GFR and Kittys Creek MZs. In the 1996 and 1997 helicopter-surveys, Bobs Creek itself was

included (Figure 2.6). In 1998, only the small area of Bobs Creek MZ that adjoins the Sara

River MZ was surveyed and not the creek itself, which may explain the lower counts

(six horses) relative to previous years (11–15 horses) (Table 2.4). During this period, as

explained in Table 2.1, Bobs Creek MZ was much smaller (1100 ha) than the other MZs with

horse populations. In 1998, only a relatively small stretch of the Sara River MZ (from GFR

Junction to the mouth of Bobs Creek) was surveyed for the first time, with the number of

horses counted comparable to Combolo and Lower GFR MZs (Table 2.4).

In May 2000, in addition to the eight MZs in which horses had previously been

counted, Pargo Creek was gazetted and included in the total count of 180 horses (Table 2.4).

Chapter 2. Study Area 36

Five months later, an additional 103 horses were counted in the same areas with one less

MZ, Kittys Creek, where previous counts had been high (Figure 2.6). Kittys Creek MZ was not

included as counts were made on 18 October 2000 during wild fire control operations and

the survey was restricted to the valleys adjacent to the GFR and Sara River (Heritage Working

Party 2002a). The GFR flows around Kittys Creek MZ through the Mid GFR MZ (Figure 2.5).

The wild fire burnt almost 60% of the Park area from early September (English 2000) and may

have been less intense on the green river flats adjacent to permanent water, leading to the

concentration of horses in those areas.

Table 2.4 Summary of the number of horses counted in each management zone (MZ) and total number of horses across the Park from helicopter-surveys conducted by NPWS Dorrigo Plateau Area office, from 1981 to prior to the cull in 2000. The 2000 helicopter-survey shapefiles had Global Positioning System (GPS) coordinates but no accompanying number of feral horses in the mob and thus were combined (Comb.) for the MZs surveyed. NG: not yet gazetted as Park, NS: not surveyed, '–' indicates a missing data entry, (no information available).

MZ code MZ name

Dec. 1981

June 1982

Dec. 1996

Dec. 1997

Dec. 1998

May 2000

Pre-cull survey

Oct.2000

1 Pantons Creek NG NG 0 0 0 0 NS 2 Upper GFR 2 0 7 6 1 Comb. Comb. 3 Marengo 0 0 2 0 5 Comb. Comb. 4 Aberfoyle River NS NS NS NS 0 NS NS 5 Combolo 2 1 17 0 17 Comb. Comb. 6 Mid GFR 27 – 90 47 53 Comb. Comb. 7 Kittys Creek 18 12 52 52 30 Comb. NS 8 Paddys Plateau NS NS NS NS NS NS NS 9 Bobs Creek NS NS 11 15 6 Comb. Comb.

10 Pargo Creek NG NG NG NG NG Comb. Comb. 11 Sara River NS NS NS NS 21 Comb. Comb. 12 Lower GFR 39 34 NS NS 19 Comb. Comb.

13 Glen Nevis Plateau NS NS NS NS NS NS NS

14 Kangaroo Creek NS NS NS NS 0 NS NS Total number of horses 88 47 179 120 152 180 283

Chapter 2. Study Area 37

Figure 2.5 GPS location of horse mob sightings from helicopter-survey counts in Table 2.4, showing the distribution of horses in MZs in relation to rivers and creeks. Notation as for Figure 2.3.

Chapter 2. Study Area 38

2.4.2 Management pre and post-cull, and monitoring post-cull (2000–2007)

From 1972 to the early 1990s, horses in the Park were not managed (NSW NPWS

2006b). As substantial areas were added to the original 1972 Park extent, graziers left with

most of their cattle and horses but due to the expansive rugged terrain and minimal fencing,

some horses remained (Ballard 2005). It is also the general opinion of local graziers that

brumbies were bred to be strong, and with no natural predators and local management, in

those ensuing years the populations increased to numbers larger than those recalled for the

period 1900–1965 (MacDougall 2001).

Active management of the horse population began in 1992. Various methods were

trialled, but up until 2000, horses were trapped and mustered predominantly by men on

horseback, occasionally assisted by helicopter (NSW NPWS 2006b). Over that period,

156 horses were removed from the Park, mostly from Broadmeadows along the Boyd River

and GFR in the Lower GFR, Kittys Creek, Combolo and north-eastern corner of

Bobs Creek MZs (D. O’Brien and G. Baldwin pers. comm.).

The largest control operation in the Park occurred on 22–24 October 2000 when a

total of 606 horses were culled from helicopters (English 2000). Of the 606 horses shot,

373 horses were assigned a specific GPS coordinate. Given that 41 ‘unknowns’ were in the

Mid GFR MZ compared to ≤four unknowns in any other MZ, it can be assumed that almost all

of the remaining 233 horses were in the Mid GFR. This assumption was also consistent with

the 1981–2000 helicopter-surveys where horse counts tended to be greatest in the

Mid GFR MZ from 1996–1998 (Table 2.4). Kittys Creek and Bobs Creek MZs recorded a

similar and the next largest number of kills. The density of kills would have been much

greater in Bobs Creek MZ as in Figure 2.6 only the northern section was included in the cull

(1100 ha) while the entire Kittys Creek was surveyed (3700 ha). Similarly, in the

Sara River MZ, the cull focused on the eastern half along the Sara River, with approximately

half the number of kills as Bobs and Kittys Creek MZs.

Chapter 2. Study Area 39

Figure 2.6 GPS location of horse mob sightings corresponding to helicopter-survey counts showing the distribution of horses in management zones in relation to rivers and creeks for the 22–24 October 2000 cull (Table 2.5) and for the comprehensive 2006 helicopter-survey. Notation as for Figure 2.3.

Chapter 2. Study Area 40

Table 2.5 Summary of the number of horses shot (October 2000 only) or counted (2001–2005) in each management zone (MZ) and total number of horses across the Park. Survey method as in Table 2.4. UK: unknown number of horses in the mob shot at that location, only GPS coordinate provided, NS: not surveyed.

MZ code MZ name 22–24 Oct. 2000 cull

April 2001

May 2004

7 April 2005

12 April 2005

1 Pantons Creek 0 NS 0 NS NS 2 Upper GFR 5 (1UK) NS 9 NS NS 3 Marengo 12 NS 0 NS NS 4 Aberfoyle River 6 NS NS NS NS 5 Combolo 8 5 0 NS NS 6 Mid GFR 64 (41UK) 3 14 NS NS 7 Kittys Creek 79 (2UK) NS 3 NS NS 8 Paddys Plateau NS NS 29 NS NS 9 Bobs Creek 89 27 23 62 46

10 Pargo Creek 11 16 20 54 33 11 Sara River 44 16 15 NS NS 12 Lower GFR 7 (4UK) NS 9 NS NS

13 Glen Nevis Plateau NS NS 0 NS NS

14 Kangaroo Creek NS NS 0 NS NS

Total number of horses 373 (606 including

UKs) 67 122 116 79

Paddys Plateau was exempt from the cull as it is one of the few MZs with vehicle and

public access, and is surrounded by a number of grazing properties. Hence, the estimated

80 horses that remained after the cull (English 2001b) were concentrated mostly on Paddys

Plateau. It is thought, based on NPWS field staff observations, the presence of extensive

horse track networks and ground survey counts by Schott (2003), that numbers of horses

move seasonally between the eastern half of the Sara River, Bobs and Pargo Creek, and

Paddys Plateau MZs (NSW NPWS 2006c). The April 2001 helicopter-survey after the cull

therefore focused on those three MZs and the Mid GFR where kills during the cull were

concentrated (and Combolo MZ due to proximity and inclusion of the GFR). Counts were

greatest in Bobs Creek MZ (27 horses), and equal in Pargo Creek and the Sara River MZs

(16 horses), and comparatively low in Mid GFR MZ with just three horses counted and

five horses in Combolo MZ. This result was consistent with the seasonal migration

mentioned previously for the western block of MZs and suggests that, in the period

immediately after the cull, horses re-colonised Bobs Creek, Pargo Creek and the Sara River

MZs. The trend continued in the May 2004 helicopter-survey, which included the additional

four MZs with historical counts of horses. Counts were greater in the western block of MZs,

with no horses counted in Combolo and Marengo and just three horses in Kittys Creek.

Chapter 2. Study Area 41

Paddys Plateau was included for the first time and an additional six–nine horses were

counted than in Bobs and Pargo Creek MZs. However, Paddys Plateau is 2–3.7 times greater

in area than Bobs Creek and Park Creek, thus the density of horses was greater in the latter

MZs. In support of this assessment, Bobs and Pargo Creek were selected by the NPWS

Dorrigo Plateau Area office and Vernes et al. (2009) for a novel mark–recapture technique to

estimate peak feral horse densities in the Park. As the southern half of Bobs Creek had been

gazetted in 2000 the entire MZ was surveyed in the 2005–2007 helicopter-surveys. From the

7 and 12 April 2005 helicopter-surveys, a total of 164 individual horses were photographed

and identified and the combined density of horses in Bobs and Pargo Creek MZs estimated at

0.038 horses/ha (upper and lower 95% confidence limits [CL] = 0.035–0.057 horses/ha). The

technique was repeated in May 2006 and 2007. In 2006 a total of 115 individual horses were

identified but recaptures were insufficient to estimate density. The 2006 survey also

included the Sara–GFR Junction, Kittys Creek and the MZs associated with the GFR. The

largest number of mobs and horses were again counted in Bobs and Pargo Creek MZs

(Figure 2.6). In 2007, the portion of the Sara River MZ along the Sara River that adjoins Bobs

and Pargo Creek MZs was included with a total of 236 individuals identified and density

estimated at 0.023 horses/ha (CL, 0.021–0.034 horses/ha). The change in density from 2005

to 2007 followed horse control (passive trapping and removal) on the Sara River at Ballards

Flat and upstream of the Sara River–Bobs Creek Junction.

2.5 Recent history of cattle incursions in GFRNP

Feral cattle and horses have been concurrent management issues, with 151 cattle

sighted in addition to the 283 horses along the Sara–GFR Junction flats and the flats of the

GFR in the 18 October 2000 helicopter-survey. The MZ, number of cattle in each mob and

total number of cattle sighted in MZs in the Park in 1995, 1997, 1998 and 1999 are

summarised in Table 2.6 and the specific GPS locations provided in Figure 2.7. Both

represent the typical distribution patterns of cattle in the Park prior to the start of this

project. Cattle mobs have been mostly associated with riparian flats adjacent to the Boyd

River and mid to lower GFR, and with the higher plateau country in the vicinity of the

Fattening Paddock (Figure 2.7). More often than not, multiple mobs of cattle were counted

in Combolo and Upper GFR MZs in all four survey-years, with a peak MZ total of 171 cattle in

Combolo in 1998. The Fattening Paddock (within GFR State Conservation Area) did not

record cattle every survey-year, but totals were relatively high (70 and 204 cattle). Cattle

Chapter 2. Study Area 42

incursions were also reasonably frequent with some large mobs (e.g. 80 cattle in 1998,

Table 2.6) in Marengo MZ, and to a lesser extent in the Mid and Lower GFR MZs.

Table 2.6 Summary of NPWS Dorrigo Plateau Area office helicopter-survey counts of cattle mob incursions in the Park in 1995–1999, corresponding to Figure 2.7. Individual numbers separated by a comma represent the number of cattle in one mob per GPS location with the total number of cattle per management zone (MZ) each year in bold and parentheses.

Several local stockman who ran cattle in the Park or in similar country (e.g. Brian

Fahey, Doug Ferris) and NPWS field officers and rangers (Tony Prior) were of the opinion that

cattle activity was concentrated on the riparian flats and adjoining lower slopes along the

major river systems, and cattle had to be forcibly mustered up moderate (6–18°) or steep

slopes (18–30°) (McDonald et al. 1990). The GPS locations of cattle mobs in Figure 2.7 were

overlayed on a raster slope grid that was classified into four slope classes. As predicted,

almost all cattle sightings were associated with flat or gently sloping ground (<10°).

Cattle counts in the Aberfoyle River were limited to the GFR Junction area (Figure 2.7)

and coincided with several letters of complaint from bush-walkers at the Aberfoyle–GFR

Junction in the mid-1990s. No cattle were sighted in Pargo Creek MZ, and just the one mob

of 6 cattle in Bobs Creek MZ along the creek (Table 2.6). Cattle in the Sara River MZ tended

to favour the larger Ballards Flat area (Figure 2.7) or flats along the Sara River and rarely

strayed up into the precipitious Bobs and Pargo Creeks, the entrance being obscured by a

rocky cliff in Pargo Creek MZ. Similarly, the Brazier family own land adjacent to the Park and

in 2009 sold the Pargo Flat parcel on the elevated plateau above Pargo Creek MZ to the

NPWS (Figure 2.7). Pargo Flat was optimal for grazing cattle but mostly adjoins Pargo Creek

MZ along a sharp, rocky cliff that prevents cattle from accessing the MZ (Terry Brazier pers.

comm.).

MZ Code Management Zone 1995 1997 1998 19992 Upper GFR 7, 7, 11, 33 (58) 3, 6, 8, 23 (40) 50 11, 41 (52)3 Marengo 0 4, 5, 9, 9, 9 (36) 80 524 Aberfoyle River 0 5, 5 (10) 97 05 Combolo 1, 6, 12, 14 (33) 8, 12, 60 (80) 34, 40, 97 (171) 236 Mid GFR 5 12, 12, 15, 16, 16 (71) 0 07 Kittys Creek 4 0 0 169 Bobs Creek 0 0 0 6

10 Pargo Creek 0 0 0 011 Sara River 6, 10, 18 (34) 0 0 1212 Lower GFR 52 0 0 20

Fattening Paddock 0 10, 18, 21, 21 (70) 5, 5, 14, 15, 15, 20, 50, 80 (204) 0

Chapter 2. Study Area 43

Pantons and Kangaroo Creek MZs were not included in helicopter-surveys even

though both MZs had a history of and still incur periodic cattle incursions from neighbouring

pastoral holdings. Instances of cattle incursions have become minimal in the last 10–

20-years with generational change (Tony Prior pers. comm.). Only a few remaining stockman

are willing and able to camp and muster cattle remotely for any length of time. According to

neighbouring pastoral property owners, encroachment is also limited temporally and

spatially, occurring over winter with mobs of cattle of between 20 and 50 beasts and on the

same few select routes (Doug Ferris and Andy Winkle pers. comm.).

The western section of Paddys Plateau MZ adjoins grazing properties but is well

fenced and has one of the Park’s few developed vehicle tracks. Cattle incursions have

occurred on occasion south-west of Wonga Hut, but given the proximity to the Tallagandra

depot and good access, NPWS field staff have quickly yarded and removed cattle once

sighted. NPWS staff confirmed that there were no records or known instances of graziers

droving cattle into Pargo or Bobs Creek since 1972, consistent with oral histories that

confirmed cattle were not run in Bobs and Park Creeks MZs prior to 1972.

Chapter 2. Study Area 44

Figure 2.7 GPS locations of cattle mob sightings in the Park in 1995 and 1997–1999 overlayed on a slope classification. Notation as for Figure 2.3.

Chapter 2. Study Area 45

2.6 Selection of management zones for the landscape-scale survey (Chapter 6)

The catchment survey was conducted at a landscape scale corresponding to the size

of the MZs or catchments. It required two catchments occupied by horses to represent the

‘horse’ (H) level of the Treatment factor, and two catchments to represent the ‘non-horse’

(N-H) level. If possible, all catchments would also have nil to minimal cattle use, both past

and present. Of the 14 MZs, nine have been populated by horses to some extent with the

total area of declared Wilderness in the Park under feral horse occupation estimated at

34 000 ha (40%) in 2006 (NSW NPWS 2006c). From Sections 2.1–2.5, the prime candidates

for the horse catchments were Bobs and Pargo Creek. Both have one of the longest and

most consistent history of horses, and the greatest density of horses after the 2000 cull to

the present day. Just as importantly, the relative scarcity of riparian flats and their smaller

size made them unsuitable for cattle and on the whole, these catchments were not used by

graziers for running mobs of cattle during any period since European settlement. The Mid

GFR MZ would have been suitable in terms of horses, but was confounded by the presence of

cattle, as were parts of the Sara River, Combolo, Upper and Lower GFR and Marengo MZs.

Cattle incursions into Kittys Creek MZ appeared minimal, but the early horse history was

intermittent and horses did not re-colonise the area to the same extent as Bobs and Pargo

Creeks after the cull.

From Sections 2.1–2.5, candidates for the non-horse catchments were Kangaroo and

Pantons Creek. Kangaroo Creek and Pantons Creek MZs, in particular, had no history of feral

horses, and minimal history of brumby and stock-horse use. The Aberfoyle River MZ was

considered, but potentially had some brumby and feral horse use in the late 1960s to late

1980s. In all three MZs, cattle incursions occurred occasionally but were not of intensity

(cattle numbers) or frequency to attract sufficient attention.

Chapter 3. Indirect Effects on Macropods 46

CHAPTER 3.

INDIRECT EFFECT OF FERAL HORSES ON THE SPATIAL DISTRIBUTION OF MACROPODS

3.1 INTRODUCTION

In Australia, feral horses may compete with wildlife, notably macropods, for food,

water and space (Olsen and Low 2006; Nimmo and Miller 2007), but the evidence is

equivocal. In the Northern Territory (NT), Berman and Jarman (1988) reported a negative

correlation between the presence of macropod dung and horse dung at some sites and

concluded that by removing the herb layer, both horses and cattle appeared to influence

wildlife. However, replication was limited to one site with horses and no cattle and cattle

and macropod dung were negatively correlated at all other sites (Berman 1991). Similarly,

after 6000 feral horses were removed from Finke Gorge National Park in central Australia,

the amount of fresh black-footed rock wallaby (Petrogale lateralis) dung was observed to

steadily increase from zero over a period of 10 years (Matthews et al. 2001). While the

correlation was ‘striking’, cause (horse removal) and effect (increase in rock wallabies) could

only be inferred (Matthews et al. 2001). The study was uncontrolled and unreplicated and

no data were presented or available upon request (Edwards et al. 2003; Glenn Edwards, pers.

comm.). In the west MacDonnell Ranges, NT, the historically rare central rock-rat (Zyzomys

pedunculatus) was presumed extinct in 1990 after not being recorded for 36 years, but was

rediscovered in 1996, with 40 individuals live-trapped at 11 sites since then (Nano et al.

2003). The authors speculated that the recent increases in abundance of the central rock-rat

were due to the removal of more than 30 000 feral horses from the west MacDonnell Ranges

over the past 15 years (Bryan 2001). In GFRNP, after 606 horses were culled in

October 2000, eastern grey kangaroos (Macropus giganteus) were observed by NPWS staff

to rapidly colonise the grassy river flats in ‘unprecedented numbers’ (Tony Prior, pers. comm.

in Olsen and Low 2006). The first three studies mentioned previously are assumed to reflect

resource or exploitative competition given they were in semi-arid environments where

resources tend to be limited and localised (Noy-Meir 1973; Caughley 1987). In the case of

the central rock-rat, the major food plants identified in their diet were also palatable to

stock, including horses (Nano et al. 2003).

In riparian flush zones and around watering points in semi-arid environments, feral

horses remove almost all available herbaceous biomass (Beever and Brussard 2000a; Seliskar

2003). In the USA, key resource locations are where resource and indirect interference

Chapter 3. Indirect Effects on Macropods 47

competition between both feral horses and feral burros (Equus asinus) and native ungulates

such as desert bighorn sheep (Ovis canadensis) are most likely to occur (Dunn and Douglas

1982; Berger 1985, 1986; Marshal et al. 2008; Ostermann-Kelm et al. 2008). Manipulative

field experiments to test the mechanism underlying competitive relationships are rare

because they are notoriously difficult and can be expensive to implement under natural

conditions (Stewart et al. 2002). The potential for exploitative competition is thus inferred or

modelled on the degree of overlap in feeding strategies and diet, as significant overlap in

resource utilisation invariably leads to competition and the competitive exclusion of some

species (Pulliam 1986).

Regardless of the mechanism involved, an overlap in species’ habitat preferences is a

necessary precursor to interspecies interactions (Araujo and Luoto 2007) and patterns of

habitat use in grassy woodland appear to be very similar for feral horses and eastern grey

kangaroos. Both select alluvial grasslands with a mixture of forbs and short grasses or mesic

flush zones in hillside depressions (gully lines), followed by open grassy woodland, and both

avoid habitats with dense, shrubby undergrowth (Taylor 1980; Landsberg and Stol 1996;

Walters 1996; Linklater et al. 2000; Veltman 2001; Lamoot et al. 2005). Dung is an indirect

method used to infer the presence of an animal in an area (Wilson and Delahay 2001; Sadlier

et al. 2004). Dung counts have been used to determine the grazing distribution of horses and

eastern grey kangaroos as both species defecate where they graze (Hill 1981; Johnson and

Jarman 1987; Walters 1996; Lamoot et al. 2004). In the present study, the NSW NPWS

commissioned a horse capture and removal program that provided an opportunity to assess

changes in macropod dung in relation to the manipulated abundance of horses. Dung

transects were monitored at the district scale (100 ha) in Paddys Plateau catchment, at the

site (0.01 ha) and district scale (4 × 1 km) in Bobs Creek catchment, and at the catchment

scale (5000 ha) to determine if the removal of horses coincided with increased macropod

activity. If so, it would provide support for the hypothesis that horses affect the feeding

distribution of macropods.

Chapter 3. Indirect Effects on Macropods 48

3.2 METHODS

3.2.1 Paddys Plateau dung transects and horse removal program

3.2.1.1 Dung transect zones

For the Paddys Plateau exclosure experiment, six sites were selected >1 km from

each other. Information in Chapter 2 on horse distributions and seasonal movement

patterns, NPWS field staff experience and knowledge, and personal observation suggested

that sites were located along a grazing gradient. Sites 1, 2 and 3 were located in the mid-

section of the Plateau between the Aberfoyle River catchment, which did not have a resident

horse population, and the south-western tip of Bobs Creek catchment (Figure 3.1). No

horses have been sighted or shot in the south-western tip of Bobs Creek (Chapter 2,

Figure 2.5 and 2.6). Sites 4, 5 and 6 in the eastern section of Paddys Plateau were separated

from Sites 1–3 by a narrow spur. The eastern section was adjacent to three horse-occupied

catchments: the mid to northern section of Bobs Creek, the southern half of Kittys Creek, and

the south-western tip of Combolo (Figure 3.1). Kittys Creek tributary runs back into the

Boban Hut area, and was thought to be a historical migration conduit for brumbies (and later

feral horses) prior to the 2000 cull (MacDougall 2001). In the recent May 2006 heli-survey,

horses were not sighted within 4 km of the Paddys Plateau and Kittys Creek catchment

boundaries (Figure 2.6). However, horses were sighted near the Travelling Stock Route (TSR)

adjacent to Site 4 that connects Combolo catchment to the Boban Hut area (Figure 3.1). The

TSR continues on from Boban Hut along the escarpment edge of Bobs Creek. The dung

transects for Sites 5 and 6 were next to the Bobs Creek escarpment, which overlooks Bobs

Creek and is connected to the other catchments with high densities of horses after the cull,

Pargo Creek and the Sara River flats (e.g. Ballards Flat) (Figure 3.1). Visual inspection of the

two catchments confirmed the presence of an extensive, well-developed or worn horse track

network (based on degree of soil surface hardness, depth and width of track and signs of

sheeting or gully erosion) connecting them. Several reports had also documented a high

concentration of signs of horse activity, such as bark-chewing on trees and well-worn salt

licks (salt deposits that herbivores regularly lick to obtain mineral nutrients such as calcium,

sodium and iron; Kreulen 2008) in the area (Schott 2002, 2003; Ashton 2005). Horses may

use the Paddys Plateau–Bobs Creek migration conduit either to obtain nutrients or to find

mates in the case of dispersing off-spring, in addition to the seasonal migration discussed in

Chapter 2. Site 5 (Boban Hut) appeared to be the central point of dispersion for migrating

horses, followed by Site 6 (Spion Kiope). Both sites were named after their proximity to

Chapter 3. Indirect Effects on Macropods 49

trapping yards by the same name (Section 3.2.1.3). In addition, once trapping started, horses

were not removed at the Boban Hut trap site until 5 months later (September 2004) than the

trap sites associated with Sites 1–3 (April 2004), and at Spion Kiope later still (October 2005).

Thus, horse grazing pressure was potentially greater historically in and around Sites 4–6 and

greater during the experiment, with horses persisting longer in Sites 4–6 than Sites 1–3 after

the commencement of the trapping program in April 2004.

3.2.1.2 Dung transect design and monitoring

Twelve permanent dung transects were established in a dung transect zone

surrounding each of the six exclosure sites on 1–9 July 2005. Transects were monitored an

additional three times: 7–12 November 2005, 12–18 March 2006 and 13–19 July 2006. On a

topographic map (Kookabookra 9337-IV-N, 1:25,000), the 100-ha Universal Transverse

Mercator (UTM) grid containing the exclosures for Sites 1–3 were selected as the dung

transect zone for the corresponding site (Figure 3.1). For Sites 4–6, grids containing

exclosures bordered each other. Spatial separation or independence between dung

transects zones was obtained by selecting an adjacent grid (Figure 3.1). The starting points of

dung transects within the 100-ha grid were chosen randomly using the Random Generator in

Excel 2003. The compass orientation of the transect line was determined the same way.

Dung transects were 50-m long and dung deposits recorded 5 m either side of the transect in

a quadrat of 0.05 ha.

Chapter 3. Indirect Effects on Macropods 50

Figure 3.1 Location of exclosure sites and dung transect zones relative to trap sites and the Bobs Creek Sara River migration conduit. The termination point of Bobs Creek tributary and the topography of Paddys Land relative to neighbouring catchments are shown using multispectral SPOT 5 imagery. The SPOT 5 image was captured on 26 May 2005; pixel resolution is 10 m (DNR 2005).

Dung of the large grazing herbivores of interest, horses and macropods, was counted

and then raked clear of the transect line. A dung pile (referred to as a deposit) consisted of

numerous individual pellets of horse or macropod dung. Horse dung was counted as one

deposit as long as pellets were grouped together in one pile or if there was a pile of decayed

dung, even without discernable pellets. Individual scattered pellets associated with an

adjacent dung deposit were not counted. Macropod dung was counted if pellets were

grouped into one pile or if there were one or two individual pellets not clearly associated

with, or located next to, another dung deposit. Otherwise pellets were judged to be

separate deposits on the basis of distance, pellet size, shape and age according to Hill (1978).

The different detection probabilities associated with horse and macropod dung were

recognised and controlled for at the outset of the experiment. Horse dung deposits were

large and immediately visible to the naked eye from a distance. Macropod dung was smaller

and could be covered or camouflaged by litter or tussock foliage. Thus, an intensive search

protocol was used for macropod dung (e.g. a stick was used to scratch through shallow litter

Chapter 3. Indirect Effects on Macropods 51

piles and dense piles of leaf litter, bark or tussock vegetation was searched by hand). Any

objects similar to macropod pellets, such as rocks and dirt or seed pods, were examined and

sometimes checked by crushing them.

The most abundant macropod species on the plateau and in the Park was the eastern

grey kangaroo, followed by the red-necked wallaby (Macropus rufogriseus) (NSW NPWS

2009a and K. Vernes pers.comm.). Eastern grey kangaroo deposits were distinguished from

red-necked wallaby pellets after Johnson and Jarman (1987). The approximate time interval

between dung counts was 4 months. Given differences in the size and volume of macropod

and horse dung, it was possible that some macropod dung may have decayed and

disappeared within this interval and was underestimated (Appendix 2).

When transects were established, detailed descriptions were made and

photographs taken of the habitat surrounding each transect, including the dominant

composition and relative density and height of the groundstorey, understorey and canopy

layer. Transects were allocated post-data collection to one of four habitat types: (1) grassy

woodland (GW), (2) shrubby woodland (SW), (3) grassy swale (GS) and (4) track (T).

Grassy woodland (GW) had a groundstorey projective foliage cover of 10–30% and

trees 10–30 m tall, with a well-developed herbaceous stratum in which grasses were

prominent (70–100% cover) and shrubs poorly developed or absent (Figure 3.2). In the

southern half of Australia, this community has been subjected to stock grazing (Specht 1970).

The open structure was easily traversed, and palatable tussock grasses such as kangaroo

grass (Themeda australis), tussocky poa (Poa sieberiana), wild sorghum (Sarga leiocladum),

and barbed wire grass (Cymbopogon refractus) were abundant and accompanied by patches

of the highly palatable, year-long green, perennial grass, weeping grass (Microlaena

stipoides), and legumes such as slender tick-trefoil (Desmodium varians). The other

dominant structural formation on Paddys Plateau was grassy, open forest with a foliage

cover of 30–70% (Specht 1970). The herbaceous stratum was as well-developed and grasses

as prominent (70–100% cover) as grassy woodland but shrub development may have been

slightly greater at times due to the potential for greater shrub recruitment. A few transects

were located in the transition zone between grassy woodland and grassy, open forest.

Chapter 3. Indirect Effects on Macropods 52

Figure 3.2 Grassy woodland dung transect.

Shrubby woodland (SW) transects had the same groundstorey structure and often

extended into grassy woodland, but were distinguished by having ≥50% of the transect in

dense pockets of shrubs usually with a sparser herbaceous layer (Figure 3.3). The abundant

shrubs were dominated by understorey species such as acacias (Acacia spp.), melaleucas or

paperbarks (Melaleuca spp.) and sheoaks (Allocasuarina spp.). At times, the shrubby layer

and seedlings formed dense thickets that were either difficult to traverse or impenetrable.

Some sections of the groundstorey were comprised of rocky infertile soils and patches of

bare ground, some were covered by gap-colonising, carpet-forming forbs such as kidney

weed (Dichondra repens), while others were dominated by fine and coarse litter and woody

debris or less palatable grasses such as blady grass (Imperata cylindrica). Shrubby woodland

transects sometimes had patches of a palatable, grassy, ground layer (Figure 3.4). However,

such vegetation in general was cluttered and the herbaceous biomass was patchy.

Chapter 3. Indirect Effects on Macropods 53

Figure 3.3 Cluttered section of shrubby woodland with a horse in the background.

Figure 3.4 Comparatively open section (foreground) in shrubby woodland.

Grassy swales (GS) occurred in grassy woodland and consisted of open treeless and

shrubless drainage lines and swales; they appeared to have better moisture and fertility

status than adjacent grassy woodland (Figure 3.5a). Weeping grass was more common in

this habitat type than others, and some transects were grazing lawns (Figure 3.5a and b).

Grassy swales were frequently observed being grazed by mobs of macropods or horses.

Chapter 3. Indirect Effects on Macropods 54

Figure 3.5 (a) A grassy swale with a ground layer dominated by weeping grass, adjacent to grassy woodland.

Figure 3.5 (b) A grassy swale consisting of a grazing lawn.

Chapter 3. Indirect Effects on Macropods 55

The final habitat type, ‘track’ (T), referred to transects in one of the three

aforementioned habitat types but which also dissected or ran parallel to a vehicle track

(Figure 3.6). At Site 5, tracks were major horse tracks, which were prevalent; vehicle tracks

were not present in that dung transect zone. Tracks probably incurred more use by horses

than shrubby woodland as they provided an efficient means of moving between areas of the

plateau, for example, to known dam locations or mineral sources.

Figure 3.6 Vehicle track transect in grassy woodland.

As transects were not stratified by but assigned to habitat type post-hoc for the

purpose of analysis, the number of transects in each habitat type differed between zones

(Table 3.1). Grassy (34.7%) and shrubby (33.3%) woodland had the most transects, followed

by grassy swale (19.4%) and track (12.5%). In Sites 1–4, there were generally four to five

transects in grassy woodland, three to four transects in shrubby woodland, and one to

Chapter 3. Indirect Effects on Macropods 56

three transects in grassy swale (Table 3.1). However, in Site 5, six transects were shrubby

woodland and Site 6 had four grassy swale and three grassy woodland transects.

Table 3.1 Number and proportion (in parentheses) of dung transects in each site (12 transects) in the four habitat types. The total number of dung transects in each habitat type was unequal, and are italicised in the bottom row.

Grassy Shrubby Grassy woodland woodland swale Track Site 1 4 (0.33) 4 (0.33) 3 (0.25) 1 (0.08) Site 2 4 (0.33) 4 (0.33) 2 (0.17) 2 (0.17) Site 3 5 (0.42) 4 (0.33) 1 (0.08) 2 (0.17) Site 4 5 (0.42) 3 (0.25) 3 (0.25) 1 (0.08) Site 5 4 (0.33) 6 (0.50) 1 (0.08) 1 (0.08) Site 6 3 (0.25) 3 (0.25) 4 (0.33) 2 (0.17) Total 25 24 14 9

Horse deposits were photographed and described. Descriptions included the number

of intact or recognisable individual pellets, relative size (e.g. small to large pellets >10 cm in

length), presence of vegetation or fungi growing out of the dung deposit, colour and

moisture content, and an assessment of the extent of weathering and decay. Dung counted

at the first sampling time in July 2005, when the dung transects were established, had

accumulated over an undefined period. Subsequent sampling times in November 2005,

March 2006 and July 2006 meant that dung accumulated over approximately 4 months

between each sampling time as the transects were cleared of dung at each reading. In New

Zealand’s Kaimanawa Mountain Range, the average decay time for dung to be no longer

visible from a distance of 1.5 m was 424 ± 34 days with most dung disappearing in just over

1 year (Linklater et al. 2001). Published information on the relationship between the

numbers of intact individual pellets in a dung deposit of different ages was unavailable, but

old dung deposits tended to have the greatest number of plant and fungi species growing

directly in the dung deposit (Loydi and Zalba 2009). In order to compare the July 2005

accumulation period to the subsequent accumulation periods, the average number of intact

individual pellets from dung deposits at June 2006, which was 12 pellets, was used as a

reference point. Any dung deposits with ≤11 intact individual pellets or the presence of fungi

and vegetation were excluded. Of the total dung deposits counted in July 2005, 64.5% were

eliminated and the accumulation period estimated to be an equivalent 4 months.

Chapter 3. Indirect Effects on Macropods 57

3.2.1.3 NSW NPWS capture and removal program

The Dorrigo Plateau Area office of the NSW NPWS initiated a program in April 2004 to

trap and remove horses from Paddys Plateau. The program was repeated in 2005 and 2006.

The trapping program is described in detail and accompanied by a comprehensive summary

of trap records, including demographic data, in Appendix 3. Trap records included the

capture date and location of each horse. Seven trap sites were used (Figure 3.1). Trap sites

at Wonga Flat, Mt Gardiner Plateau and Perrys Yards were closest to Sites 1, 2 and 3 at a

distance of 5–7 km (approximate straight line distance). Ryans Paddock trap site was

between Sites 1 and 2 at a distance of 0.5 km, and Middle Dam trap site was near Site 3.

Spion Kiope trap site was <2 km from Site 6 and Boban Hut trap site was <1 km from Site 5.

Due to the potential difference in horse grazing pressure between Sites 1–3 and

Sites 4–6 and location of trap sites relative to exclosure sites, trap records were summarised

in relation to the two respective groups of trap sites, dung accumulation periods and trap

periods (Table 3.2). Horse captures at Wonga Flat, Perrys Yards, Ryans Paddock, Mt Gardiner

Plateau and Middle Dam were combined and referred to as trap sites 1–3 to reflect their

relative proximity to exclosure Sites 1–3 and respective dung transects. Similarly, horse

captures at Boban Hut and Spion Kiope were referred to as trap sites 4–6 to reflect their

relative proximity to exclosure Sites 4–6 and associated dung transects.

Table 3.2 Protocol used to summarise the NSW NPWS trapping program so that trapping records could be compared with the dung transect results in Table 3.5.

Dung accumulation period Description of period Trap period dates Pre-July 2005 First 6 months of trapping April–September 2004 July 2005 (T1) Estimated 4-month dung November 2004–June 2005

accumulation period November 2005 (T2) First 4-month defined July–November 2005

dung accumulation period March 2006 (T3) Second 4-month defined December 2005–March 2006

dung accumulation period July 2006 (T4) Final 4-month defined April–July 2006

dung accumulation period Post-July 2006 4 months after dung August–November 2006 monitoring had ceased

Chapter 3. Indirect Effects on Macropods 58

The number of trap sites was dissimilar between trap site groupings and varied within

and between trapping periods. Thus, to standardise total horse captures, a

catch-per-unit-effort (CPUE) statistic was calculated using CPUE = G/E (Seber 1982), where

G was total horses captured and E, effort, was approximated as total trap months per trap

period. The CPUE was also an index of relative abundance (Forsyth et al. 2003; Tremblay et

al. 2009; Wiewel et al. 2009). The basic unit of effort was 1 trap month per trap site. Trap

sites with a trap paddock and steel trap yards operational at the same time (e.g. Wonga Flat)

were treated as one unit because trap paddocks were often used as holding paddocks for

horses captured in steel yards awaiting transport so the trap yard could be reset. The trap

paddock entrance was also adjacent to the trap yards and if trap yards contained a harem

group, the stallion deterred other horses. Otherwise, due to their design, trap paddocks

remained open continuously when a trap yard had been dismantled and were treated as one

unit. Trap paddocks were large fenced paddocks with a one-way funnel through which

horses can enter the paddock at any time, thus trap paddocks remained open continuously

whereas trap yards had to be cleared of horses and the trigger mechanism reset. Thus, if a

trapping period had multiple trap sites, E was calculated by summing the months that each

trap site was operational. Within a 1-month unit, the precise amount of time a trap was

open would have differed somewhat depending on the number of capture events and trap

program personnel. Despite these considerations, animal welfare criteria and a common

drive to justify contract or capture program expenditure ensured that captured horses were

removed and trap yards reset within a timeframe of days, and that lure feeding and the

checking of traps was reasonably frequent and comparable between contractors and NPWS

staff.

Captures of coacher mares and their foals were not included in horse capture

numbers. The two coacher mares on the Plateau were horses captured previously. They

were subsequently released to assist in the settling of other horses in trap yards or paddocks

as these horses were of a quiet disposition and had become semi-habituated to the presence

of humans.

Chapter 3. Indirect Effects on Macropods 59

3.2.2 Bobs Creek grazing exclusion experiment

In the Bobs Creek grazing exclusion experiment, the presence of herbivore dung was

assessed at the site and district scale. The exclosure experiment was replicated at ten sites in

Bobs Creek (Figure 3.7). At the site scale, three dung transects were marked permanently on

11–12 June 2006. Their location and orientation were chosen at random within 50 m of a

plot (Chapter 5).

Figure 3.7 Location of Bobs Creek grazing exclusion experiment exclosure sites relative to trap sites. The topography is shown using multispectral SPOT 5 imagery. The SPOT 5 image was captured on 26 May 2005; pixel resolution is 10 m (DNR 2005).

At the district scale, GIS software (ArcGIS v.9.1) was used to generate ten random

points for dung transects within a 4 × 1-km rectangular strip, 2 km either side of each site,

and 1-km wide along Bobs Creek tributary. In total, 100 dung transects were monitored in

April 2007, November 2007 and June 2008. Both site and district-scale transects were 50-

m long and dung deposits counted 5 m either side of the transect line in a quadrat of 0.05 ha.

The Paddys Plateau dung transect method was used for searching, identifying and counting

horse and kangaroo dung and clearing dung deposits.

Chapter 3. Indirect Effects on Macropods 60

Records were kept of all sightings of horses, cattle, macropods and other small

herbivores at the site scale. Details of horse and cattle mob composition and distinctive

markings of individuals were recorded and photographs taken if possible. Sites were

approached on foot stealthily and the riparian flat observed for several minutes from behind

cover for any herbivores and their location and numbers noted. Horses were commonly

encountered during area dung surveys and were not recorded as dung deposits were

deemed a more representative record of their activity. Other herbivores were rarely seen

and so a GPS location and description were taken of all sightings.

3.2.3 Landscape-scale survey of horse and non-horse catchments

A comparison of dung counts was made between two catchments occupied by

horses, Bobs Creek and Pargo Creek, and two catchments with no present or past history of

horses, Kangaroo Creek and Pantons Creek. Dung was recorded on 13 transects in each

catchment. Transects were stratified by topographic position in the landscape into hillslope

or spur, and were primarily used for landscape function analysis (LFA) in Chapter 6. While

the starting point was randomly chosen, the location of transects within the catchments

were stratified by a number of additional criteria relevant to LFA including aspect, slope and

vegetation community. As transects in horse and non-horse catchments were

environmentally equivalent (Chapter 6), the data were included in this chapter to examine

the extent of spatial separation between horses and macropods at catchment scale, that is

approximately the sum of the area of Bobs Creek and Pargo Creek (5000 ha) (Figure 6.4,

Chapter 6). Dung transects were 50 m long and dung deposits recorded 2 m either side of

the transect line in a quadrat of 0.02 ha. Dung transects were smaller than on Paddys

Plateau and in Bobs Creek due to the use of LFA gradsects as dung transects, where the focus

was on precise measurements of patch or interpatch length, width and composition, and the

ardeous terrain. At 2 m, rather than 5 m either side of the 50 m gradsect, I did not have to

deviate from the gradsect line while traversing steep slopes. Considerable time was also

spent locating environmentally equivalent gradsects, of which there were 52 in total, and

hence, 2 m was considered appropriate. The Paddys Plateau dung transect method was used

for searching, identifying and counting horse and kangaroo dung and clearing dung deposits.

Cattle dung was also counted. A single deposit corresponded to an intact cow pat. If not

explicitly stated, all dung deposits in this thesis are expressed as mean no. of deposits/ha.

Chapter 3. Indirect Effects on Macropods 61

3.2.4 Statistical analysis

3.2.4.1 Paddys Plateau district scale dung transects

At the Paddys Plateau district scale transects, the number of dung deposits (response

variable) was analysed separately for horse and macropods using a linear mixed-effects

model. Time was a fixed factor with four levels: July 2005 (T1), November 2005 (T2), March

2006 (T3), and July 2006 (T4). Habitat type (Habitat) was a fixed factor with four levels: GW

(n = 25), SW (n = 24), GS (n = 14), and T (n = 9). Transects were assigned to a Habitat after

data collection for the purpose of analysis so sample sizes were uneven. Due to the likely

variation in grazing pressure historically (possibly due to dams) and from horses during the

study as trapping effort at trap sites varied with time and with distance from Boban Hut, sites

were considered a fixed factor of interest with six corresponding levels. Site was included in

the model as exclosure site locations were used as a central reference point for stratifying

transects, although dung transects were random. As Transects were the sampling unit and

randomly selected, and Habitat had unequal sample sizes, the linear mixed-effects (lme)

function in R was appropriate. All univariate analyses in this thesis were undertaken in R

version 2.9.0 (Ihaka and Gentleman 1996). Patterns in Transect variability associated with

Site or Time were not evident in exploratory plots. A simple random effect attributed to

Transect was appropriate and converged in all analyses when the reliability of the lme

objects was checked using the intervals command in R (i.e. models were not ‘over-fitted’).

Model assumptions were checked with two diagnostic plots: (i) residuals versus fitted

responses to examine the assumption of equal variances and ensure that residuals did not

contain structure not accounted for in the model; and (ii) normal Q–Q plots to ensure the

residuals were normally distributed. Data violating these assumptions were transformed.

Horse dung counts were square-root-transformed. For macropod dung, counts were

log (X + 1)-transformed. As factors were unordered, planned post-hoc pair-wise comparisons

were made using the default Helmert contrast matrix (Venables and Ripley 2002). For single

factor linear models, the summary function in R provides pair-wise comparisons between the

baseline level and other levels. The relevel function was used to obtain comparisons

between all levels of Time.

Chapter 3. Indirect Effects on Macropods 62

3.2.4.2 Bobs Creek site scale and district scale dung transects

The response variable was the number of horse dung deposits as only horse dung

was sufficiently abundant to be analysed. To assess if the level of horse dung changed

throughout the experiment, a linear mixed-effects model was used for both the site and

district scale. The experimental design consisted of: (1) Time, a fixed factor with five (site

scale) and three (district scale) levels, and (2) Site, a random factor with ten levels. Model

assumptions were checked and pair-wise comparisons made using the same procedures as

for Paddys Plateau dung transects.

3.2.4.3 Landscape-scale survey of horse and non-horse catchments

The experimental design consisted of: (1) Treatment, a fixed factor with two levels,

horse versus non-horse; (2) Catchment, a random factor with four levels, Bobs Creek, Pargo

Creek, Kangaroo Creek and Pantons Creek; and (3) Stratum, a fixed or random factor with

two levels, hillslope versus spur. Initially, a linear mixed-effects model with Treatment and

Stratum as fixed effects and Catchment, and Stratum nested within Catchment, as random

effects was fitted. However, the interval predictions did not converge, suggesting the model

‘over-fitted’ the data. The same occurred with a simpler lme model with only Catchment as a

random effect. Therefore, the final model was a type of linear mixed-effects model called a

multistratum model (Venables and Ripley 2002 p. 285). Multistratum models occur where

there is more than one source of random variation in an experiment, as was the case for this

split-plot experiment (Heiberger 1989). The multistratum model for the landscape-scale

survey was based on Figure 3.8 (Venables and Ripley 2002 p. 282). The four Catchments

were treated as random blocks (Blocks I–IV). As only one Treatment level (e.g. horse) was

applied to each block, there were four blocks of two plots, one plot for horse and one for

non-horse (Figure 3.8). Each plot was divided into two subplots, with one level of Stratum

per subplot.

Chapter 3. Indirect Effects on Macropods 63

Figure 3.8 Split-plot design for the landscape-scale survey.

In multistratum models, the sample information and the model for the means of the

observations are partitioned into ‘strata’. To avoid confusion with the factor, Stratum, the

term ‘layer’ will be used hereafter in place of strata. The layers for the model used were:

(1) a 1-dimensional layer corresponding to the total of all observations; (2) a 3-dimensional

layer corresponding to comparisons between Treatment (or equivalent plot) totals within the

same block; and (3) a 48-dimensional layer corresponding to comparisons within plots. Such

types of models are fitted using the aov function in R, and are specified by a model formula

of the form (Venables and Ripley 2002): response ~ mean.formula + Error (layer.formula). In

this study, the response variables were the number of dung deposits for each herbivore and

the mean.formula included Treatment and Stratum. The layer.formula was Catchment,

specifying Layer 2. Layer 3 was included automatically as the ‘within’ layer. Information on

the Treatment main effect was available from Layer 2, with one degree of freedom for the

main effect and two residual degrees of freedom remaining. Information on the Stratum

main effect and the Treatment × Stratum interaction was only available from Layer 3, with

one degree of freedom each for the main effect and interaction and 46 residual degrees of

freedom. Model assumptions were checked using the same procedure as Paddys Plateau

dung transects. All herbivore dung counts were log-transformed. Post-hoc pair-wise

Chapter 3. Indirect Effects on Macropods 64

comparisons to discriminate between means for main effects were not necessary as there

were only two levels of Treatment, non-horse and horse, and two levels of Stratum, hillslope

and spur. For the interaction, planned post-hoc pair-wise comparisons were made using the

default Helmert contrast matrix (Venables and Ripley 2002).

3.2.4.4 Statistical significance defined for the thesis

Throughout this thesis a P-value ≤0.050 is considered statistically significant,

however, P-values ≤0.051–0.055 are also noted and discussed as mariginally significant and

of biological interest.

Chapter 3. Indirect Effects on Macropods 65

3.3 RESULTS

To reiterate, the number of deposits were all mean number of deposits/ha for Paddys

Plateau, Bobs Creek and the landscape-scale survey in horse and non-horse catchments in

Section 3.3.

3.3.1 Paddys Plateau district scale dung transects

3.3.1.1 Horse dung and habitat types

Horse dung deposits peaked across all habitat types in July 2005 (T1) and

subsequently declined to varying extents across habitat types, the Habitat × Time interaction

being significant (F9,144 = 3.14, P = 0.002; Table 3.3, Figure 3.9).

Horse dung declined in all habitat types between T1 and T2 with large proportional

reductions (%) in dung counts in most habitat types: GW (80.2%, P < 0.001), GS (59.5%,

P < 0.001), SW (50.2%, P < 0.001) and T (37.7%, P = 0.016) (Figure 3.9). Horse dung was less

in T2–T4 than T1 in all habitat types (P < 0.050). Dung changed little in GW and SW between

T2 and T4 but progressively declined in GS and T from T1> T2 > T3 = T4 in dung counts. The

additional 50.0% and 54.1% reductions in dung deposits in GS and T, respectively, between

T2 and T3 was significant for track (P = 0.050) and almost significant for grassy swale

(P = 0.076) (Figure 3.9). In both winter sampling times (T1 and T4), deposits were

significantly less in SW than all other habitat types (P < 0.050) except track in T4 when the

significance level was mariginal (P = 0.054), whereas in summer (T2) and early autumn (T3)

deposits were significantly greater in T than GW and SW (P ≤ 0.048). In summer, GS was

intermediate to T and the other habitat types, differing from GW (P = 0.002).

Chapter 3. Indirect Effects on Macropods 66

Figure 3.9 Mean (±1 S.E.) number of horse deposits/ha by Time and Habitat. Accumulation periods were July 2005 (T1), November 2005 (T2), March 2006 (T3), and July 2006 (T4) for the Habitat types grassy woodland (GW), shrubby woodland (SW), grassy swale (GS) and track (T). The text notation above the set of four bar columns for an accumulation period denotes significant differences between habitat types specific to that period (P ≤ 0.050). Significant differences between periods only refer to bar columns with an asterisk above the habitat type (P ≤ 0.050).

Table 3.3 Multifactor linear mixed-effects model output for horse and macropod dung deposits on dung transects. Numerator (Num) and denominator (Den) degrees of freedom (df).

Horse Macropod Source of variation Num df Den df F P F P Habitat 3 48 8.34 <0.001 5.37 0.003 Site 5 48 4.20 0.003 10.26 <0.001 Time 3 144 86.17 <0.001 31.08 <0.001 Habitat × Site 15 48 0.48 0.940 1.30 0.237 Habitat × Time 9 144 3.86 0.001 2.36 0.016 Site × Time 15 144 2.92 0.001 3.41 <0.001 Habitat × Site × Time 45 144 1.35 0.093 1.21 0.204

3.3.1.2 Macropod dung and habitat types

Over 90% of macropod dung was easily identified as eastern grey kangaroo. In

July 2005, macropod dung was rare and only recorded in SW and GS at an average of

≤7.5 deposits (Figure 3.10). After T2, macropod dung progressively increased across all

habitat types, moreso in GS, followed by GW and T. The Habitat × Time interaction was

significant (F9,144 = 2.36, P = 0.016; Table 3.3) with macropod dung greater in T2–T4 than T1 in

0

50

100

150

200

250

300

350

400

Hor

se d

epos

its

(no.

/ha)

GW SW GS T

*

*

T1 > T2, T3, T4 *

T3 < T2

July 2005 November 2005 March 2006 July 2006

GW, GS, T > SW

* *

T4 < T2

T > GW, SW

*

T > GW, SWGS > GW

GW, GS > SW

Chapter 3. Indirect Effects on Macropods 67

GW and GS (P ≤ 0.005). Incremental increases between T2 and T3 and between T3 and T4

were significant for GS (P ≤ 0.024) and for GW and SW between T3 and T4 only (P ≤ 0.013).

The increase in macropod dung in track between T3 and T4 differed from T1 (P = 0.005).

Habitat type differences were consistent, with greater macropod dung in GS than SW and T

at T2–T4 (P ≤ 0.048) and GW intermediate and greater than SW at T3 and T4 (P ≤ 0.042).

Figure 3.10 Mean (±1 S.E.) number of macropod deposits/ha by Time and Habitat. Notation as for Figure 3.9 except for July 2006 within habitat type time differences, where the notation directly above the track bar graph referred to track only and the notation spanning the first three bars referred to GW, GS and SW. 3.3.1.3 Horse dung and site differences

In July 2005, transects had an average of ≥161.7 horse deposits across all sites. The

Site × Time interaction was significant (F15,144 = 2.92, P = 0.001; Table 3.3) as horse dung

declined in sites at different times through the course of the experiment (Figure 3.11). Dung

temporarily declined in Site 5 between T2 and T3, differing from counts at T1 and T2

(P < 0.001). Otherwise, sampling times did not differ and dung was greater in Site 5 than all

other sites at T2 and T4. Conversely, dung deposits ‘crashed’ to a mean of ≤50.0 deposits in

Sites 1–4 and Site 6 sometime after T1 (Figure 3.11). The response was immediate in Site 1

and Site 2 and occurred between T1 and T2 (P < 0.001), whereas declines were progressive in

Sites 3, 4 and 6. Dung declined to ≤50.0 deposits in Site 3 between T2 and T3 (P < 0.001) and

0

20

40

60

80

100

120

140

160

180

200

Mac

ropo

d de

posi

ts (

no./

ha)

GW SW GS T

*

T1 < T2, T3, T4

*

*GS > GW, SW, TGW > SW

GS > SW, TGW > SW

July 2005 November 2005 March 2006 July 2006

*

*

T3 > T2

*

GS > SW, T

T4 > T3

*T4 > T1

Chapter 3. Indirect Effects on Macropods 68

Sites 4 and 6 between T3 and T4. Horse dung was less at T2–T4 than T1 in all sites except

Site 5 (P ≤ 0.001).

Figure 3.11 Mean (±1 S.E.) number of horse deposits/ha by Time and Site. Times: July 2005 (T1), November 2005 (T2), March 2006 (T3) and July 2006 (T4), Sites: Site 1 (S1)–Site 6 (S6). The text notation above the set of six bar columns for an accumulation period denotes significant differences between sites specific to that period (P < 0.050). Significant differences between periods expressed in the text notation only applys to sites with an asterisk above the bar column (P < 0.050).

3.3.1.4 Macropod dung and site differences

The Site × Time interaction was significant (F15,144 = 3.41, P < 0.001; Table 3.3) as

macropod dung increased in sites at different times through the course of the experiment

(Figure 3.12). In July 2005 (T1), macropod dung was only recorded in Site 1 (a total of

11 deposits across three transects). In November 2005 (T2), macropod dung was recorded

in Sites 1–4 with an average of 1.7–23.3 deposits across sites. Dung increased to 116.7 and

53.3 deposits, respectively, in Site 1 (P < 0.001) and Site 2 (P = 0.050) during the March 2006

accumulation period, and to 181.7 (P = 0.042) and 83.3 deposits, respectively, in July 2006.

Dung was significantly greater in Site 1 than other sites by 64.2–116.8 deposits in

March 2006 and July 2006 (P < 0.050).

Dung only significantly increased in Site 3 (to a mean of 60.0 deposits) and Site 4 (to a

mean of 110 deposits) during the July 2006 accumulation period (P < 0.050). In July 2006,

dung was also greater in Sites 2–4 than Site 5 and Site 6. No macropod dung was recorded in

0

50

100

150

200

250

300

350H

orse

dep

osit

s (n

o./h

a)

1 2 3 4 5 6

July 2005 November 2005 March 2006 July 2006

*

S5 > S(1, 2, 3, 4, 6)

S5 > S(1, 2, 3, 4, 6)*

*

*

*

T1 > T2, T3, T4

*

T2 > T3

*

T3 < T1, T2

Chapter 3. Indirect Effects on Macropods 69

Site 5 and Site 6 until July 2006 when the total of a single deposit of kangaroo dung was

found in Site 5 and a total of 6 deposits across two transects in Site 6.

Figure 3.12 Mean (±1 S.E.) number of macropod deposits/ha for Time by Site. Notation as for Figure 3.11.

3.3.2 Horse capture and removal data for Paddys Plateau

The NSW NPWS trapping program results were summarised to show when trap sites

were operational and the number of horses trapped (Table 3.4). The term ‘trapped’ refers to

the capture and removal of horses from the Park. Months not shown were when the

program was halted and no trap sites were operational. Opportunistic lure feeding by NSW

NPWS field staff continued throughout. A trap month was when a site was operational, that

is, the trap contained feed and was set to capture horses. Alternatively, the trap held

trapped horses waiting to be transferred to a holding paddock or transported off-park, after

which the trap was re-set.

The number of horses trapped was greater in the first 2 trap months of each year of

the program, or the first 2 trap months that a trap site was in operation in any given year

(Table 3.4). In 2004, 113 horses were trapped over 13 trap months. In 2005 and 2006, the

number of horses trapped per year declined despite an increase in trap months to 21 months

and 17 months.

0

50

100

150

200

250

300M

acro

pod

depo

sits

(no

./ha

)1 2 3 4 5 6

July 2005 November 2005 March 2006 July 2006

S1 > S(2, 3, 4, 5, 6)

S1 > S(2, 3, 4, 5, 6)S2, S3, S4 > S5, S6

*T3 > T1, T2

*T3 > T1

*T4 > T(1, 2, 3)

*

T4 > T1, T2

*T4 > T(1, 2, 3)

*

T4 > T1, T2

Chapter 3. Indirect Effects on Macropods 70

Table 3.4 Number of horses trapped on Paddys Plateau in each trap month and year of the trapping program. TY: Trap yard, TP: Trap Paddock, LF: Lure feeding only; '–' indicated a trap site was ‘closed’ whereas a 0 referred to no horse captures in an operational trap yard or paddock. Total numbers of horse captures for each year are italicised.

2004 Trap area April May July August September November Area totals Wonga Flat (TY, TP) 29 13 3 1 2 4 52 Perrys Yards (TY) 1 0 5 5 1 - 12 Boban Hut (TY, TP) - - LF LF 10 39 49 Monthly Totals 30 13 8 6 13 43 113

2005

Trap area May June September October November December Area totals

Wonga Flat (TY, TP) 5 12 0 3 3 0 23 Perrys Yards (TY) 4 0 0 1 1 1 7 Ryans Paddock (TP) - - LF LF 5 0 5 Boban Hut (TY, TP) 8 16 2 3 9 - 38 Spion Kiope (TY) - LF LF 2 1 - 3 Monthly Totals 17 28 2 9 19 1 76

2006

Trap area April June August September October November Area totals

Wonga Flat (TP) 0 1 0 0 - - 1 Mt Gardiner Plateau (TY) 10 0 - - - - 10 Perrys Yards (TY) LF 1 0 - - - 1 Ryans Paddock (TP) LF LF 4 0 - - 4 Middle Dam (TY, TP) 6 0 3 0 TP only TP only 9 Boban Hut (TY, TP) - LF LF 12 7 8 27 Monthly Totals 16 2 7 12 7 8 52

2007 Trap area February March Area totals Ryans Paddock (TP) 0 2 2 Boban Hut (TY, TP) 6 8 14 Monthly Totals 6 10 16

Chapter 3. Indirect Effects on Macropods 71

3.3.2.1 Trap sites 1–3

CPUE values tended to decline as the trap programs progressed in time, with the first

two trap periods (T1–T2) capturing most horses (6.00 and 5.25 horses/month), respectively

(Table 3.5). After November 2005 (T2), horse captures were low (≤1.71 horses/month)

except in July 2006 (T4). In the July 2006 trap period, almost all (16) of the 18 horses were

captured in April 2006 (Table 3.4). This was the first month that the trapping program

resumed in 2006 after the 3-month summer break, with lure feeding commencing in

February 2006. Capture comments for most horses caught during T1 and T2 mentioned

prior sightings or that the horses were known on Paddys Plateau, but the April 2006 captures

appeared to be recent immigrants. A mob of ten horses was captured at Mt Gardiner

Plateau trap site and after no horses were captured in the following trap month, the trap site

was closed (Table 3.4). It was not re-opened for the duration of this study as there was no

further build-up of mobs in the Mt Gardiner and Wonga Flat region. The other trap site was

Middle Dam, and as trapping in subsequent months caught few horses the trap yards were

permanently closed (Table 3.4). While the trap paddock remained open for a further

2 months, no horses were captured (Table 3.5). The increase in the CPUE to

2.57 horses/month in July 2006 was due to the Mt Gardiner and Middle Dam captures in

April 2006 and few horses were captured in the remaining 5 trap months in 2006. The CPUE

of 0.78 horses/month for the Post-July 2006 trap period was low compared to the first three

trap periods (Table 3.5).

Table 3.5 Summary of trap data from the NSW NPWS capture and removal programs. No. of trap sites included trap sites in operation for at least 1 trap month. CPUE: catch-per-unit-effort, No.: number. '—' indicated trap site closed.

Total No. of Total trap CPUE Trapping period horses trap sites months TRAP SITES 1–3 Pre-July 2005 60 2 10 6.00 July 2005 (T1) 21 2 4 5.25 November 2005 (T2) 12 2 to 3 7 1.71 March 2006 (T3) 1 3 3 0.00 July 2006 (T4) 18 3 to 4 7 2.57 Post-July 2006 7 1 to 4 9 0.78 TRAP SITES 4–6 Pre-July 2005 10 1 1 10.00 July 2005 (T1) 23 1 2 11.50 November 2005 (T2) 18 1 to 2 5 3.60 March 2006 (T3) — — — — July 2006 (T4) — — — — Post-July 2006 27 1 3 9.00

Chapter 3. Indirect Effects on Macropods 72

3.3.2.2 Trap sites 4–6

CPUE values tended to fluctuate according to the intensity of the preceding trap

period (Table 3.5). Additional factors were immigration, the late start of the capture

program at Boban Hut and Spion Kiope, the smaller number of trap sites, and the greater

frequency of trap closures, and the continuation of the program at Boban Hut in 2006 and

2007 after all but one trap site had been permanently closed at trap sites 1–3 by

September 2006 (Table 3.4).

The Pre-July 2005 capture period encompassed only the first trap month,

September 2004, at Boban Hut (Table 3.5), when ten horses were captured (Table 3.4). The

CPUE for the subsequent trap period, July 2005 (T1), was 11.50 horses/month (Table 3.5).

The pattern for trap sites 1–3 was repeated at trap sites 4–6 in that the CPUE was

comparatively low (3.60 horses/month) in the November 2005 (T2) trap period compared to

the previous two trap periods, although 2.2 times greater than the corresponding CPUE for

trap sites 1–3. Trap sites 4–6 were closed for the March 2006 (T3) and July 2006 (T4) trap

periods. This may explain the Post-July 2006 value of 9.00 horses/month.

3.3.3 Bobs Creek site scale and district scale dung transects

3.3.3.1 Dung transects

Only horse dung was recorded on dung transects at the site scale (Figure 3.13a) with

an average of approximately 158.7–241.3 deposits across the five sampling times. The Time

main effect was marginally significant (F4,136 = 2.39, P = 0.054). Pair-wise comparisons were

only significant between the first sampling time (241.3 deposits), when the accumulation

period was undefined, and November 2007 (170.7 deposits, P = 0.018) and June 2008

(158.7 deposits, P = 0.006).

District-wide, judging by their dung, horses were the most consistent and abundant

mammalian herbivore within a 4 × 1-km area of sites, whereas cattle and macropods were

rare (Figure 3.13b). To illustrate, in April 2007, 96% of transects recorded horse dung, while

only 2% (2 transects) recorded one macropod dung deposit per transect and the transect

where the mob of four cattle was sighted contained six cattle deposits. Thus, overall,

1033 horse deposits were recorded compared to two macropod and six cattle deposits in

that month. In November 2007 and June 2008, 91% and 87% of transects had horse dung

whereas no macropod or cattle dung was recorded. The Time main effect was significant

(F2,288 = 8.84, P < 0.001). The mean number of horse deposits was significantly lower in

Chapter 3. Indirect Effects on Macropods 73

November 2007 (P = 0.001) and June 2008 (P = 0.002) than April 2007, as dung had

accumulated over an undefined period at the first sampling time and at the second and final

sampling times the accumulation period was limited to 8 and 9 months respectively. Horse

dung abundance did not differ between the two defined accumulation periods (P = 0.386).

Figure 3.13 Mean (±1 S.E.) number of horse deposits/ha recorded from (a) 30 dung transects at the site scale for horses only, where * denotes a significant difference (P < 0.050) between Time 1 (T1, June 2006) and both Time 3 (T3, November 2007) and Time 5 (T5, June 2008) and (b) 100 transects at the district scale for the three herbivores, where * denotes a significant difference (P < 0.050) between Time 1 (T1, April 2007) and both Time 2 (T2, November 2007) and Time 3 (T3, June 2008).

3.3.3.2 Herbivore sightings

Sightings were consistent with site scale dung transects as horses were the only large

herbivores observed grazing the flats (Table 3.6). At least one horse or horse mob was seen

on all but 1 day during the first two sampling times, and then every day for the remaining

three sampling times. Some mobs were seen repeatedly. Multiple sightings of horses were

recorded at each site and the number of horses ranged from a single individual to 12 adults

and four juveniles, which appeared to be three separate mobs grazing together. Otherwise,

just the one brown hare and no cattle or macropods were observed in sites (Table 3.6). A

mob of four cattle was observed on 17 April 2007. However, the mob was 3 km downstream

of Site 1 beyond the study area (site numbers progressed upstream).

0

50

100

150

200

250

300

Ho

rse

de

po

sits

(n

o./

ha)

Apr-07 Nov-07 Feb-08 Jun-08Jun-06

a)

*

T1 > T3, T5

0

50

100

150

200

250

April 2007 November 2007

June 2008

Dun

g de

posi

ts (

no./

ha)

HorseMacropodCattle

b)

*

T1 > T2, T3

Chapter 3. Indirect Effects on Macropods 74

Table 3.6 Herbivore sightings at riparian exclosure sites. ‘Visitation days’ were the number of days that the riparian exclosures were monitored. Sighting events were the number of times that horses were observed grazing control plots or sites.

Jun-06 Apr-07 Nov-07 Feb-08 Jun-08

No. of visitation days 6 7 7 6 7 No. of horse sighting events 5 6 9 6 7 Sighting events/visitation days 0.83 0.86 1.29 1.00 1.00 No. of horses seen 24 26 31 34 25 No. of cattle seen 0 0 0 0 0 No. of macropods seen 0 0 0 0 0 No. of rabbits/hares seen 0 0 1 0 0

3.3.3.3 Horse capture and removal data

Ballards Flat was the only trap site operational in 2006, and a total of 29 horses were

captured in 4 months in 2006 and 45 horses in 2007 (Table 3.7). Deep Water trap site was

first operational in June 2007 when seven horses were captured. In 2008, Ballards Flat and

Deep Water were operational in February and April, with respective totals of ten and

12 horses in those 2 months. Deep Hole and Pargo were operational in May and June 2008

with a total of eight horses captured at each trap site.

Table 3.7 Total number of horses trapped at four trap sites in or adjacent to Bobs Creek catchment during 2006–2008. And '–' indicates that the trap site was closed.

2006 2007 2008 May, June, February, March, February, April,

Trap yard site September and October June and July May and June Ballards Flat 29 45 10 Deep Water – 7 12 Deep Hole – – 8 Pargo – – 8 Yearly totals 29 52 38 Horses in total 119

3.3.4 Landscape-scale survey of horse and non-horse catchments

3.3.4.1 Horse dung

In horse catchments (Bobs and Pargo Creek), horse deposits were recorded on all

26 dung transects, and the presence of horses confirmed by frequent sightings and other

indirect signs such as hoof prints. Horse dung averaged 532.7 ± 71.7 deposits and the

amount of horse dung on slopes and spurs did not differ as the Stratum main effect was not

significant (F1,46 = 0.32, P = 0.570; Table 3.8, Figure 3.14a). In non-horse catchments

Chapter 3. Indirect Effects on Macropods 75

(Kangaroo and Pantons Creek), no horse deposits were recorded on transects, nor were any

signs of horses observed. Hence, the difference in mean dung deposit counts between horse

and non-horse catchments and the Treatment main effect was highly significant (F1,2 = 2138,

P < 0.001; Table 3.8).

3.3.4.2 Macropod dung

The opposite trend was recorded for macropod dung. Only a single dung deposit was

recorded on three transects in horse catchments, whereas single to multiple macropod dung

deposits were recorded at all 26 transects in non-horse catchments. The mean number of

macropod dung deposits in non-horse catchments (551.9 ± 92.1 deposits) was 91% greater

than in horse catchments (48.1 ± 16.8 deposits). The Treatment × Stratum interaction was

significant (F1,46 = 11.58, P = 0.001; Table 3.8) because in horse catchments, macropod dung

deposits were more abundant on spurs than hillslopes, whereas in non-horse catchments

there was more macropod dung on hillslopes than spurs (Figure 3.14b).

Figure 3.14 Mean (±1 S.E.) number of deposits/ha of (a) horse and (b) macropod dung on hillslopes and spurs in horse and non-horse catchments. Table 3.8 Multifactor ANOVA corresponding to the mean (±1 S.E.) number of herbivore dung deposits/ha on hillslopes and spurs in horse and non-horse catchments. Mac.: Macropod, Treat.:Treatment.

Horse catchments Non-horse catchments Source of variation (P-values) Treatment

Slope Spur Slope Spur Treat. Stratum × Stratum Horse 539.3 ± 125.6 525.0 ± 59.5 0.0 ± 0.0 0.0 ± 0.0 0.000 0.570 0.570 Mac. 10.7 ± 5.7 91.7 ± 31.8 582.1 ± 110.1 516.7 ± 157.6 0.160 0.570 0.001 Cattle 0.0 ± 0.0 0.0 ± 0.0 14.3 ± 11.0 125.0 ± 55.2 0.007 0.049 0.049

0

200

400

600

800

1000

Bobs Pargo Kangaroo Pantons

Hor

se d

epos

its

(no.

/ha)

Slope

Spur

Horse Non-horse

a)

0

200

400

600

800

1000

1200

Bobs Kangaroo

Mac

ropo

d de

posi

ts (

no./

ha)

Slope

Spur

Horse Non-horse

b)

Pargo Pantons

Chapter 3. Indirect Effects on Macropods 76

3.3.4.3 Cattle dung Cattle dung was present on seven of the 26 transects in non-horse catchments with

an average of 65.4 ± 27.8 dung deposits, whereas there was no cattle dung in horse

catchments (Figure 3.15). The Treatment × Stratum interaction was significant

(F1,46 = 4.08, P = 0.049; Table 3.8), with the majority of cattle dung recorded on spurs and

little dung on hillslopes in non-horse catchments.

Figure 3.15 Mean (±1 S.E.) number of cattle dung deposits/ha on hillslopes and spurs in horse and non-horse catchments.

0

40

80

120

160

200

Bobs Pargo Kangaroo Pantons

Catt

le d

epos

its

(no.

/ha)

Slope

Spur

Horse Non-horse

Chapter 3. Indirect Effects on Macropods 77

3.4 DISCUSSION

The Paddys Plateau dung transects indicated that horses displaced macropods and

probably deterred them from utilising forage resources at the district scale (100 ha). At four

of the six sites, as horse deposits declined, the number of macropod deposits increased until

macropod dung was more prevalent than horse dung. Importantly, the trend was staggered

across sites depending on their relative proximity to trap locations and how quickly, and to

what level, horse dung declined. Trends in catch-per-unit-effort (CPUE) values reinforced

patterns in dung transect counts and supported the argument that macropods were

responding to changes in the abundance of horses, rather than the removal of horses simply

coinciding with an increase in macropod numbers or activity.

When dung transects were established in July 2005 (T1) peak levels of horse dung in

all sites did not differ whereas macropod dung was rare and restricted to Site 1 (total of

11 deposits across all transects). The CPUE of 5.25 horses/month calculated for trap sites 1–

3 over the 4 months prior to July 2005 was not much lower than the 6.00 horses/month

estimated for the first 6 months of the trapping program, suggesting peak horse deposits in

July 2005 reflected a high abundance of horses rather than over-estimation due to the

unrestricted accumulation period. After July 2005, horse dung consistently declined in all

sites except Site 5. The response was abrupt in Sites 1 and 2, with mean deposits decreasing

by 88.0% and 82.1%, respectively, to ≤33.3 deposits/ha between July 2005 (T1) and

November 2005 (T2). Over the same period, CPUE values at both trap sites 1–3 and 4–6

declined by two-thirds and macropod dung increased at Sites 1–4 to an average

of 23.3 deposits/ha or less. The summary of demographic data in the trapping program

(Appendix 3) suggested that the presence of horse dung in Sites 1 and 2 was a result of

transitory rather than long-term resident horse activity, and associated horse dung levels of

≤40.0 deposits/ha were termed ‘nominal’ dung levels to reflect demographic data. Over the

subsequent accumulation period (between T2 and T3), trap sites 1–3 were in operation for

3 trap months but no horses were trapped. In the absence of horses, macropod dung

increased by 80.1% in Site 1 and 75.4% in Site 2 so that macropod dung was more prevalent

than horse dung by 86.3 and 34.7 deposits/ha, respectively. The pattern in Sites 1 and 2 of

horse dung declining to nominal levels and macropod dung increasing over the following

accumulation period and continuing to increase was progressively repeated, first at Site 3,

then Sites 4 and 6. CPUE values for trap sites 1–3 also remained low during the course of the

experiment. After June 2005, zero or one horse was captured per month in most trap

Chapter 3. Indirect Effects on Macropods 78

months and trap sites associated with sites 1–3 (e.g. Wonga Flat and Perrys Yard) prompting

the permanent closure of trap sites 1–3 after June 2006. CPUE values for trap sites 4–6

were consistently at least twice that at trap sites 1–3 and while not in operation during the

last two dung accumulation periods, the Post-July 2006 CPUE (9.0 horses/month) was almost

as high as the first two capture periods. The CPUE for trap sites 1–3 (0.78 horses/month) was

low at this time. This difference may explain why horse dung decreased at Sites 3, 4 and 6

later than in Sites 1 and 2, which were closest to trap sites 1–3, and the greater number of

horse deposits in Site 5 (mean of 112.0 deposits/ha), adjacent to the primary trap site, Boban

Hut, at the final accumulation period (July 2006). As a result, only one macropod dung

deposit was ever detected on Site 5 transects. Patterns for horse dung at Site 6 resembled

Site 4 in that horse dung was low (50.0 deposits/ha) by the final accumulation period, but

macropod dung did not increase. The proximity of Site 6 to Boban Hut may have continued

to deter macropods. Site 4 exclosures were closer to Boban Hut than the Site 6 exclosures,

but Site 4 dung transects were located south towards the Combolo catchment border. Dung

transects in Sites 5 and 6 were located north of exclosures and adjacent to the Bobs Creek

catchment ridgeline that served as a movement route from the Sara River flats. Therefore,

by the final accumulation period horse dung had declined in Sites 1–4 from 161.7–

255.0 deposits/ha in July 2005 to ≤40.0 deposits/ha, whereas macropod dung had

significantly increased from almost nothing to 60.0–181.7 deposits/ha in response to the low

abundance of horses.

The inverse relationship between horse and macropod dung was strongest in habitat

types thought to be prime grazing areas for both herbivores. The majority of macropod dung

detected in March 2006 was in grassy swales and grassy woodlands. In the final

accumulation period, macropod dung was greatest in grassy swales (134.3 deposits/ha)

followed by grassy woodlands (88.0 deposits/ha), and although both habitats registered

more dung than shrubby woodland, only grassy swale differed from track. The order of

habitat types from greatest to least number of dung deposits for macropods in March and

July 2006 mirrored that for horses in July 2005, confirming a high degree of overlap in habitat

preferences between the species. In the final accumulation period macropod deposits in

shrubby woodland also increased by 71.0%, accompanied by a substantial increase in track

transects (63.6%). Macropods appeared to expand their use of Paddys Plateau over time as

progressively more horses were removed and, by the final accumulation period, macropod

dung was also significantly greater in more marginal habitat types. Given the result for

Chapter 3. Indirect Effects on Macropods 79

grassy swales, in particular, the relative difference in the proportion of transects in grassy

swales may partly explain why the response of macropods was greater in Site 1 (0.25) than

Site 2 (0.17) and in Site 4 (0.25) than Site 3 (0.08). In addition, while Site 1 had significantly

more macropod dung than other sites in March and July 2006, it was also the only site to

have some macropod dung during the first accumulation period. Macropods were well

established in the south-eastern section of Paddys Plateau near Mt Wonga and Tallagandra

Depot. This area of the Park either borders large grazing properties or contains small parcels

of fenced paddocks privately owned or leased which are used for grazing cattle. Hence, the

rapid colonisation of areas by macropods once horses were no longer present was not

surprising.

The pattern on Paddys Plateau was not repeated in Bobs Creek. The horse dung

counts and the trapping data suggested that this was because, unlike the Plateau, the

relative abundance of horses in Bobs Creek did not decline during the study. No macropod

dung was recorded at the site scale (0.01 ha) and just two deposits in total were recorded

district-wide (4 × 1 km), compared to an average of at least 160.0 horse deposits/ha at both

scales. Except for the baseline horse dung counts when the accumulation period was

potentially as long as the time to decay, mean horse deposits at the site and district scale did

not decline significantly through time. Horses were consistently sighted in similar frequency

and numbers grazing the Bobs Creek riparian flats and while monitoring regional dung

transects. The density of horses is thought to be greatest in Bobs Creek, followed by Pargo

Creek and the Sara River (Chapter 2). Yet in the first year of trapping on Paddys Plateau,

almost the same number of horses were trapped (113 horses in 2004) as the total number of

horses trapped along the Sara River in 2 years (119 horses). If the NPWS continue to remove

horses and in numbers greater than the annual population growth rate, it may take longer

for macropods to colonise Bobs Creek than Paddys Plateau since Bobs Creek is not

surrounded by a reserve population of macropods sustained by pastoral lands. The absence

of macropod dung was not due to lack of suitable habitat for macropods. At least five

species of macropod have been sighted historically in the Sara River, Bobs Creek and Pargo

Creek catchments (NSW NPWS 2009a), and macropods were observed in unprecedented

numbers after the October 2000 cull on the Sara River flats (Olsen and Low 2006). The

presence of macropod dung on all transects in non-horse catchments (Kangaroo and Pantons

Creek), with an average of 551.9 ± 92.1 deposits/ha would appear to support that

assessment, as the locations of transects were environmentally matched with those in horse

Chapter 3. Indirect Effects on Macropods 80

catchments (Bobs and Pargo Creek). Consistent with the Bobs Creek exclosure transects, just

the single macropod deposit was recorded on three individual transects of the 12 transects in

Bobs Creek catchment. Levels of macropod dung were low in Pargo Creek in comparison to

non-horse catchments, but more prevalent than in Bobs Creek, ranging from 1.0–7.0 deposits

per transect across eight transects. Fewer horses have historically been recorded from aerial

surveys in Pargo Creek compared to Bobs Creek (Chapter 2). Pargo Creek thus drove the

response of macropods in horse catchments, where macropods appeared to change their use

of hillslopes and spurs in the presence of horses. In non-horse catchments, macropod dung

tended to occur more on hillslopes than spurs, while the opposite was true in horse

catchments. The lack of dung on hillslopes in horse catchments suggests that macropods do

not forage in horse catchments, and perhaps only use spurs occasionally when travelling

through. GFRNP is considered a control comparison for wild dog control programs in other

national parks in the region (e.g. Oxley Wild Rivers National Park, Guy Ballard, I&I

pers. comm.) as the wild dog population is not controlled or managed in any area of the Park

(S. Leathers pers. comm.). Thus, wild dog control would not have influenced macropod or

horse distribution throughout this study.

What remains unknown is the mechanism underlying the evident dissociation

between horses and macropods, both at the smaller site scale and broader catchment scale.

Fankhauser et al. (2008) questioned a perceived propensity to explain the segregation of

livestock and native herbivores as exploitative competition (e.g. Newsome 1971; Caughley

1987; Wilson 1991b) without also considering ultimate reasons, such as the need for native

species to avoid transmission of disease or gastrointestinal parasites via dung. A possible

exception is Andrew and Lange (1986), who suggested kangaroos and sheep dissociated in

their study because kangaroos selected pastures that were ungrazed by sheep or because

sheep disturbed sites had become fouled in some way (e.g. excessive dung). Eastern grey

kangaroos have been found to avoid the dung of conspecifics by moving through patches

contaminated with gastrointestinal parasite larvae as encountered, remaining longer in

uncontaminated patches, rather than actively selecting less contaminated patches (Garnick

et al. 2009). This response was consistent with that of Ramp and Coulson (2002, 2004), who

found that eastern grey kangaroos made foraging decisions at the habitat scale, with no

evidence of patch choice. The eastern grey kangaroos in Garnick et al. (2009) were unable to

discriminate between parasite-infected and parasite-free dung and did not adjust their

foraging behaviour in response to variation in the density of parasite larvae. Thus, they

Chapter 3. Indirect Effects on Macropods 81

evaded contaminated patches in general to avoid contacting larvae, as 95% of larvae is often

found <1 m of domestic horse and other ungulate dung (Sykes 1987; Fleurance et al. 2005;

Fleurance et al. 2007). As the main argument for dung avoidance is that it reduces exposure

to gastrointestinal parasite larvae (e.g. nematodes), for dung avoidance to apply to this

study, horses and eastern grey kangaroos on Paddys Plateau should be infected by some of

the same species of intestinal parasites (Sarah Garnick, pers. comm.), which is unknown at

this stage. Interspecific dung avoidance has rarely been addressed and is not well

understood (Benham and Broom 1991; Aoyama et al. 1994; Daniels et al. 2001; Fankhauser

et al. 2008) and cannot be immediately ruled out as a mechanism of avoidance on Paddys

Plateau. However, given the limited evidence available at this stage, an initial analysis of the

degree of overlap in parasite species between horse and eastern grey kangaroo dung is

essential before a manipulative behavioural and field experiment is considered.

Exploitative or interference competition was equally plausible. Overlap in habitat

preferences and diet was evident in dung counts and biomass results (Chapter 4), but

preferences and feeding strategies are also important in exploitative competition. In

environments most compatible with GFRNP, horses have the same feeding strategy as

eastern grey kangaroos in Australia’s temperate grasslands (Chapter 1). Both species are

true grazers feeding predominantly on grasses and respond to quality over quantity by

selectively spending more time feeding in areas with a greater density of green plant tissue

(Salter and Hudson 1979; Hill 1982; Duncan 1983; Taylor 1984; Duncan 1992; Crane et al.

1997a; Linklater et al. 2000). In addition, unlike cattle who lack top incisors, horses have

both top and bottom incisors and a more elongate head and flexible lips (Rook et al. 2004).

This enables them to trim vegetation close to the ground and then regraze the high quality

soft, short green shoots when they sprout from the crown (Menard et al. 2002; Lamoot et al.

2005). Horses feed on grass too short for cattle in at least two European grazing systems

(Gordon 1989). Thus, both horses and eastern greys exhibit a preference for and ability to

utilise short swards or grazing lawns based on nutritional value (Hill 1982; Rogers 1991;

Landsberg and Stol 1996). This would explain the apparent contradiction with studies where

eastern grey kangaroos selectively foraged closer to cattle in their near (<100 m) and broad

distributions (Hill 1982; Payne and Jarman 1999; Ritchie et al. 2009) to access the higher

quality ‘green pick’ exposed when cattle reduce the biomass of dry, perennial grasses (Frith

1970; Newsome 1971, 1975).

Chapter 3. Indirect Effects on Macropods 82

While overlap in resource use highlights the possibility for competition, interspecific

competition can only occur if resources are limiting to at least one of the species with

resultant demographic consequences for one or both species (Schoener 1983; Wiens 1989;

Putman 1996). On Paddys Plateau, grassy swale and grassy woodland habitats were

common and well dispersed, and biomass did not appear to be limiting (Chapter 4) even

when horses were relatively abundant. When macropod dung was still rare on dung

transects at June and December 2005, biomass in exclosures was above 100 g/m2 across all

sites. In determining the functional response of red kangaroos (Macropus rufus) in the semi-

arid zone, Short (1985) predicted the species only became food limited at a vegetation

biomass of 25–30 g/m2. Manipulative field experiments have concurred with this prediction.

Exploitative competition between large kangaroos and domestic sheep first became

apparent at a total pasture biomass of 40–50 g/m2 or in comparative dry years (Andrew and

Lange 1986; Wilson 1991a, 1991b; Norbury and Norbury 1993; Edwards et al. 1996),

although the evidence for exploitative competition was equivocal (Squires 1982; Edwards

1989; Payne and Jarman 1999 for a review). Short’s model has also been applied to

interactions between eastern grey kangaroos and other native wildlife, and an average

biomass of more than 100 g/m2 was considered sufficient to rule out exploitative

competition (Woolnough and Johnson 2000). On that basis, the potential for exploitative

competition would be greater for the riparian flats along Bobs Creek tributary considering

biomass in spring was as low as 45 g/m2 (Chapter 5) and the flats are small in size and rare in

the catchment. Fletcher (2006) recently examined the functional response of eastern grey

kangaroos in temperate kangaroo grass-dominated grasslands. A number of functional

responses were plausible, including Short’s model for red kangaroos, however, there was

also evidence of satiation of eastern grey kangaroos requiring high herbage mass

(>600 g/m2), which should be investigated further before exploitative competition is

dismissed for Paddys Plateau.

The final explanation presumes the existence of a social dominance hierarchy where

as subordinates, macropods altered their foraging behaviour in response to the direct

presence or threat of horses (Van Kreveld 1970; Beilharz and Zeeb 1982; Drews 1993).

Dominance hierarchies may be intrinsically determined (French and Smith 2005), but

generally arise out of interference competition (Fellers 1987; Savolainen and Vepsalainen

1989), where body size and mass or relative number of individuals determine interspecific

rank (Fisler 1977; Shelley et al. 2004). Mob size and dynamics of horses and eastern grey

Chapter 3. Indirect Effects on Macropods 83

kangaroos are comparable (Kaufmann 1975; Taylor 1982; Jarman and Coulson 1989; Linklater

2000), but the body size and weight of horses is greater by an order of magnitude (Dawson

1995; Fletcher 2006; Csurhes et al. 2009). Smaller species rarely dominate larger species

(Morse 1974). In the North American rangelands, feral horses are subordinate only to bison

(Bison bison) and dominant over numerous herbivores including cattle (Bos taurus) and

desert bighorn sheep (Berger 1986; Coates and Schemnitz 1994; Mosley 1999). Feral horses

have been observed to directly interfere with subordinate Great Basin Desert ungulates

(Berger 1985) and cattle with red kangaroos and eastern grey kangaroos (Kaufmann 1975;

Croft 1980; Payne and Jarman 1999). Aggressive acts are uncommon, as once the dominance

hierarchy is established, interspecific social competition largely becomes a passive process

(Mosley 1999). When resources are adequate across the landscape, but not to the extent

that animals can ignore each other’s presence, the subordinate species usually adjust their

spatial relationships relative to dominant animals to avoid conflict (Mosley 1999). Desert

bighorn sheep, for example, have been observed to never to use a watering point at the

same time as feral horses, nor when feral horses were within sight of the watering point, and

can wait hours for feral burros to leave a water source before approaching for a drink (Dunn

and Douglas 1982; Ostermann-Kelm et al. 2008). A manipulative field experiment involving

tethered domestic horses confirmed indirect interspecific competition as the mechanism

(Ostermann-Kelm et al. 2008). Eastern grey and red kangaroos also dissociate from cattle in

paddocks ranging in size from 0.1–3680 ha in semi-arid and arid environments, and a

behavioural mechanism could not be ruled out (Low and Low 1975; Southwell and Jarman

1987; Payne and Jarman 1999). There is sufficient overlap in the activity cycles of horses and

eastern grey kangaroos for initial behavioural antagonism to have occurred to establish a

precedent. Kangaroos are primarily nocturnal grazers, but eastern grey kangaroos are one of

the most diurnally active species of macropod along with the red-necked wallaby (Macropus

rufogriseus) (Kaufmann 1974, 1975; Clarke et al. 1995). Feral horses are diurnal and

crepuscular and can spend up to 70% of a 24-hour period grazing (Duncan 1985); both

species rest in the middle of the day in similar habitat types (Caughley 1964; Taylor 1980;

McCort 1984).

This is the first study to provide empirical evidence of macropods altering their

spatial distribution and potentially their foraging behaviour in relation to manipulated

numbers of feral horses. On the basis of this study and the literature, exploitative

competition and indirect interference competition were both plausible causal mechanisms.

Chapter 3. Indirect Effects on Macropods 84

A well-designed manipulative experiment would be required to understand the mechanism

underlying the dissociation between horses and macropods on Paddys Plateau and in the

gorge catchments.