Aust. Wildl. Res., 1986, 13, 1-6

The Habitat, Distribution and Conservation Status of the Tasmanian Bettong, Bettongia gaimardi (Desmarest)

R. W. Rose Zoology Department, University of Tasmania, Box 252C, G.P.O., Hobart, Tas. 7001.

Abstract

The Tasmanian bettong, Bettongia gaimardi, appears to be the most common member of its genus. Though formerly distributed on the Australian mainland, B. gaimardi is now found only in the open forest habitats of eastern Tasmania, the vast majority of which are susceptible to forestry operations, such as clearfelling, burning and the laying of 1080 poison. Unless carefully managed, all of these practices in the long term are likely to reduce bettong populations. This and the fact that only 5% of bettong habitat lies within National Parks, leads to the conclusion that the conservation status of this species should be regarded as 'vulnerable'.

Introduction

The Tasmanian bettong has the most secure status of any member of the seriously depleted genus Bettongia (Johnson and Rose 1983). However, surprisingly little information has been published on this small rat-kangaroo. Wakefield (1967), on the basis of skull morphology, synonomized the Tasmanian species (then B. cuniculus) with the Australian mainland form, B. gaimardi, but considered the Tasmanian population should be given subspecific status: B. gaimardi cuniculus. The mainland form (B. g. gairnardi) is believed to be extinct (Poole 1979), having suffered a dramatic decline in range and numbers since the advent of European man and his introduced eutherian mammals. Fire and the introduction of the fox and rabbit are thought to have had a major role in the marked contraction in the distribution of the genus (Jones 1924; Christensen 1980; King et al. 198 1).

This paper discusses the distribution of the Tasmanian bettong and describes its habitat and conservation status.

Distribution

B. g. gairnardi was formerly distributed along the coastal areas of eastern Australia, from south-east Queensland to the south-east tip of South Australia (Wakefield 1967). On the basis of the distribution maps in Burbidge (1983) and Christensen (1983), it may have been allopatric with south-eastern populations (now extinct) of Bettongia lesueur and B. penicillata.

Today the Tasmanian bettong is found over most of the eastern half of Tasmania (Fig. 1) and extends to parts of the central highlands at altitudes above 1000 m. Populations occur on Bruny I. and Maria I. but not on the larger Bass Strait islands, King I. and Flinders I., nor is there evidence of them having been there in the recent past (Hope 1973). Le Souef (1929) states that '. . . another species of Rat-Kangaroo, probably Bettongia cuniculus ( = gaimardi) is reported as still being occasionally seen on Flinders and Barren islands.' Aepyprymnus rufescens has been found as a sub-fossil on Flinders I. (Hope 1973) and it is possible that Aepyprymnus was identified as Bettongia. The absence of B. gairnardi from all Bass Strait islands is intriguing in view of

03 10-78331861010001$02.00

R. W. Rose

its distribution on both sides of the strait. One explanation may be that these islands were covered with thick shrubland until cleared within the last 180 years (Guiler 1967), so that bettong habitats were not available (Hope 1973).

There has been no systematic survey of the present distribution of the bettong in Tasmania, and as there is little historical data in the literature and museum records, it is not known if its range has contracted. However, there can be no doubt that its distribution is far more patchy at present than in the past. Certainly, the following quotation from Gould (1863) is no longer correct: '. . . Few of the indigenous quadrupeds of Van Diemen's Land are better known than the present, which may be said to be universally dispersed over that island, wherever localities occur favourable to its habits and mode of life . . .'.

Fig. 1. The distribution of the Tasmanian bettong (e) plotted on a 10-km grid; some points represent more than one record. Based on published records (see References), personal communications, the Tasmanian National Parks and Wildlife Service files (1967-84) and the author's own records (1976-84). Stippled areas, open forest (from Jackson 1965).

Habitat

The distribution of the Tasmanian bettong coincides with that of open forest [as defined by Specht et a/. (1974) and mapped by Jackson (1965)l. In Fig. 1, many of the points that appear outside the region of open forest are in smaller pockets of this forest (Kirkpatrick and Dickinson 1984; Jackson, personal communication) that are not included in Jackson's (1965) vegetation map.

Details of the habitat are available for some of the trapping sites where bettongs were caught. The understorey (Fig. 2) is usually low (0-1 m) and comprises a number of grass species, e.g. tussock grass Poa rodwayi, wallaby grass Danthonia sp., and browntop Agrostis sp. The most

Status of Tasmanian Bettong

common understorey species is common sag Lomandra longifolia. In recently burnt areas bracken Pteridium sp. may be common. Other ground species include everlasting daisy Helichrysum sp., Hibbertia spp., and guitar plant Lomatia tinctoria, and in wetter areas cutting grass Gahnia sp., cord rush Restio sp., and sedge Empodisma minor. Heath species, such as Epacris sp. and beard-heath Leucopogon collinus, are present in sandy areas. Medium-sized shrubs (0-3 m) consist mainly of Leptospermum sp. and Melaleuca sp., and in sandy areas Banksia marginata.

Eucalyptus obliqua, E. viminalis or E. amygdalina, and to a lesser extent Acacia dealbata, Casuarina stricta and native cherry Exocarpos cupressiformis are the dominant tree species. In the more elevated regions of the Central Highlands, E. coccifera and E. pauciflora may predominate, as may E. rodwayi in wetter sites.

Fig. 2. Typical habitat of the Tasmanian bettong in south-eastern Tasmania: Eucalyptus viminalis with Lomandra longifolia.

Most bettong habitat in open forest areas is situated on infertile dolerite soils, although occasionally on granite or sandstone. With the exception of the Central Highlands, much of which can be covered with snow for extended periods, the bettong is found only in the warmer parts of Tasmania with relatively low rainfall (50-75 mm per annum). Gould was correct when he informed Waterhouse (1846) that in Tasmania the bettong '. . . prefers the open sandy or stony forest land rather than the thick and humid brushes . . .'.

Nests

Bettongs build densely woven nests of dry grass and bark, which they conceal with considerable skill under fallen limbs, among clumps of short bushes or at the base of tussocks. They have a prehensile tail with which they transfer nest material, as do other bettongs (Gould 1863; Johnson and Rose 1983). One bettong was obtained from the wild (north-eastern Tasmania) with a tail still grasping vegetation, presumably for nest construction. This comprised a pteridophyte (Selaginella), grass (hairy rice grass Tetrarrhena sp.), and rushes (cord rush, Restio sp.); the weight of the package was approximately 100 g. One nest (at Kempton) contained three species of grass (Danthonia sp., Poa rodwayi and Agrostis sp.) and was wrapped in a basket of leaves and bark of Eucalyptus obliqua. The nest also contained seeds from a number of commercial crops including

R. W. Rose

millet, sorghum, oats, maize, wheat and sunflower. Further details on nest composition and sites may be found in Kershaw (1952, 1971) and Johnson (1979).

Conservation Status

Only in Tasmania are bettongs relatively common. It is tempting to attribute the principal cause of the mainland decline to the fox, which has not been established in Tasmania. However, rabbits never reached the abundance in Tasmania that they did on the mainland, and consequently may not have been so destructive of the habitat favoured by the bettong; this in turn may have allowed the bettong to maintain levels of population in Tasmania not found on the Australian mainland (Johnson and Rose 1983). Perhaps it is prudent to withhold judgment on this question, because several other species of marsupial are more abundant in Tasmania than on the Australian mainland, e.g. Thylogale billardierii, Potorous tridactylus, Perameles gunnii and Dasyurus viverrinus.

At present, 5070 of Tasmanian habitat suitable for the bettong is in areas under private ownership and susceptible to forestry and agricultural development; 45% is in areas controlled by the Crown (though also susceptible to forestry and other development); and only 5% lies within lands designated National Parks (Rose 1985). The bettong is found naturally in four Tasmanian National Parks (Freycinet, Asbestos Range, Mt Field and Mt William) and has been introduced into a fifth (Maria I.; D. Rounsevell, personal communication). It is totally protected throughout its range; none the less, its status must be regarded as vulnerable. It is not known whether the bettong is prey to feral cats, but the further introduction of other eutherian predators (such as the Cox) could endanger it. Both of these predators have been implicated in the decline of Bettongia on the Australian mainland (Jones 1924: King et al. 198 1). The western quoll, Dasyurus geoffroii, is a major predator of Bettongia lesueur (Christensen 1980), but although the eastern quoll D. viverrinus feeds occasionally upon small mammals (Green 1967), it is unlikely to prey upon the Tasmanian bettong, because they have been kept together in captivity for lengthy periods (Rose, unpublished data). It is possible that the larger tiger quoll, D. maculatus, preys upon the bettong.

Forestry practices are likely to have an impact on the distribution of the bettong. Clearfelling for the purpose of woodchipping did not have an immediate impact on bettong numbers in two areas at Buckland (Gowland 1977). In the short term, populations tended to increase immediately after copses were burnt (Kershaw 1971; Gowland 1977). However, Johnson (1978) speculates that burning undoubtably reduces the availability of suitable nest sites and nest material for bettongs; the transient return of animals to these areas may be because they are able to carry their own nesting material in their prehensile tails. Also, the hypogean fungi on which they are dependent (Rose 1982, l985), may not be affected immediately by above-ground forestry practices, as suggested by Christensen (1980). However, as forest regeneration proceeds, bettong populations dwindle and no individuals were recorded by Gowland (1977) 2 years after burning. Johnson (1978) suggests that management of bettong habitat would require the exclusion of fire until it became necessary to reduce the shrub layer. He suggests that fire could be then used in patches, but not as a blanket treatment.

The susceptibility of the Tasmanian bettong to poisoning by 1080 is comparable to that of most species of herbivorous animals (King et al. 198 1; McIlroy 1982). Statham (1983) found that the laying of 1080 poison resulted in a 50% decline in two populations of the bettong in Tasmania. Although she concluded that some bettong populations would probably recover after once-off poisonings, it seems likely that the laying of poisoned bait, if continued, will inevitably result in a decline in bettong density. Small isolated populations would suffer most, because there is little likelihood of recolonization after disturbance (Statham 1984).

The Tasmanian bettong is relatively abundant and widespread compared with other species of Bettongia. However, it remains vulnerable because of susceptibility to the introduction of eutherian predators, and changes in land use, e.g. escalation of forestry practices. As only a small percentage of its preferred habitat is protected in National Parks; and in order to ensure that

Status of Tasmanian Bettong

it does not suffer the same fate as its mainland congeners, detailed ecological studies are required. Work has started on this project in 1985 (R. Taylor, personal communication).

Acknowledgments

I thank all those members of the Zoology Department, University of Tasmania, who assisted in this project; in particular Dr R. Swain, Dr R. Taylor, R. Mawbey and R. Holrnes. The following provided unpublished records for Fig. 1: H. Statham, Forestry Commission; R. H. Green, Queen Victoria Museum, Launceston; P. Andrews, Tasmanian Museum and Art Gallery, Hobart. J. Bayly-Stark, G. Hocking and D. Rounsevell, from the Tasmanian National Parks and Wildlife Service, were most helpful in criticizing this manuscript and providing many records for the distribution map.

References

Burbidge, A. A. (1983). Burrowing bettong, Bettongia lesueur. In 'The Complete Book of Australian Mammals'. (Ed. R. Strahan.) pp. 187-9. (Angus and Robertson: Sydney.)

Christensen, P. (1 980). The biology of Bettongia penicillata Gray, 1837 and Macropus eugenii Desmarest, 1834 in relation to fire. West. Aust. Dep. For. Bull. No. 91.

Christensen, P. (1983). Brush-tailed bettong, Bettongia penicillata. In 'The Complete Book of Australian Mammals'. (Ed. R. Strahan.) pp. 184-5. (Angus and Robertson: Sydney.)

Flynn, T. T. (1930). The uterine cycle of pregnancy and pseudo-pregnancy as it is in the diprotodont marsupial Bettongia cuniculus. Proc. Linn. Soc. N.S. W. 55, 506-31.

Green, R. H. (1967). Notes on the Devil (Sarcophilus harrisii) and the Quo11 (Dasyurus viverrinus) in northeastern Tasmania. Rec. Queen Victoria Mus. 27, 1 - 1 3.

Gould, J. (1863). 'The Mammals of Australia.' Vol. 2. (The Author: London.) Gowland, P. N. (1977). Vertebrate fauna of the Buckland training area, Tasmania. CSIRO Div. Land Res.

Tech. Mem. No. 77112. Guiler, E. R. (1960). 'Marsupials of Tasmania.' (Tasmanian Museum and Art Gallery: Hobart.) Guiler, E. R. (1967). The Cape Barren Goose, its environment, numbers and breeding. Emu 66, 21 1-35. Hope, J. H. (1973). Mammals of the Bass Strait Islands. Proc. R. Soc. Victoria 85, 163-96. Jackson, W. (1965). Vegetation. In 'Atlas of Tasmania'. (Mercury Walsh: Hobart.) Johnson, K. A. (1978). Methods for the census of wallaby and possum in Tasmania. Tasmanian Natl Parks

Wildl. Serv. Tech. Rep. Johnson, K. A. (1979). Construction and site selection of nests by Gaimard's rat kangaroo, Bettongia gaimardi,

in Tasmania. Bull. Aust. Mamm. Soc. 6, 29. Johnson, K. A., and R. Rose. (1983). Tasmanian bettong, Bettongia gaimardi. In 'The Complete Book

of Australian Mammals'. (Ed. R. Strahan.) p. 186. (Angus and Robertson: Sydney.) Jones, F. Wood (1924). 'The Mammals of South Australia.' Part 11. (Government Printer: Adelaide.) Kershaw, R. (1952). Notes on marsupials at the Tamar River, Tasmania. Victorian Nat. 69, 102-5. Kershaw, R. (1971). Notes on Tasmanian rat kangaroos. Victorian Nat. 88, 4-10. King, D. R., Oliver, A. J., and Mead, R. J. (1981). Bettongia and fluoroacetate: a role for 1080 in fauna

management. Aust. Wildl. Res. 8, 529-36. Kirkpatrick, J. B., and Dickiison, K. J. M. (1984). 'Vegetation of Tasmania.' (Forestry Commission, Tasmania:

Hobart.) Le Souef, A. S. (1929). Notes on some mammals from Bass Strait islands, including a new subspecies of

Pseudocheirus. Aust. Zool. 5, 329-32. McIlroy, J. C. (1982). The sensitivity of Australian animals to 1080 poison. 111. Marsupial and eutherian

herbivores. Aust. Wildl. Res. 9, 487-504. Poole, W. E. (1979). The status of the Australian Macropodidae. In 'The Status of Endangered Australasian

Wildlife'. (Ed. M. J. Tyler.) pp. 13-27. (Royal Zoological Society of South Australia: Adelaide.) Rose, R. W. (1 982). Tasmanian bettong Bettongia gaimardi: maintenance and breeding in captivity. In 'The

Management of Australian Mammals in Captivity'. (Ed. D. D. Evans.) pp. 108-10. (Royal Zoological Society of Victoria: Melbourne.)

Rose, R. W. (1985). The reproductive biology of the Tasmanian bettong, Bettongia gaimardi. Ph.D. Thesis, University of Tasmania.

Specht, R. L., Roe, E. M., and Broughton, V. H. (1974). Conservation of major plant communities in Australia and Papua New Guinea. Aust. J. Bot. Suppl. Ser. No. 7.

R. W. Rose

Statham, H. L. (1983). Browsing damage in Tasmanian forest areas and effects of 1080 poisoning. Tasmania For. Comm. Bull. No. 7.

Statham, H. L. (1984). The effects of forest operation on wildlife in Tasmania. (Literature review submitted to the Forest Ecology Research Fund, Tasmania.)

Wakefield, N. A. (1967). Some taxonomic revision in the Australian marsupial genus Bettongia (Macropodidae) with descriptions of a new species. Victorian Nat. 88, 8-22.

Waterhouse, G. (1 846). 'Natural History of the Marnmalia. Vol. 1. Marsupialia, or Pouched Animals.' (London.)

Manuscript received 1 February 1985; accepted 1 3 May 1985