Carbon Isotopic Assessment OF THE Diets OF Elephants IN Kruger National Park–Seasonal AND Spatial Variability

ECOSYSTEM RESOURCES INFLUENCING ELEPHANT POPULATIONS..................................... 44

HISTORY OF THE KNP ELEPHANT POPULATION........................................................................................... 44Ian Whyte ................................................................................................................................................. 44

Rate of recolonisation of Kruger National Park by elephants.............................................................. 46BACKGROUND TO ELEPHANT POPULATION GROWTH................................................................................... 49

Ian Whyte ................................................................................................................................................. 49Birth rate .............................................................................................................................................. 49Death Rate............................................................................................................................................ 50

THE EFFECTS OF LONG-TERM ARIDITY AND DROUGHT EFFECTS ON ELEPHANT POPULATIONS .................. 55Keith Leggett............................................................................................................................................ 55

Implications for management/decision-making................................................................................... 56Reliability of hypothesis ...................................................................................................................... 56Biodiversity Consequences.................................................................................................................. 56Future Research ................................................................................................................................... 57

RAINFALL DRIVERS OF DRY SEASON SAVANNA PRODUCTIVITY .................................................................. 58Simon Chamaillé & Hervé Fritz .............................................................................................................. 58

CONTRIBUTION FROM THE HERD PROJECT, HWANGE ZIMBABWE, TO THE SANPARKS WORSHOP ON ELEPHANT AND BIODIVERSITY .................................................................................................................... 59

Hervé Fritz............................................................................................................................................... 59NUTRITIONAL REQUIREMENTS OF ELEPHANT OF PROTEIN AND ENERGY..................................................... 61

H.H. Meissner .......................................................................................................................................... 61Food selection ...................................................................................................................................... 61Management implications.................................................................................................................... 62

CARBON ISOTOPIC ASSESSMENT OF THE DIETS OF ELEPHANTS IN KRUGER NATIONAL PARK – SEASONAL AND SPATIAL VARIABILITY ......................................................................................................................... 63

J. Codron, Julia A. Lee-Thorp, M. Sponheimer, C.C. Grant, D. Codron................................................. 63Geographical and seasonal variation in elephant diet composition using faecal samples ................... 64Variation in elephant diet composition over time using ivory samples ............................................... 65Management implications.................................................................................................................... 66Biodiversity consequences................................................................................................................... 66Research requirements ......................................................................................................................... 67

CANAFRICAN ELEPHANTS (LOXODONTA AFRICANA) SURVIVE AND THRIVE INMONOSTANDSOF COLOPHOSPERMUM MOPANEWOODLANDS?..................................................................................... 68

D.D.G. Lagendijk, W.F. de Boer and S.E. van Wieren............................................................................ 68Management implications.................................................................................................................... 69Biodiversity consequences................................................................................................................... 69Research requirements ......................................................................................................................... 69Key publications .................................................................................................................................. 70

HISTORICAL HUMAN – ELEPHANT INTERACTIONS RELATING TO ELEPHANT POPULATIONS ........................ 74Charles E. Kay......................................................................................................................................... 74

Research requirements ......................................................................................................................... 75Management implications.................................................................................................................... 76

ECOSYSTEM RESOURCES INFLUENCING ELEPHANT POPULATIONS .............................................................. 77Norman Owen-Smith................................................................................................................................ 77

Management implications.................................................................................................................... 77SUMMARY AND CONCLUSIONS..................................................................................................................... 79

Norman Owen-Smith................................................................................................................................ 79The knowledge base............................................................................................................................. 79Implications for further research and management.............................................................................. 83

44

ECOSYSTEM RESOURCES INFLUENCING ELEPHANT POPULATIONS

HISTORY OF THE KNP ELEPHANT POPULATION

IAN WHYTE

The increase in the population up to 1967 are summarised in Table 1 along with the nature of the estimate and the source reference.

It is clear from this that the increase between the years 1960 and 1967 could not have been due to biological increase alone. It is likely that the estimated totals prior to 1967 were under-estimates and that the first aerial census yielded a result much closer to the actual figure, suggesting the apparent massive increase over this period. It is unlikely that any of the estimates prior to 1967 have any real value compared with the latter ones using aerial census techniques. A second curve has been fitted to the graph by eye which is likely to resemble the actual population increase more closely. This would reflect biological increase and immigration from the neighbouring territories (Zimbabwe (Rhodesia) and Mozambique) as well.

Table 1: Estimates of numbers of elephants in the Kruger National Park from 1903-1967.

Year Number Nature of estimate Source

1903 0 Estimate Stevenson-Hamilton (1903a, 1903b)1905 10 Estimate Stevenson-Hamilton (1905)1908 25 Estimate Stevenson-Hamilton (1909)1925 100 Estimate Stevenson-Hamilton (1925)1931 135 Estimate c.f. Pienaar, van Wyk & Fairall (1966)1932 170 Estimate Stevenson-Hamilton (1932)1933 200 Estimate Stevenson-Hamilton (1933)1936 250 Estimate Stevenson-Hamilton (1936)1937 400 Estimate Stevenson-Hamilton (1937)1946 450 Estimate Sandenberg (1946)1947 560 Estimate c.f. Pienaar, van Wyk & Fairall (1966)1954 740 Estimate Steyn (1958)1957 1 000 Estimate Steyn (1958)1960 1 186 Aerial survey c.f. Pienaar, van Wyk & Fairall (1966)1962 1 750 Fixed-wing survey Pienaar (1963)1964 2 374 Helicopter count * Pienaar, van Wyk & Fairall (1966)1967 6 586 Helicopter count * Pienaar (1967)

45

Limpopo R.

Luvuvhu R.

Mutale R.PAFURI

PUNDA MARIA

Nwam

biya

MALELANE

CROCODILEBRIDGE

Crocodile R.

Sabie R.

Sand R.

PRETORIUSKOP

SKUKUZA

LOWERSABIE

TSHOKWANE

ORPEN

NWANETSINwaswitsonso

TimbavatiSweni

SATARA

Mbyamiti

OLIFANTS

LETABA

PHALABORWA

Olifants R.

MAHLANGENI

MOOIPLAAS

KleinLetaba

SHANGONI SHINGWEDZIShingwedzi

Bububu

Phugwane

Mphongolo

Tsende

19091925

1931

1933

First recorded1913

1931

1938

1939

1934 1909

1937

1940

1941

1941

1941

1942

1952

1945

1943

19461958

1934

1938

1945

C:\THESISFL\ELERECOL.DRW

in 1905

MOZAM

BIQUE

1958

10 20 30 40 50 km0

S

N

W E

Figure 1: Elephant recolonisation of the Kruger National Park between 1903 and 1958

46

In 1967, annual aerial censusing of the population as well as population control (culling) were initiated. This signalled the start of the “Management era” during which the policy was to hold the population at a level of around 7 000.

Rate of recolonisation of Kruger National Park by elephants

The pattern of recolonisation of the KNP by elephants subsequent to 1903 (when there were no elephants) and up to 1958 (when they had finally been recorded throughout the area) is shown in Figure 1. These data and localities were derived from the reports of the earlier rangers and wardens given above.

The change in elephant population is illustrated in Fig.1.

ANNUAL CENSUSES ANDCULLING INITIATED 1967

POPULATION GROWTHACCORDING TO ESTIMATES

MORE LIKELY POPULATION GROWTH(NATURAL INCREASES AND IMMIGRATION)

POPULATION CEILING: 7 000

KNP ELEPHANT POPULATION TRENDS: 1903 KNP ELEPHANT POPULATION TRENDS: 1903 KNP ELEPHANT POPULATION TRENDS: 1903 KNP ELEPHANT POPULATION TRENDS: 1903 ---- 2004200420042004

1900190019001900 1910191019101910 1920192019201920 1930193019301930 1940194019401940 1950195019501950 1960196019601960 1970197019701970 1980198019801980 1990199019901990

10101010

9999

8888

7777

6666

5555

4444

3333

2222

1111

0000

POPULATION ESTIMATE (X 1000)

YEAR OF POPULATION ESTIMATE2000200020002000

UPPER "ACCEPTABLE" LIMIT: 8 500

LOWER "ACCEPTABLE" LIMIT: 6 000

2004 CENSUS TOTAL: 11 45411111111

MORATORIUM ON CULLING IN 1994

12121212

Period of elephant culling(1967 - 1994)

PREVAILING POLICY BETWEEN 1967 & 1994

Figure 2: Estimates of the Kruger National Park elephant population between 1903 and 2003.

47

BUECHNER, H. K., BUSS, I. O., LONGHURST, W. M. 1963. Numbers and migration of elephants in Murchison Falls National Park, Uganda. Journal of Wildlife Management. 27(1): 36-53.

FAIRALL, N. 1965. Die Invloed van Vrugbaarheid en Natuurlike beheermeganismes in Bevolkingsgroei. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

GLOVER, J. 1963. The elephant problem at Tsavo. East African Wildlife Journal 1: 30-39.KNOBEL, R. 1965. Algemene Beginsels van Natuurbewaring. Proceedings of Symposium on Problems of

Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

LABUSCHAGNE, R.J. 1965. Newe Produkte: Behandeling en Afset. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

NATIONAL PARKS BOARD OF CURATORS. 1966. Minutes of the meeting of 22 March 1966. Typescript. Skukuza, National Parks Board.

PIENAAR, U. de V. 1960. Die status van olifante in die Suidelike Distrik van die Nasionale Krugerwildtuin. Unpublished internal memorandum. Skukuza, South African National Parks.

PIENAAR, U. de V. 1963. Large mammals of the Kruger National Park - their distribution and present-day status. Koedoe 6: 1-137.

PIENAAR, U. de V. 1965. Diere: Gebiede en Populasies: Wenslikheid van Beheer en Beheermetodes. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

PIENAAR, U. de V. 1996. Kommentaar op die besprekings dokument vir die fasilitering van deelname aan die hersienings proses - "Review of the Management Policy of the Kruger National Park" deur A. Hall-Martin & P. Novellie. Unpublished manuscript. Skukuza, South African National Parks.

PIENAAR, U. de V. 1967. 'n Lugsensus van olifante en ander grootwild in die hele Krugerwildtuin gedurende September 1967. Unpublished internal memorandum. Skukuza, South African National Parks.

PIENAAR, U. de V., VAN WYK, P. & FAIRALL, N. 1966. An aerial census of elephant and buffalo in the Kruger National Park and the implications thereof on intended management schemes. Koedoe 9: 40-107.

RAAD VAN KURATORE VIR NASIONALE PARKE. 1967. Een-en-veertigste Jaar-verslag. Pretoria: South African National Parks.

SANDENBERGH, J.A.B. 1946. Kruger National Park, Warden's Annual Report 1946. Unpublished internal memorandum. Skukuza, South African National Parks.

STEVENSON-HAMILTON, J. 1903a. Report on Singwitsi Game Reserve. Transvaal Administration Reports for 1903. Unpublished internal memorandum. Sabie Bridge.

STEVENSON-HAMILTON, J. 1903b. Game Preservation. Transvaal Administration Reports for 1903. Unpublished internal memorandum.

STEVENSON-HAMILTON, J. 1905. Report on the Government Game Reserves for the year ended 30th June 1905. Unpublished internal memorandum.

STEVENSON-HAMILTON, J. 1909. Report on Government Game Reserves. Annual Report 1908-9. Unpublished internal memorandum. Skukuza, South African National Parks.

STEVENSON-HAMILTON, J. 1925. Extracts from the annual report of the Transvaal Game Reserves. 1925. Unpublished internal memorandum. Skukuza, South African National Parks.

STEVENSON-HAMILTON, J. 1932. Kruger National Park, Warden's Annual Report 1932. Unpublished internal memorandum. Skukuza, South African National Parks.




48

STEYN, L.B. 1942. Extract from diary, 21 May, 1942. South African National Parks Archives. Skukuza, South African National Parks.

STEYN, L.B. 1958. Jaarverslag van die Opsiener: Nasionale Krugerwildtuin vir die tydperk 1 April 1957 tot 31 Maart 1958. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN DER MERWE, N. 1965. Publisiteit. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN NIEKERK, J. 1965. Kontrole deur Middel van Siektes en Parasiete. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN WYK, P. & FAIRALL, N. 1969. The influence of the African elephant on the vegetation of the Kruger National Park. Koedoe 12: 66-75.

-HAMILTON, J. 1932. Kruger National Park, Warden's Annual Report 1932. Unpublished internal memorandum. Skukuza, South African National Parks.




STEYN, L.B. 1942. Extract from diary, 21 May, 1942. South African National Parks Archives. Skukuza, South African National Parks.

STEYN, L.B. 1958. Jaarverslag van die Opsiener: Nasionale Krugerwildtuin vir die tydperk 1 April 1957 tot 31 Maart 1958. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN DER MERWE, N. 1965. Publisiteit. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN NIEKERK, J. 1965. Kontrole deur Middel van Siektes en Parasiete. Proceedings of Symposium on Problems of Over-protection of Wildlife. Unpublished internal memorandum. Skukuza, South African National Parks.

VAN WYK, P. & FAIRALL, N. 1969. The influence of the African elephant on the vegetation of the Kruger National Park. Koedoe 12: 66-75.

49

BACKGROUND TO ELEPHANT POPULATION GROWTH

IAN WHYTE

Birth rate

Normal expected population growth

• Maximum rate of increase for an elephant population was estimated by Calef (1988) to be 7% per annum.

Established populations

• The mean population growth rate in KNP has been estimated at 6.6% (Whyte 2001), which has been confirmed by van Aarde (pers comm. 2004) through an independent estimate. Estimates from other populations range from 3.75% in Amboseli (Moss 2001) and 5.2% in Addo (Woodd 1999). KNP’s population growth is thus very close to biological potential.

• One of the main determinants of population growth rate is the Mean Calving Interval (MCI). Many differing MCIs have been reported for elephant in the literature but Moss (2001) has pointed out that as gestation time is close to two years, and MCI would normally be in excess of three years, the calculation of MCI on a single year’s sample is likely to be erroneous. Many cows may conceive in response to a good rainfall period, resulting in an increased calf % two years later, but in the subsequent 2-4 year period, this will be reduced. In KNP Whyte (2001) recorded annual MCIs ranging from 2.8 to 5.1 between 1976 and 1995 with a mean of 3.7 years. Laws et al. (1975) have shown that east African populations have variable birth rates. Comparing MCIs which were derived from short-term sampling is therefore invalid. Lindeque (1988) summarised the known MCIs from various studies (Table 1).

Table 1 Respective mean calving intervals (MCI) reported for various elephant populations in Africa.

LOCALITY MCI REFERENCE

Kabalega Falls NP (North)

Kabalega Falls NP (South)

Tsavo National Park

Kruger NP

Kruger NP

Luangwa Valley NP

Gonarezhou NP

Hwange NP

Etosha NP (1983 & 1985)

4.5

4.6

6.8

4.5

3.7

3.5

3.7

4.0

3.8

Laws (1969)

Laws (1969)

Laws (1969); Laws & Parker (1968)

Smuts (1975)

Whyte (2001)

Hanks (1972); Malpas (1978)

Sherry (1975)

Williamson (1976)

Lindeque (1988)

50

A skewed foetal sex ratio favouring females would also influence population growth, but no study has reported a foetal sex ratio that deviates from 1:1. In KNP, a foetal sex ratio calculated from a sample of 624 foetuses collected at culls was 311 : 313 (Whyte 2001).

1.1 Growing populations

Some populations established from translocated animals have reported growth rates of over 10% per annum (Garai et al. 2004). These are almost certainly the result of imbalances in the sex ratios of introduced populations, and perhaps also with an initial high proportion of pubertal females. With time as a normal population structure establishes itself, these high rates of population growth would not be sustained.

Death Rate

Causes of juvenile mortality

Very few cases of juvenile deaths have been recorded in KNP as small carcasses would be quickly consumed by predators and scavengers. Such mortalities would have usually been due to abandonment by, or separation from their mothers or predation resulting from this. Moss attributed 61% (n=131) of juvenile mortality to “natural causes” in Amboseli, but did not list these.

Causes of adult mortality

In KNP the mean annual mortality rate was estimated at 3.2% (Whyte 2001). Mortality in adult elephants can be attributed to natural causes, poaching and disease. Since 1980, only 321 elephants have been poached in KNP, of which 200 (62%) occurred in the period 1980 to 1985. Little information is available on the causes of “natural mortality” but most are probably related to the effects of ageing, fire and fighting among males. In KNP an outbreak of Encephalomyocarditis (EMC) caused a cluster of elephant deaths in December 1993 (Grobler et al. 1995). To date 72 animals are known to have died of EMC of which 68 (94%) were adult bulls (Bengis Pers. comm.). Archival records revealed that prior to the outbreak, sporadic unexplained deaths of a further 48 animals had occurred (of which 33 were mature bulls) in widely scattered areas since 1987 (Grobler et al. 1995). Anthrax is a known killer of elephants but since 1990 only 8 have been recorded in KNP (Bengis Pers. comm.). In Etosha, Namibia however the incidence of anthrax is much higher in elephants, where 474 were recorded over the 28 years preceding 1992 (Lindeque & Turnbull 1994). Fire has caused approximately 60 mortalities in elephants in KNP over the past 15 years (data not immediately available).

3. Factors leading to immigration.

Increasing human densities are known to displace elephants. Hoare & du Toit showed that in north-eastern Zimbabwe, elephant and humans could not co-exist where human densities exceed 15/km2. In many places in Africa this has led to elephants moving into conservation areas (e.g. Tsavo), and may also have occurred in KNP between 1964 and 1967 (Whyte 2001).

4. Factors leading to emigration

While elephants in KNP usually have established home ranges (Whyte 1993; 2001), they may change in response to expansion of available habitats. Until the removal of the KNP’s western boundary fence in 1993, there were only very few elephants present in the Sabie-Sand Wildtuin (SSGR) (Table 2), some of which were there as a result of an earlier translocation of juvenile elephants from KNP. Since the removal of the fence, it is clear that there has been significant emigration from KNP which has raised the population growth rate in SSGR way above that which is possible from reproduction alone (Whyte 2004a; 2004b).

51

Table 2 Comparative elephant population trends and densities (elephants per km2) in the Kruger National Park, Associated Private Nature Reserves (APNRs) and Sabie-Sand Private Game Reserve.

KNP (18 985km2) Sabie-Sand (572 km2) APNRs (1 266km2)Year

Count Density Count Density Count Density

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

7834

7806

8064

8320

8371

8869

9152

8356

9276

10459

11672

11454

0.41

0.41

0.42

0.44

0.44

0.47

0.48

0.44

0.49

0.55

0.61

0.60

60

116

202

202

311

429

497

531

601

757

689

757

0.10

0.20

0.35

0.35

0.54

0.75

0.87

0.93

1.05

1.32

1.20

1.32

424

511

526

355

759

617

636

726

824

927

1092

725

0.33

0.40

0.42

0.28

0.60

0.49

0.50

0.57

0.65

0.73

0.86

0.57

On the other hand, the Klaserie/Timbavati complex of reserves, known as the Associated Private Nature Reserves (APNRs), had elephant densities very similar to those in KNP, (see Table 1). Since the removal of the fence between these reserves and KNP, the subsequent growth rates in the respective populations differed markedly. The intrinsic growth rates ( r̄) between 1993 and 2003 were 0.034 for KNP, 0.088 for the APNRs and 0.231 for SSGR. SSGR has experienced a massive population growth, which can only be as a result of an influx from KNP, while that of the APNRs was not far from the 0.66% recorded for KNP during the years that it was fenced entirely (Whyte 2001). On the other hand, KNP’s rather reduced rate over the period would have been the result of the negative influences of culls (n = 552), translocations (n = 657) and emigration into SSGR (Whyte 2004b).

Moss (1988) described that elephant families belonging to a particular home range will defend them from intrusion by other families. The significance of this is that where elephants are already established in home ranges, overlap between neighbours is limited. At the time the fence was removed, the APNRs already had established residents while SSGR did not. Emigration of elephants from KNP into the APNRs did not occur whereas a large influx occurred into SSGR, which had ‘vacant’ home ranges. SSGR now has the highest density of elephants in South Africa. This same trend may be expected for Limpopo National Park when the whole fence is finally removed.

Controllers

5.1 Water requirements

52

• Water requirements for reproduction No information available on this in the wild

• Distances that pregnant elephants can safely move to water

• No information available on this in the wild

• How regularly should elephants drink when pregnant No information available on this in the wild

• Literature on reproduction rates under scenarios of different water availability. No information available on this in the wild

• Water requirements of adults and juveniles (Young??)

• Distances that can be safely traveled between waterpoints. No information available on this in the wild

• Water requirements for lactation. No information available on this in the wild

• How regularly do elephants have to drink water? (Young??) I have no other info in this

• The effect of waterpoint density on elephant populations. Waterpoint density must have a considerable influence on elephant movement. In KNP where waterpoints (including natural waterpoints) are relatively abundant even in the dry season, elephants have relatively small home ranges (Whyte 2001). In the KNP the range of home range sizes was between 86 – 2776 km2 with a mean of 880 km2 (S.D. = 1 154.6), while in the more arid environments of Namibia, they varied between 2136 – 10738km2 with a mean of 5860km2

(Lindeque & Lindeque 1991). In Botswana are also large as a consequence of the arid nature of their environments (I can find no data on this). In the rainy season, elephants move away from the river as drinking water becomes available in temporary pans, but as the dry season progresses, they are forced to return to the permanent water of the Linyanti and Chobe Rivers. Owing to the huge population, food resources quickly become depleted, and elephants are forced to move longer and longer distances between food and water resources. The energy costs of having to do this can be severe in droughts, and lead to increasing calf and juvenile mortalities. While many people have claimed that it has been the artificial water provision program that has stimulated the growth of the KNP population, there is in fact a considerable number of permanent natural waterpoints distributed throughout KNP in the river systems. It is therefore highly unlikely that elephants will ever be faced with the “Botswana scenario” here in KNP. Natural water distribution is such that even if all artificial waterpoints were closed, the long treks between water and food resources will not be necessary. Food resources are also such that these are unlikely to be limiting before the population has achieved much higher levels, by which time, sever elephant impacts are likely to have been experienced on a park-wide scale.

• Do elephant numbers increase with an increase in waterpoints? The best example of the effect of waterpoint density on elephant numbers probably comes from Hwange National Park (HNP), Zimbabwe. The expansion of the elephant population in HNP was clearly linked to the provision of artificial water supplies. (Conybeare 1991, Cumming 1981). At proclamation in 1928 it was estimated that there were no more than 2000 elephants and 15 perennial water points (Cumming 1981). In the dry season, elephants had to move outside HNP to find water, where they were unprotected from hunting. It was then decided to develop water points by providing boreholes and dams (Davison 1967). By 1960 there were 25 boreholes and 11 000 elephants. In spite of some culling, by 1979 there were 16 000 elephants in HNP and by 1981, there were approximately 70 perennial water points

53

and the elephant population estimate was 20 000 (Cumming 1981). The 2002 estimate for Hwange was 44 500 (Blanc et al. 2003).

• Hwange is largely a sandveld system with very few natural perennial water points. Provision of artificial water therefore allowed elephants to permanently colonize the park in large numbers. I contrast to this, KNP has plenty of natural perennial waterholes in its many permanent and semi-permanent watercourses (KNP water point databases), and provision of artificial ones is unlikely to have had a major influence on immigration or permanent settlement of elephants.

REFERENCESBLANC, J., THOULESS, C.R., HART, J.A., DUBLIN, H.T., DOUGLAS-HAMILTON, I., CRAIG, G.C. &

BARNES, R.F.W. 2003. African elephant status report 2002: An update from the African elephant database. Gland: IUCN/SSC/African Elephant Specialist Group.

CALEF, G.W. 1988. Maximum rate of increase in the African elephant. African Journal of Ecology 26: 323-327.

CONYBEARE, A.M.G. 1991. Elephant Occupancy and Vegetation Change in Relation to Artificial Water Points in a Kalahari Sand Area of Hwange National Park. PhD, University of Zimbabwe.

CUMMING, D.H.M. 1981. The management of elephant and other large mammals in Zimbabwe. In: Jewell, P.A., Holt, S. & Hart, D. (eds.). Problems in management of locally abundant wild animals. New York, Academic Press.

DAVISON. E. 1967. Wankie. Cape Town, Books of Africa.Garai, M.E., Slotow, R., Carr, R.D. & Reilly, B. 2004. Elephant reintroductions to small fenced reserves in

South Africa. Pachyderm 37: 28-36.GROBLER, D.G., RAATH, J.P., BRAACK, L.E.O., KEET, D.F., GERDES, G. H., BARNARD, B.J.H.,

KRIEK, N.P.J., JARDINE, J. & SWANEPOEL, R. 1995. An outbreak of encephalomyocarditis-virus infection in free-ranging African elephants in the Kruger National Park. Onderstepoort Journal Veterinary Research. 62(2): 97-108.

HANKS, J. 1972. Reproduction of elephant (Loxodonta africana) in the Luangwa Valley, Zambia. Journal of Reproduction and Fertility 30: 13-26.

HOARE, R.E. & DU TOIT, J.T. 1999. Coexistence between people and elephants in African savannas. Conservation Biology. 13 (3): 633-639.

LAWS, R.M. 1969. Aspects of reproduction in the African elephant, Loxodonta africana. Journal of Reproduction and Fertility Supplement No. 6: 193-217.

LAWS, R.M., PARKER, I.S.C. & JOHNSTONE, R.C.B. 1975. Elephants and their habitats. Oxford, Clarendon press.

LINDEQUE, M. 1988. Population dynamics of elephants in the Etosha National Park. PhD thesis. University of Stellenbosch, Stellenbosch.

LINDEQUE, M. & LINDEQUE, P.M. 1991. Satellite tracking of elephants in northwestern Namibia. African Journal of Ecology 29: 196-206.

LINDEQUE, P.M. & TURNBULL, P.C.B. 1994. Ecology and epidemiology of anthrax in the Etosha National Park, Namibia. Onderstepoort Journal Veterinary Research. 61 (1) 71-83.

MALPAS, R.C. 1978. The ecology of the African elephant in Ruwenzori and Kabalega Falls National Parks. PhD Thesis. University of Cambridge, Cambridge.

MOSS, C.J. 1988. Elephant memories. Thirteen years in the life of an elephant family. Elm Tree Books, London.

MOSS, C.J. 2001. The demography of the African elephant (Loxodonta africana) population in Amboseli, Kenya. The Zoological Society of London 255: 145-156.

SHERRY, B.Y. 1975. Reproduction of elephant in Gonarezhou, south-eastern Rhodesia. Arnoldia. 29: 1-13.SMUTS, G.L. 1975. Reproduction and population characteristics of elephants in the Kruger National Park.

Journal of the Southern African Wildlife Management Association 5(1): 1-10.WHYTE, I.J. 1993. The movement patterns of elephants in the Kruger National Park in response to culling and

environmental stimuli. Pachyderm 16: 72-80.

54

WHYTE, I.J. 2001. Conservation management of the Kruger National Park elephant population. PhD. Thesis. University of Pretoria, Pretoria.

WHYTE, I.J. 2004a. The ecological basis of the Kruger National Park’s new elephant management policy and expected outcomes after implementation. Pachyderm 36: 99-108.

WHYTE, I.J. 2004b. Census results for elephant and buffalo in the Kruger National Park between 1997 and 2003. Scientific Report 03/04. Internal Report. Skukuza, South African National Parks.

WHYTE, I.J. 2004c. The feasibility of current options for the management of wild elephant populations. In: Proceedings of an expert consultation on the Control of Wild Elephant Populations. Pp 14-16. Utrecht University Library, Utrecht, The Netherlands.

WILLIAMSON, B.R. 1976. Reproduction in female African elephant in Wankie National Park, Rhodesia. South African Journal of Wildlife Research 6: 89-93.

WOODD, A.M. 1999. A demographic model to predict future growth of the Addo elephant population. Koedoe42 (1): 97-100.

55

THE EFFECTS OF LONG-TERM ARIDITY AND DROUGHT EFFECTS ON ELEPHANT POPULATIONS

KEITH LEGGETT

Introduction

Long term aridity and periods of drought can have significant effects on the population density, structure and distribution of elephants. This paper looks at the long-term aridity in northwestern Namibia and the drought of 1991-1992 in Gonarezhou National Park in Zimbabwe.

MethodsI have studied the elephants in northwest Namibia for the last seven years, mainly the population west of Etosha National Park, north of the Hoanib River in the <100mm-rainfall zone. In September 2002 and September 2004, eight and 5 elephants respectively were GPS collared in the focus area. The movements obtained from these collars will be discussed in this paper. Observation methods were used to determine herd structure, fecundity rate, inter-calving periods and onset of puberty. This work has been carried out at the extreme of elephant range in an adverse environment and reflects the ability of elephants to survive in a wide variety of environmental conditions.

In 1993, I studied the effects of the 1991-1992 drought on elephants in Gonarezhou National Park in the southeast lowveld of Zimbabwe. The location, sex and age of 546 elephant skeletons were recorded.

ResultsIn the arid northwest of Namibia, there are 54 elephants in 7 family units and 7-9 free ranging adult males. Elephant population reproductive potentials are limited by the seasonal availability of nutritional forage. The populations have a fecundity rate of 1.8%; this with natural migrations out of the area and problem animal shootings the population remains stable. The home ranges of family units and free ranging adult male varies from almost sedentary to some of the largest home ranges recorded (771 – 12800km2), with seasonal movements of between 45 to 625km.The intercalving periods in the western Namibian females is about 5 years, though I have seen 6 year old still suckling on females with no attempt at weaning. There doesn't appear to be a difference in intercalving period in females between the ages of 15-45. Females older than 45 still reproduce but at a slower rate. There appears to be a wide variation in the onset of puberty, one female was 10-11 at the birth of her first calf, while another female was 18-20 at the birth of her first calf.The 1991-3 drought in the lowveld of Zimbabwe affected a third of the population of elephants with approximately 1500 individuals dying. Drought mainly effected the reproduction potential with all calves less than 8 years of age dying, and most foetuses being aborted or dying with the adult females. The majority of elephants died in close proximity to permanent natural or artificial waterpoints.

Discussion

The large home ranges and seasonal movements of elephants in northwest Namibia are related to the lack of vegetation and scarcity of receptive females for “in musth” males. The low fecundity rate and late onset of puberty are probably also related to the environmental conditions. The

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questions in an arid area are whether the calves are conceived and then aborted at an early stage if environmental conditions are not favourable or are the females simply not ovulating in periods of bad environmental cycles (poor nutrition). Similarly, the onset of puberty is more than likely linked to favourable environmental cycles.In a short term drought (as in the 1991-3 Zimbabwe drought) elephants can suffer catastrophic losses in a very short period of time. Drought is a very efficient culling operation, with only the strongest surviving. During this time elephants dominated the water points and drove away any other large mammal that came to drink. They probably significantly contributed to the population decline in the buffalo, antelope species and hippo populations. Elephants have been proven to be highly effective modifiers of the landscape, and during drought periods the can have a significant impact on vegetation. In Gonarezhou, they had a severe impact on the baobab trees and other lowveld vegetation. It took some vegetation up to 10 years to recover, while others like the baobab trees will take a lot longer and may never recover to their former numbers.

Implications for management/decision-making

Drought is a normal situation in Southern Africa and mitigation for it should be part of a decision-makers guide in any restricted range (i.e. fenced) protected area. Drought can cause the death of a significant number of individuals in a short space of time, while long-term aridity affects the ability of animal populations to reproduce, forage and move. During a drought, elephants tend to monopolise water points depriving other animals of water and probably significantly contributing to a higher death rate amongst these populations. Efforts to reduce (either culling or translocation) an elephant population before the onset of a significant drought would lessen the impacts on flora and fauna. Alternatively, elephant populations should be kept at a pre-determined level (either culling or translocation) that would lessen their impact during a drought event.

Reliability of hypothesis

The effect of aridity on movement, family unit structure, fecundity rates, inter-calving periods and onset of puberty are established fact. So to, are the devastating effects of short-term droughts on animal populations. The effect of elephants on other animal populations during drought is a well-supported hypothesis as is the effect on vegetation.

Biodiversity Consequences

Drought has a significant impact on the biodiversity of protected areas, regardless of the how wellmanaged they may be. There will always be significant losses, however, minimising these losses requires active management. In the modern world most protected areas offer wildlife only a restricted range of movement due to fencing that more often than not keeps domestic stock out of parks rather than wildlife in. Fenced protected areas can fare far worse in drought periods than open range systems that allow animals a greater freedom of movement. However, even open range systems like northwest Namibia (approximately 72000km2), where animals have adapted to long periods of aridity, can suffer during drought events. In the 1981-82 drought 90% of the domestic stock, 40-60% of the antelope species, 80-90% of Hartmanns mountain zebra and 20-30% of the elephants died. These losses while significant, were still smaller than those observed in Gonarezhou National Park where 30-35% of the elephant, 60-70% of the antelope species and 80-90% of the hippo and buffalo died in1991-92 drought. There was also a significant impact on vegetation in both fenced protected and open range systems.

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Future Research

Research is continuing on elephant range movement, herd structure, fecundity rate, inter-calving periods and onset of puberty. Research will continue on the effects of drought when and if they occur, however, statistically only occur 4 times a century and researchers should gather as much information as possible during each drought event.

ConclusionFrom the research in both Zimbabwe and Namibia it is suggested that the effects of a drought events or periods of aridity should be incorporated in any framework for protected area management in Southern Africa.

Key PublicationsCORFIELD, T.F. (1973) Elephant mortality in Tsavo National Park, Kenya. East African Wildlife

Journal. 11: 339-368.HILLMAN, J. C. & HILLMAN, A.K.K. (1977) Mortality of wildlife in Nairobi National Pak

during the drought of 1973-1974. East African Wildlife Journal. 15: 1-18.VILJOEN, P.J. (1988) The ecology of the desert-dwelling elephants Loxodonta Africana

(Blumenbach, 1797) of western Damaraland and Koakoland. PhD Thesis, University of Pretoria, Pretoria, Unpublished. 334 pages.

LEGGETT, K.E.A. (1994), "Implications of the drought on elephants in Gonarezhou National Park - a preliminary report", Report to National Parks and Wildlife, Zimbabwe, Unpublished. 35 pages.

DUDLEY, J.P., CRAIG, G.C., GIBSON, D. ST. C., HAYNES, G. & KLIMOWICZ, J. (2001) Drought mortality of bush elephants in Hwange National Park, Zimbabwe. African Journal of Ecology. 39: 187-194.

LEGGETT, K.E.A., J. FENNESSY AND S. SCHNEIDER, (2003), “Seasonal distributions and social dynamics of elephants in the Hoanib River catchment, northwestern Namibia”, Journal of African Zoology, 38 (2): 305-316.

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RAINFALL DRIVERS OF DRY SEASON SAVANNA PRODUCTIVITY

SIMON CHAMAILLE & HERVE FRITZ

Climate change is affecting the way ecosystems function worldwide. Savanna productivity is strongly linked to seasonal rainfall amount and is therefore threaten by the changes in precipitation patterns predicted to occur in the course of the 21st century. Being one of the largest biome on Earth, savannas are central in rural human lifestyle sustainability and biodiversity conservation issues. Using remote sensing information on precipitation and vegetation productivity in multiple protected areas in Eastern and Southern Africa, we show that monthly rainfall have different effects on vegetation productivity along the seasonal course, and that end of wet season rainfall has overwhelming importance that can still be identified several months later into the dry season. For instance, in Hwange National Park (Zimbabwe), April rainfall has a positive effect on primary production extending up to July. Dry season is a bottleneck period expressing the highest constraints on savanna ecosystems, driving their carrying capacity in the long run. Savannas will be especially threatened by climate change if late wet season rainfall is to decrease, decreasing primary production and therefore resources for higher levels during the most critical period, the dry season.Savanna and tropical forest ecology; Savanna and tropical forest conservation; Landscape ecology

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CONTRIBUTION FROM THE HERD PROJECT, HWANGE ZIMBABWE, TO THE SANPARKS WORSHOP ON ELEPHANT AND BIODIVERSITY

HERVÉ FRITZ

1. We find the framework appropriate to formulate and answer questions about the effects of elephant on ecosystem functioning, and ultimately assess their role in the dynamics of biodiversity. We believe that our current research project in Hwange National Park can contribute to answering some of the questions, but comparison between large protected areas is central in assess the generality of the principles that will emerge from the workshop. The major specific contribution of Hwange to the overall debate is the semi-experiment carried out by managers (forced by circumstances though!) when the culling stopped in 1986. Today the population has reached an average density slightly below 3 ind/km² over almost 15000 km², with areas experiencing c.10 ind/km² in the dry season. Only Chobe NP has such extreme situations. Hwange elephant population seem to start showing some levelling off, hence could be one of the first populations of elephant that could be modelled including density dependence feed backs. In addition, Hwange being almost strictly driven by artificial water supplies, management issues related to boreholes, water supplies and spatial management are currently debated. Note that bush encroachment is not a major problem in Hwange, on the contrary, and elephant density certainly is one of the features that distinguish Hwange from most other parks were this is an issue (fire is not used as a management tool, and is regular but at low frequency).

2.Generally, little thorough analyses have been done on existing data sets related to management experiments (desired or accidental) of elephant populations. For instance, the Tsavo story has been crudely analysed, but the recover of the elephant population does not seem to be monitored in the light of the new questions related to diversity. We are currently analysing the Hwange story. In southern Africa, the long tradition of monitoring, and active intervention in management, have certainly created contrasted situation that need to be analysed. Comparative studies should be promoted!

Lots of concern is for instance expressed around tree diversity change, but little has been done regarding tree diversity in relation to elephant density. Most has been analysed through exclosures, which is a binary situation. Some rare tree species may in fact already disappear at very low elephant density. The large amount of data set on elephant impact on vegetation should help designing the analyses to test for the existence of frequency dependent selection of rare trees.

One of the major constraints in carrying out a “management experiment” is that movement of elephant may occur over very large areas, and therefore these experiments should be over large scales. Another key issue about scale is “at what scale do we evaluate biodiversity changes”. At a small scale, high densities of elephants will probably always have some impact, however, the heterogeneity they may create at the larger scale may promote diversity at the landscape levels. Some of the conflicting results published in the last decade on elephant-biodiversity issue may be scale dependant. It is hard to decide at what scale we should consider the question, and this should be matched with management scales (both because it is what ultimately will dictate the objective but also it sets the scales at which intervention is really feasible!). The “intermediate disturbance hypothesis – productivity” framework should be addressed explicitly when trying to set up elephant management to control their effects on biodiversity.

Disturbance culling experiment should be carried out, in order to test some spatial management of the elephant distribution. Waterhole selective access experiments are crucial for the future of protected areas relying on artificial water sources. This is particularly true regarding the fact that the public opinion would rather see some environmental manipulation than massive culling operation.

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There is a huge lack of studies on indirect impact of elephant on other species through the modification of habitat characteristics, hence change in habitat suitability. Particularly, there is little done on the changes in predation regimes associated with habitat changes.

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NUTRITIONAL REQUIREMENTS OF ELEPHANT OF PROTEIN AND ENERGY

H.H. MEISSNER

It is difficult if not impossible to measure requirements of elephant directly, but useful results can be obtained from theoretical approaches and the quality and composition of the food ingested. Using an empirical approach based on heat production, growth rates and energy values of muscle and milk, Meissner (1982) calculated a metabolizable energy requirement for adult male and non-lactating female elephant of 0.65 to 0.67 MJ kg –1 W 0.75 per day, with a 30% increase in energy demand when the female is in peak lactation. Subsequent direct measurements of food intake in various woody savanna plant communities in private reserves bordering the Kruger National Park substantiated these estimates (Meissner etal 1990). Translated into food dry matter intake these results also confirmed figures of 1.0 to 1.2% of body weight in males and non-lactating females (Foose, 1982; Owen-Smith, 1988) and 1.2 to 1.5% of body weight for lactating females (Owen-Smith, 1988).

The quality of the diet selected is normally comparatively low because of a high proportion of lignified matter. Digestibilities are also lower than expected because of fast digesta passage rates (Meissner, 1991), ranging between 30 and 50% dry matter digestibility (Meissner etal, 1990). Depending on season, crude protein may vary between 6.7% and 10.7% (Meissner etal, 1990) with an upper limit of about 15% with exclusive feeding on lush green mopane leaves or pods (Lagendijk, 2003).

These results (understanding) can be regarded as being in the category of well supported hypotheses

Food selection

Selection of grass and browse in woody savanna plant communities is dependent on season, with the wet season favouring more grass and the dry season more browse, twigs, roots and bark (De Villiers etal, 1991). The latter may increase to 60 – 98% in the dry season and in exclusive mopane savanna ( Lagendijk , 2003 ).

ReferencesDE VILLIERS, P. A. , E. W. PIETERSEN, T. A. HUGO, H.H. MEISSNER & O. B. KOK. 1991.

A method of sampling daily food selection by free-roaming elephant. S.Afr.J. Wildl. Res.21:23 – 27.

FOOSE, T.J. 1982. Trophic strategies of ruminant vs non-ruminant ungulates. Ph.D. thesis, University of Chicago.

LAGENDIJK, D.D.G. 2003. Mopane woodlands: A food source for elephants. M.Sc. Thesis Animal Ecology, Wageningen University.

MEISSNER, H.H., 1982. Theory and application of a method to calculate forage intake of wild southern African ungulates for purposes of estimating carrying capacity. S.Afr. J. Wildl. Res. 12: 41 – 47

MEISSNER, H.H., 1991. Applied aspects of digestive physiology of elephant . Pp 125 – 135 In: The African Elephant as a game ranch animal. Wildlife Group of the South African veterinary Association, Onderstepoort.

MEISSNER, H.H., E.B. SPREETH, P.A.DE VILLIERS, E.W. PIETERSEN, T.A. HUGO & B.F.TERBLANCHé. 1990. Quality of food and voluntary intake by elephant as measured by lignin index. S.Afr. J.Wildl. Res. 20: 104 – 110.

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OWEN-SMITH, N. 1988. Megaherbivores: The influence of very large body size on ecology.Cambridge University Press, Cambridge.

Management implications

The impact is on carrying capacity of elephant. Some years ago the population level (carrying capacity) of elephant in KNP was accepted as 0.4 elephant per km 2 , based on the observations/results that this level did not interfere or reduce the reproductive rate (Ebedes, 1991). This level implies some 7500 elephants in the Park.

It is interesting that if a few assumptions are made such as the average stocking rate being 10 LSU per hectare (large variation from South to North of course), while keeping grasslands from a conservation point of view at 4 tons DM per hectare and browse at one ton per hectare, and if elephant is kept at no more than one-third of the LSU’s in a balanced species composition as well as because of the limitations to the browse and woody components, from a food intake (requirement) point of view, a figure of 7000 to 8000 elephants is supported. While these figures do give some valuable pointers, the number of assumptions that have to be made indicate that we need much more information in this regard.

ReferenceEBEDES, H. 1991. Past, present and future distribution of elephants in Southern Africa. Pp 3 – 25.

In: The African Elephant as a game ranch animal. Wildlife Group of the South African Veterinary Association, Onderstepoort.

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CARBON ISOTOPIC ASSESSMENT OF THE DIETS OF ELEPHANTS IN KRUGER NATIONAL PARK – SEASONAL AND SPATIAL VARIABILITY

J. CODRON, JULIA A. LEE-THORP, M. SPONHEIMER, C.C. GRANT, D. CODRON

Introduction

Elephants are regarded as a high-impact megaherbivore species of the savanna. They are believed to have a significant effect on local habitat conditions because they can consume large amounts of woody vegetation. Indeed, calculations for elephant carrying capacity are based largely on howmuch woody plants they eat. In spite of these assumptions, however, the diet of savanna elephants remains unresolved.

Authors disagree on such fundamental questions as whether elephants are predominantly grazers or browsers. Should they be classified as either one, or are they merely mixed feeders that are influenced purely by various external factors (natural and anthropogenic) to opt for grass or woody vegetation? A thorough knowledge of why, where and when elephants choose to browse rather than graze or vice versa, is required.

Methodology

Faeces

• Elephant faecal samples were collected from the northern and southern granites and basalts, respectively, for two dry (June 2002, 2003), and two wet (January 2003, February 2004) seasons. Only recently deposited, i.e. fresh or damp, faeces were collected to avoid contamination by fungi, soil, and insects.

• Local vegetation (trees, forbs, and grasses) and faeces from browsing, grazing, and mixed-feeding (impala) herbivores was collected from various habitats (riverine, open savanna, closed woodland and thorn thickets) in different regions in KNP. This provided baseline data from which reliable interpretations about elephant diet could be made.

• Samples were oven-dried, homogenized and ground. Carbon isotope ratios ( 13C) and percent nitrogen (%N) were obtained by combusting the samples in an automated Carlo-Erba elemental analyzer and introduced via a CONFLO system to a Finnigan Mat 252 mass spectrometer. Sample 13C values were calibrated against several working laboratory standards of known isotopic composition.

• The percentage of C4 grass in each sample was estimated by assuming a diet-faeces fractionation of –0.9o/o. Isotopic “endpoint” values for C3 and C4 vegetation, specific to the region and season when the faeces were collected, were used (this enhanced the accuracy of calculations regarding estimated % C4 grass consumed).

Ivory

Sectioning of broken/damaged tusks took place immediately anterior to the pulpal cavity. With two of the tusks it was possible to remove a disc from both the “tip” (oldest growth) and “base” (most recent growth) of the tusk.

Cross sections of ivory were sampled at high resolution (1mm increments), along growth layers (starting from the core (most recent growth) and working towards the outermost rings (oldest growth)). Ivory grows continually throughout the animal’s life, and does not undergo isotopic

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turnover once dentine deposits are made. Thus, long-term dietary records are available using incremental isotopic analysis.

• To calculate estimated %C4 grass in the diet from tooth carbonate samples (such as used during ivory analysis), a diet-carbonate fractionation of ~12.5‰ is used (hence a 13C value of –14.0‰ (-26.5‰ (C3 plant average) -12.5‰ (diet-carbonate fractionation)) for elephantivory corresponds to ~100% C3 (browse) diet, whereas a 13C value of 0.0‰ (-12.5‰ (C4grass average) -12.5‰ (diet-carbonate fractionation)) represents a ~100% C4 (grass) diet.

• Five tusks representing northern, and two representing southern individuals in KNP were sampled. A third tusk representing the southern KNP was sampled at the Transvaal Museum, which came from an elephant that died in 1949. The origin of the tusk was established using the information (GPS co-ordinates and place name (Malawu (Malau) – a tributary of the N'waswitsontso River in the Satara region); Whyte, 2004 pers. comm.) on the collector’s card.

Results

Geographical and seasonal variation in elephant diet composition using faecal samples

• Northern elephants: faecal δ13C data show ~40% grass consumed during the dry season compared to ~50% in the wet season.

• Southern elephants: faecal δ13C values advocate a predominantly browse-based diet during the dry season (~10% grass consumed), and a much higher grass intake during the wet season (~50% grass).

• Elephants showed faecal N levels as low as grazers. This is probably because elephants are bulk feeders (thus incorporating a wide variety of low N food items into their diet).

• Plant %N increased from the dry to the wet season. Elephant faeces from the southern KNP paralleled the trend observed in plants. In contrast, faecal N content for northern populations remained similar during both seasons.

Discussion

Northern Kruger comprises a higher tree:grass leaf ratio (due to dominance of Colophospermum mopane) than the south. Given the dominance of mopane in the northern KNP, it was expected that elephants in this region utilize more browse than their southern counterparts. This was not the case. Accepting that Kruger elephants do not consume food in proportion to its local abundance, why do northern populations consume higher proportions of grass than those in the south?

• Selection based on nutritional value: Grasses might be preferred to woody vegetation because of their greater palatability and overall lower tannin concentrations. Woody plants contain larger quantities of indigestible compounds (such as condensed tannins and lignin).

• Avoidance of mopane: Mopane is highly abundant, and almost completely dominant amongst the woody vegetation of the northern KNP, yet completely absent from the areas south of the centrally-located Olifants River. It seems that elephants in the northern KNP utilize a relatively high proportion of grass as an alternative resource in an otherwise homogeneous, mopane-dominated, landscape. In turn, the variable, and questionable, nutritive value of mopane may further deter elephant utilization of this resource. The wider diversity of woody plant species in the southern KNP allows elephants to exploit this resource more efficiently, especially during the dry season when grass production is low.

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Variation in elephant diet composition over time using ivory samples

Results

• Ivory from south of Kruger (ZA-123-01 N’wanedzi and ZA-502-92 Tshokwane) indicates year-to-year changes in grass consumption (varying between ~15 and ~40%), but at a decadal level no major dietary changes have been noted during the last ~40 years.

• The museum specimen (TM 0046 Malawu; pre-1950) shows a diet comprising ~10 to ~40% grass, likely following a seasonal cyclical pattern. This result parallels the findings for the two more recent tusks (post 1960), as well as of the modern diet based on faecal data.

• First northern individual (ZA-0023-02 Shingwedzi): suggests a significant increase in grass consumption during the latter half of the 20th century (the onset of this is dated roughly during the late 1960’s/early 1970’s based on counting of annual ivory growth lines).

• Second and third individuals (ZA-0152-01 Letaba and ZA-0008-02 Phalaborwa): show a higher grass intake (~25-40%) than older ivory.

• Fourth northern individual (ZA-0131-89 Olifants): samples pre-date the inferred increase in grass consumption, and shows between ~10 and 25% grass in the diet, about 15% less than more recent ivory.

• Fifth individual (ZA-359-90 Vlakteplaas): shows a dietary change from less grass (~15-25%) to more grass (~25-45%), with sample dates coinciding with those of the tusk from Shingwedzi.

Discussion

• North: Combined results from ivory for 5 individuals show that elephants in the north of Kruger have started eating more grass during the last 3 or 4 decades. In addition, 20th century burning of fossil fuel has resulted in a approximate 1.5‰ depletion in the δ13C value of atmospheric CO2 between 1950 (~-7.0‰) and the present (~-8.5‰). Thus, we could have expected to find the δ13C values of ivory dated after 1950 to be lower (more negative) than they are. The fact that they are higher than they would have been before 1950 indicates that the difference in percentage grass intake since the 1960’s is even greater than results suggest.

• South: This change in diet has not been observed for the 3 individuals from the south. These findings, although only represented by a small number of individuals, parallel faecal results for 2 consecutive years.

• Faeces and ivory data both show an average 40-45% grass diet in northern elephants compared to a much lower grass intake (20-25%) in southern populations.

• A diet change during the 1960’s should also not be considered surprising, given that a number of potentially significant events took place (natural and anthropogenic) during that decade. Many of these events would have had a long-lasting effect on the KNP habitat, and hence on elephant diet (e.g. construction of artificial watering points, boundary fences, onset of culling programs, and a drought period).

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Elephants are generally expected to eat more woody plants in areas where the tree:grass leaf ratio is high, such as the mopane veld in northern KNP. Carbon isotopic data for elephant faeces show that this is clearly not the case, with elephants consuming more browse in the southern KNP than in the north, at least during the dry season. Moreover, gross dietary shifts inferred from seasonally collected faeces suggest massive variability in elephant diets within the KNP. The upshot of these findings is that carrying capacities, such as those based on a 50% grass/browse diet, are based on flawed knowledge of elephant diet. In addition, our ability to identify high-low impact zones requires further assessment. The results of this study counter-intuitively imply that impact on woody vegetation is likely to be greater in the southern KNP than in the north.

Modifications to the environment (in this case anthropogenic) may alter elephant feeding behaviour, and hence impact, on woody vegetation in poorly documented ways. The vast increase in artificial waterhole construction during the 1960’s is likely to have been one of the major engineers of increased grass consumption by northern elephant populations. Previous studies have shown that grass nutritional quality and palatability decreases with distance away from artificial watering holes. Less likely drivers of elephant diet shifts include completion of the western boundary fence during the 1960’s (and eastern fence during the 1970’s), and even the onset of culling programs towards the end of the decade. These hypotheses remain speculative, but it is nevertheless clear that feeding changes brought about by anthropogenic (or natural) causes may outweigh the importance of elephant population size in terms of their ability to alter local vegetation.

Reliability of results

Changes in habitat composition will have had an effect on elephant diet, amongst other things. For example, it has been reported that the number of tall trees (>5m) in the northern KNP have declined since the 1960’s. According to the ivory data, this time period coincides with the increase in grass consumption by northern elephants. Does this mean that elephants graze more in the absence of sufficient large trees? However, the roan camp (N’wasitshumbe) was erected in 1967 in a representative area on the northern plains, and tall trees that were present in the camp at the time are now absent too, without interference from elephants (Grant, 2004 pers. comm.). Thus, to what extent do elephants rely on tall trees, and does the number of tall trees in a given area determine how much grass an elephant eats? Given the disappearance of tall trees from the roan camp in the absence of elephant impact, it appears that there may be another environmental factor at play which drives both tree size and abundance, as well as elephant grazing habits.

Biodiversity consequences

If we consider the preliminary results of the ivory to be representative of the Kruger population, then special attention needs to be paid to the massive increase in grass consumption in the northern regions of Kruger since the 1960’s. The first facet of biodiversity impact is that a diet shift is likely linked to a change in magnitude of impact. A shift towards a more grassy diet suggests less impact on woody vegetation by elephants in the north during the last 30 or 40 years than during the first half of the 20th century. During the Kruger Science Network Meeting (April 2004), several contemporary researchers proposed bush encroachment in the KNP. Assuming that elephants are indeed major agents of landscape modification, we may then perceive that bush encroachment in northern KNP is a result, at least in part, of a shift towards a more grass-rich diet.

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Research requirements

Forthcoming data include elephant faeces collected monthly for a year from 8 different geographical regions in the Kruger Park (northern basalts, northern granites, north-central basalts, north-central granites, south-central basalts, south-central granites, southern basalts, and southern granites). To gain further information on seasonal variability in elephant diet, 19 provenanced tail hairs have been analysed serially for short-term temporal tracing. In addition, the sex of each animal from which tail hairs were removed is known, allowing for rigorous testing of sex-related dietary preferences. Thus, inferences about the dietary behaviour of male and female elephants can be made from a combination of data from faeces, tail hair, and ivory, even though the ivory specimens are only from bulls, and faeces are from both sexes (not recorded). A further 6 elephant tusks have been sampled from the Letaba Elephant Hall (and are thus well-provenanced), and analyses of those samples are currently underway.

Conclusions

Short- and long-term changes in elephant diet in different regions of KNP may have significant importance for determining the “size” of elephant impacts on woody vegetation during different seasons/decades, as well as for interpreting the responses of elephants to changes in their immediate environment.

Continuation of this study will reveal a) monthly shifts in grass/browse selection, i.e. whether north-south differences are consistent, and during which months/seasons the major shifts occur, and b) how consistent the long-term data from ivory is across several representatives of the KNP population, and what events can be linked with major diet shifts during the twentieth century (such as during the 1960s).

ReferencesCODRON, D., J. CODRON, M. SPONHEIMER, J.A. LEE-THORP, T. ROBINSON, C.C. GRANT, & D.

DE RUITER. In press. Assessing diet in savanna herbivores using stable carbon isotope ratios of feces. Koedoe .

JACHMANN, H., & R.H.V. BELL. 1985. Utilization by elephants of the Brachystegia woodlands of the Kasungu National Park, Malawi. African Journal of Ecology 23: 245-258.

KOCH, P.L. 1989. Paleobiology of the late Pleistocene mastodonts and mammoths from Southern Michigan and western New York. Ph. D Thesis, The University of Michigan.

LEE-THORP, J.A., J.C. SEALY, & N.J. VAN DER MERWE. 1989. Stable carbon isotope ratio differences between bone collagen and bone apatite, and their relationship to diet. Journal of Archaeological Science. 16: 585-599

OWEN-SMITH, R.N. 1988. Megaherbivores - The influence of very large body size on ecology. Cambridge University Press, Cambridge.

RAUBENHEIMER, E.J. 1999. Morphological aspects and composition of African elephant (Loxodonta africana) ivory. Koedoe. 42(2): 57-64.

SCHOLES, R.J., W.J. BOND, & H.C. ECKHARDT. 2003. Vegetation dynamics in the Kruger ecosystem. In: DUTOIT, J., K. ROGERS, H. BIGGS. (eds.). The Kruger Experience. Island Press, pp 242-262.

SPONHEIMER, M., T. ROBINSON, L. AYLIFFE, B. PASSEY, B. ROEDER, L. SHIPLEY, E. LOPEZ, T. CERLING, D. DEARING, & J. EHLERINGER. 2003. An experimental study of carbon-isotope fractionation between diet, hair, and feces of mammalian herbivores. Canadian Journal of Zoology81: 871-876.

VOGEL, J.C. 1978. Isotopic assessment of the dietary habits of ungulates. South African Journal of Science74: 298-301.

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CAN AFRICAN ELEPHANTS (Loxodonta africana) SURVIVE AND THRIVE IN MONOSTANDS OF Colophospermum mopane WOODLANDS?

D.D.G. LAGENDIJK, W.F. DE BOER AND S.E. VAN WIEREN

Introduction

Colophospermum mopane is an important food source for elephants during the dry season, as it is one of the few food plants still carrying leaves during this bottleneck period, and maintaining a high feeding value throughout the year. Several authors mention mopane as a bulk food for elephants, and one claims that elephants have been found feeding exclusively on mopane. Whether this is possible, in terms of energy requirements, intake and foraging time during different seasons is the focus of this study.

Methodology

This study was carried out as a literature analysis with a modelling approach. Besides the chemical composition of mopane leaves found in the literature, additional mopane leaves from Kruger National Park, South Africa (dry season: May 2002) have been analysed for nutrients and digestibility.

The energy requirements and foraging time for elephants of different sex and age categories when feeding on three mopane sources (mature green leaves (MGL), senescing leaves (SL) and twig bark (TB)) were calculated using metabolizable energy (ME) requirements (table 1).

To calculate the daily intake (kg) the ME was converted to dry matter intake incorporating digestibility and methane and urinary losses.

Results

Intakes and foraging times of elephants in different life stages during all seasons feeding on the three sources of mopane are presented in table 1.

Foraging times when feeding on senescing leaves or twig bark are under the maximum foraging times (16-18 h) for elephants in different life stages, except for lactating cows (both for 15 and 50 years of age when feeding on SCL and TB), 50 year old cows (SCL in winter, summer and autumn), 15 year old bulls (SCL in summer and autumn) and 50 year old bulls (SCL all seasons and TB in spring, summer and autumn).

Minimum intake as calculated in this study can vary between 40.5 and 257.2 kg d-1, with foraging times varying between 3:45 and 23:49 h d-1, depending on life stage, part of mopane ingested and season.

Intake from mature green leaves remains under the foraging time constraint for all life stages.

Discussion

The results derived from this study suggest that not all elephant age/sex classes can survive on mopane parts in terms of intake, as intake is usually more than the mean daily intake (4% of the live weight).

However, some notes have to be made:

- Metabolizable energy requirements are probably season dependent.

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- Only one digestibility figure for each mopane plant part is used in these calculations, while the digestibility is probably not stable throughout the year.

- The conversion rate used here to calculate forage DM to WM was 2.5 (40%). This value may fluctuate across seasons.

- The maximum intake rate calculated from the number of trunk loads per minute may vary across life stage and sex.

Nevertheless, considering the assumptions used in the model it seems very likely that elephants can indeed survive solely on mopane trees.


Mopane woodlands are characterised by low species richness. To conserve African elephants these areas must not be overlooked as the results of this study show that elephants can survive in this habitat with respect to their energy requirements. The presence of elephants might also increase the species richness of the area as elephants will coppice the mopane trees, by which feeding opportunities are created for smaller herbivores that feed on the mopane trees as well.

Reliability

The results of the calculations imply that elephants can indeed survive by feeding on mopane only, though the several assumptions incorporated in the calculations make it impossible to draw a hard conclusion whether elephants can survive on mopane only. These diverse assumptions could differ, through which it is very acceptable that elephants can survive on mopane entirely. Nevertheless, it is clear that mopane plays an important part in the feeding ecology and perhaps even in the survival of elephants during nutrient deficient periods.

Biodiversity consequences

Mopane woodlands are characterised by the relative absence of large herbivores, though elephant densities are relatively high compared to other vegetation types. Therefore, elephants can be considered a potential keystone species in mopane woodlands. Elephants coppice mopane trees, after which the tree produces multiple stems. It is known that elephants revisit earlier browsed mopane trees as regrown leaves are of better quality - higher food value and higher palatability -than leaves of unbrowsed trees. By coppicing the canopy of the trees from 10-14 m to 1.5-2 m, they secure feeding opportunities for smaller herbivores. In this way, elephants may play a role in the enhancement of the biodiversity within mopane woodlands and additionally, the biomass can play a greater role in the nutrient and energy cycling.


During this study it became clear that there are a few fields which could be explored to gain more insight in the nutrient and energy requirements of elephants and their digestive system:Mopane is ingested as bulk forage, compared to other woody plant species. Several studies only incorporated the woody plants in the diet of elephants in mopane areas, excluding the grasses and shrubs. A more extensive diet study, including these plants, as well as a chemical analysis of these species during different seasons could give more insight in the importance of mopane for elephants.

The effect of secondary compounds in elephants is an unknown territory. Mopane trees are known for their high amount of tannins, which could have a negative influence on intake, digestibility and metabolism. Therefore tannins might influence the quality of mopane as a feed, for they may reduce the availability of nutrients. However the negative effect of the mopane secondary

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compounds has not been included in this study, and could have an effect on the maximum admissible amount of mopane, which an elephant has to ingest, even when studies have shown that they can feed exclusively on mopane. As elephants ingest mopane as a bulk feed, it would be very likely that elephant use a mechanism within their digestive system which (partly) eliminates the influence of tannins on the digestive system. Herbivores can excrete proline-rich salivary compounds, which neutralise tannins and thus reduce their effects. Do elephants also have and use these salivary compounds and to what extend are the tannins neutralised?

Conclusion

Colophospermum mopane is an important food source in the diet of elephants especially during the dry season as it makes up a considerable part of the diet. The nutritive quality of mopane throughout the year is high, and the energy contents are sufficient for the survival of elephants feeding on mopane parts solely during all seasons, although ingestion apparently needs to be increased, as well as the daily foraging time in order to obtain sufficient energy from mopane.

Key publications

BEN-SHAHAR R. 1996. Do elephants over-utilize mopane woodlands in northern Botswana? Journal of Tropical Ecology 12: 505-515.

FOOSE T. J. 1982. Trophic strategies of ruminant versus nonruminant ungulates. Dissertation, University of Chicago, Chicago.

LAGENDIJK, D.D.G. 2003. Mopane woodlands: A food source for elephants. MSc thesis, Wageningen University and Research Centre, Wageningen, The Netherlands.

MEISSNER H. H. 1982. Theory and application of a method to calculate forage intake of wild southern African ungulates for purposes of estimating carrying capacity. South African Journal of Wildlife Research 12: 41-47.

STYLES C. V. & J. D. SKINNER. 1997. Seasonal variations in the quality of mopane leaves as a source of browse for mammalian herbivores. African Journal of Ecology 35: 254-265.

STYLES C. V. & J. D. SKINNER. 2000. The influence of large mammalian herbivores on growth form and utilization of mopane trees, Colophospermum mopane, in Botswana's Northern Tuli Game Reserve. African Journal of Ecology 38: 95-101.

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Table 1.Simulated seasonal intake in kg wet mass and foraging time for different sex and age categories, when feeding on three mopane sources, including percentages

in/decrease relative to mean daily intake and mean foraging time (max. 18 hMature green leaves Senescing leaves Twig bark

Weight (kg)

Mean daily WM intake 4% of live weight (kg)

ME (KJ/d) Season I

(kg WM)% relative to mean daily I

Ft (h:m)

% relative to mean Ft

I


Ft (h:m)


I


Ft (h:m)


WI 40.57 19 3:45 -79 55.96 65 5:11 -71 51.46 51 4:46 -74

SP 43.35 28 4:01 -78 53.44 57 4:57 -73 53.79 58 4:59 -72

SU 44.68 31 4:08 -77 58.96 73 5:28 -70 54.1 59 5:01 -72Calf, 5 years 850 34? 84800

AU 42.62 25 3:57 -78 58.2 71 5:23 -70 55.03 62 5:06 -72

WI 130.39 76 12:04 -33 180.82 144 16:45 -7 166.3 125 15:24 -14

SP 139.33 88 12:54 -28 172.7 133 15:59 -11 173.81 135 16:06 -11

SU 143.61 94 13:18 -26 190.53 157 17:38 -2 174.8 136 16:11 -10Cow, 15 years 1850 74 285000

AU 136.96 85 12:41 -30 188.06 154 17:25 -3 177.84 140 16:28 -9

WI 162.66 120 15:04 -16 226.07 206 20:56 16 207.92 181 19:15 7

SP 173.81 135 16:06 -11 215.92 192 20:00 11 217.32 194 20:07 12

SU 179.15 142 16:35 -8 238.22 222 22:03 23 218.55 195 20:14 12

Cow, 15 years, with calf 1850 74? 362000

AU 170.86 131 15:49 -12 235.13 218 21:46 21 222.34 200 20:35 14

WI 141.5 7 13:06 -27 194.78 48 18:02 0 179.14 36 16:35 -8

SP 151.32 15 14:01 -22 186.03 41 17:14 -4 187.24 42 17:20 -4

SU 155.84 18 14:26 -20 205.24 55 19:00 6 188.3 43 17:26 -3 Cow, 50 years 3300 132 291000

AU 148.62 13 13:46 -24 202.58 53 18:45 4 191.56 45 17:44 -1

WI 176.7 34 16:22 -9 244.15 85 22:37 26 224.54 70 20:47 16Cow, 50 years, with calf

3300 132? 375000

SP 188.8 43 17:29 -3 233.19 77 21:35 20 234.69 78 21:44 21

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Mature green leaves Senescing leaves Twig barkWeight (kg)

Mean daily WM intake 4% of live weight (kg)

ME (KJ/d) Season I


Ft (h:m)


I


Ft (h:m)


I


Ft (h:m)


SU 194.61 47 18:01 0 257.27 95 23:49 32 236.03 79 21:51 21

AU 185.6 41 17:11 -5 253.93 92 23:31 31 240.12 82 22:14 24

WI 140.01 59 12:58 -28 193.91 120 17:57 0 178.35 103 16:31 -8

SP 149.6 70 13:51 -23 185.21 110 17:09 -5 186.41 112 17:16 -4

SU 154.2 75 14:17 -21 204.34 132 18:55 5 187.47 113 17:22 -4 Bull, 15 years 2200 88 303000

AU 147.06 67 13:37 -24 201.68 129 18:40 4 190.72 117 17:40 -2

WI 151.83 3 14:04 -22 208.82 41 19:20 7 192.06 30 17:47 -1

SP 162.23 10 15:01 -17 199.44 35 18:28 3 200.74 36 18:35 3

SU 167.21 13 15:29 -14 220.04 49 20:22 13 201.88 36 18:42 4Bull, 50 years 3700 148 310000

AU 159.48 8 14:46 -18 217.19 47 20:07 12 205.38 39 19:01 6

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HISTORICAL HUMAN – ELEPHANT INTERACTIONS RELATING TO ELEPHANT POPULATIONS

CHARLES E. KAY

Introduction

According to The Kruger Experience. Stone Age people “are thought to have little impact on….natural process and [wildlife] populations” (page 3) and “population densities were so low that it is generally accepted that early humans did not shape the environment in a permanent way; rather the environment at that time shaped them [hunter-gatherers]” (page 5). Similarly, it is presumed that later Iron Age people had little impact on Kruger (pages 5-6). Unfortunately, those views are somewhat dated. Instead, I suggest the view from Nylsvlei may be more appropriate.There is a tendency among ecologists, especially if they habitually work in conserved areas, to regard people and their effect on ecosystems as an unnatural disturbance. In practice, the distinction between ‘natural’ and ‘man-made’ ecosystems is blurred and frequently arbitrary. This is particularly true of African ecosystems, which have an ancient association with humans…. The first white settlers believed that they had come into a pristine landscape, despite the fact that it was populated to varying degrees, and had been for millennia. Their attitudes persist in a nostalgic perception by the South African public of the ‘pre-colonial peiod’ as a time of undisturbed natural harmony and equilibrium. In fact, disturbances play a critical part in maintaining the structure of the vegetation. In the context of savannas, many of these disturbances are partly or wholly of human origin: burning, wood-collecting, grazing, and cultivation to name a few. The historical land-use pattern is important in that it is one of the determinants of the ecosystem as we see it now. The ‘wilderness’ landscapes of Africa are in part a consequence of centuries of human influence. [Scholes and Walker 1993:17].

It should also be noted that the densities given for “Stone Age” hunters by Freitag-Ronaldson and Foxcroft in The Kruger Experience (page 393) are nearly twice those calculated by Alroy (2001) for Paleo-Indians, who eliminated most large mammals from North and South America. You do not need many aboriginal people to have had a major impact on wildlife numbers or distribution (Kay 1994, 1995, 1997, 1998). After all, it was a very simple matter to kill elephant-sized animals. One stone-tipped spear, one dead elephant (Kay 2002) - - see Parker and Amin (1983:24-51) for a discussion of how efficiently African hunters killed elephants with poisoned arrows. In addition, aboriginal people used pit traps, weighted spears, and other assorted means including fire surrounds, to kill elephants virtually at will (Johnson et al. 1980). “The effectiveness of fire as a procurement practice cannot be minimized for…no less than 277 elephants were killed in one fire hunt alone” (Johnson et al. 1980:113).

Similary, it does not take many humans to completely alter fire and vegetation patterns. Here in the U.S., I have lightning ignition rates for every National Forest in the country, which can then be compared with potential aboriginal ignition rates. Assuming the lowest population estimate for North America above Mexico (500,000 Native Americans) and assuming that each person only lit one fire per year, you still have a potential aboriginal-ignition rate that is two times the highest know lightning-ignition rate and 350 times that of lightning-ignition rates for eastern deciduous forests, which burned frequently in the past. Using more realistic aboriginal population estimates, as well as more realistic estimates as to the number of fires started per-person per-year, potential native-ignition rates are 100 to 3,000 times that of know lightning-ignition rates. Again, the density estimates given by Freitag-Ronaldson and Foxcroft for San are nearly twice the lowest population estimates for North America, while the densities of Kruger’s Iron Age inhabitants, are 10 times the lowest North American estimate. Thus, there have been more than enough people in southern Africa to have acted as both keystone predators and the ultimate keystone species for a very long time. Clearly, there has been no wilderness in Africa for at least 100,000 years, and

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probably longer (Kay 1998). Furthermore, native people were not conservationists (Kay 1994, 1997b, 1998, 2002, 2003), as evolution by natural selection seldom favours conservation - - see LeBlanc (2003) Constant Battle: The Myth of the Peaceful, Noble Savage.

In short, conservation will only be favoured by evolution if the resource is economical to defend. For instance, if 1000 kcal are spent defending a resources, but less than 1000 kcal are derived from that resource, evolution will not favour conservation. For a variety of reasons, including competition from carnivore predators, large mammals were seldom, if ever, economical to defend (Kay 1994, 1998, 2002). Instead the logical, rational thing to do was to kill-out the large mammals as quickly as possible and then move on to other resources, which is exactly what aboriginal people did (Kay 1998, 2002). Counter-intuitively, once that was accomplished, native populations actually increased because people were forced to consume lower-ranked, but more abundant diet items (Hawkes 1991, 1992, 1993). There is also an evolved discount rate, which acts to negate a wide range of possible conservation practices (Rogers 1991, 1994).


I would like to see an in-depth discussion of the archaeological and ethnographic record not only from Kruger National Park but for a wider area as well. This should be done by people familiar with optimal foraging theory and other modern, evolutionary ecology models. A detailed, continuous-time analysis should also be conducted of all first-person historical accounts - - similar to my work in western North America (Kay 1990, 1995b, 2003; Kay et al. 2000). I have already uncovered references to aboriginal buffer zones in Africa and how elephants and other large mammals were restricted to those areas - - see Gardiner (1966: 147, 180, 226-229, 243, and 289-290) and Ford (1971: 123, 147, 153, 184-190, 231, 232, 282, 340, and 349). However, it must be remembered that even the earliest written accounts are not indicative of conditions prior to European influence because introduced diseases likely decimated aboriginal populations well in advance of actual white contact (Kay 1998, 2002, 2003; Kay and Simmons 2002).

In North America, it has been postulated that smallpox swept up from the Caribbean ca. 1520 and reduced native populations by 90% or more throughout the rest of North America before the British landed on the eastern shore of what today is the United States - - a hypothesis supported by recent archaeological work in the West (Kay 1998). I suspect that something similar happened in Africa as Arabic traders moved down the east coast. It is entirely possible that aboriginal people throughout southern Africa may have been subjected to introduced pandemics before the first European set foot at the Cape. Introduced diseases = declining aboriginal populations = less native hunting = growth of wildlife numbers - - then the first Europeans came along and described a “wilderness” untouched by the hand of man and teeming with wildlife - - this is exactly what happened in North America (Kay 1998, 2002, 2003; Kay and Simmons 2002; and references cited therein). Thus, it would be interesting to know when aboriginal people in southern Africa were first subjected to introduced diseases and the cascading trophic events those foreign agents set in motion. For as Van Aarde et al. (1999) noted, only a small percentage of an elephant population has to be killed each year to induce a declining trend and, as I have explained elsewhere (Kay 2002), due to exponential increase you can go for one million animals to nearly 60 million animals in less than 85 years once native hunting has been reduced or eliminated - - and this at a growth rate of only 5% per year - - similar to the rate of increase reported for elephant populations in various African national parks.

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I would like to submit one additional comment on SANP’s draft elephant management plan regarding the “Thresholds of Potential Concern” that would trigger various management actions. Again, I do not know how your legal system works but here in the States and Canada your TPC’s would generate a never ending series of lawsuits, as they are not specific and thus subject to interpretation. To determine if ecological integrity is being maintained in her National Parks, Canada has selected a relatively small number of parameters that can easily be quantified for each protected area. In Yellowstone and other large U.S. parks, the National Park Service has no standards, only a policy to let-nature-take-its-course, and we all know where that leads - - in other parks, however, NPS does cull overabundant herbivores. Parks Canada also culls in parks that lack predators. I also wonder where SANP is going to get the funds to adequately monitor the draft, or any other, TPC? It would be much simpler to establish elephant density standards based on a few key vegetation indicators. It must be remembered, though, that unhunted elephant populations are entirely unnatural. Moreover, it would be prudent to err on the side of the plants, for while elephant populations can recover quite quickly, it takes several hundred years to reestablish large baobabs once they are lost - - several hundred years of virtually no elephants (Whyte et al. 1996).

Finally, as noted by Whyte et al. (1996, 2003) there is no evidence that elephants were abundant in Kruger National Park over the last 1,000 years. Since elephants do so well there today, something other than food must have limited elephant numbers in the past. The only logical option is aboriginal hunting. Moreover, if elephant populations had been food-limited in the past, that species would have dwarfed as happened to megaherbivores throughout the Pleistocene when they reached oceanic islands and their predators did not (see Kay 1998 and the references cited therein).

ReferencesKAY, C. E. 1994. Aboriginal overkill: the role of Native Americans in structuring Western Ecosystems.

Human Nature 5:359-398.KAY, C. E. 1995. Pre-Columbian Human Ecology: Aboriginal hunting and burning have serious

implications for park management. Research Links: Parks Canada, Alberta and Pacific-Yukon Regions 3:20-21.

KAY, C. E. 1995. Aboriginal Overkill and Native Burning: Implications for Modern Ecosystem Management. Western Journal of Applied Forestry 10:121-126.

KAY, C. E. 1995. An alternative interpretation of the historical evidence relating to the abundance of wolves in the Yellowstone Ecosystem. Pp. 77-84 in Carbyn, L. N., Fritts, S. H. & Seip, D. R. (eds.). Ecology and Conservation of Wolves in a Changing World. Canadian Circumpolar Institute.

KAY, C. E. 1997. Aboriginal overkill and the biogeography of moose in western North America. ALCES33:141-164.

KAY, C. E. 1997. Is Aspen doomed? Journal of Forestry 95:4-11.KAY, C. E. 2002. False Gods, Ecological Myths, and Biological Reality. Pp. 238-261 in Kay, C. E. &

Simmons, R. T. (eds.). Wilderness and political ecology: aboriginal influences and the original state of nature. The University of Utah Press.

KAY, C. E. Lewis and Clark, Aboriginal Overkill, and the Myth of Once Abundant Wildlife. 103-109. 2003. Missoula, The University of Montana Printing & Graphic Services.

MANN, C. C. 1491. The Atlantic Monthly 289(3), 41-53. 2002. THOMSON, R. 2003. A Game Warden's Report. Magron Publishers.WHITE, C. A., LANGEMANN, E. G., CORMACK GATES, C., KAY, C. E., SHURY, T. & HURD, T. E.

Plains Bison restoration in the Canadian Rocky Mountains? Ecological and management cosiderations. Harmon, D. 152-160. 2001. The George Wright Society, Inc.

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ECOSYSTEM RESOURCES INFLUENCING ELEPHANT POPULATIONS

NORMAN OWEN-SMITH

Kruger Parks elephant population is currently in a phase of exponential population growth. A fundamental principle in population dynamics is that as populations increase, resource limitations lead to a decline in birth rates and/or an increase in death rates, until at some stage the net population growth rate becomes zero. The density level at which this occurs is conventionally labelled K carrying capacity. The uncertainty is how these changes occur. It seems that, for very large, long-lived mammals, changes in birth and death rates occur quite close to the carrying capacity level. Furthermore, through vegetation impacts, the approach to carrying capacity rather than being smooth could involve oscillations between the herbivore population and vegetation resources. The possibility that such oscillations could become extreme, especially in fenced areas where dispersal is prevented, raises concerns about the consequences for biodiversity.

For megaherbivores like elephants a lengthening of the interval between births, reduction in juvenile survival, and shift in the population structure towards older animals are the prime processes restricting population growth. Little change in mortality among prime-aged adults is expected except episodically during extreme droughts. Evidence from Botswana indicates that predation by lions on young animals after high local densities have been reached may contribute importantly towards slowing population growth.

Emigration elsewhere could alleviate extreme vegetation impacts during severe drought periods, provided space for such movements is available. True dispersal involves the abandonment of previously established home ranges and the occupation of new areas. Local re-distribution within the home range, or expansion of movements beyond the normal home range, will also affect the spatial distribution of impacts on vegetation. Theory plus supporting observations on other species suggests that buffer resources low in quality but able to provide some sustenance during critical periods can dampen severe population crashes.

Water distribution can also have an important influence on population processes by restricting access to vegetation components or landscape regions. Areas too remote from water to be accessed during severe droughts escape severe impacts during these times. Through crowding around remaining water sources density effects are accentuated, including loss of feeding time, physiological drains from travel, and increased exposure to predation. Obviously the vegetation near perennial water will incur severe impacts, with the plant species persisting being those that can tolerate, resist or avoid these impacts. These are the processes that probably halted population growth by elephants in past times. The wider the water distribution, the more extensive the severe vegetation impacts, and the larger the population at the stage when increase is halted. This is obviously a source of concern in Kruger with its widespread water availability, both artificial and natural.


Past debates on elephant management have placed too much emphasis on numbers. More attention needs to be given to the distribution of the population and hence the effective densities and impacts experienced by the vegetation. In northern Botswana, the regional density is only 1 elephant per km2, but local dry season concentrations reach 6 per km2 along the Chobe River and over 20 per km2 along the Linyanti River. The wet season distribution of this population is also highly uneven.

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Because severe impacts are localised, scientific studies have failed to establish any general concern for biodiversity, despite a population size vastly greater than that in Kruger.

Placing an arbitrary ceiling on the population through culling during the exponential growth phase is a crude and poorly targeted way to manage the situation. The aim should be to allow the population to move towards density levels where natural processes slow the rate of population growth. Managers are concerned that if the population grew much larger than its current level, it would be practically difficult to remove the surplus. This assumes that exponential growth continues indefinitely. A population twice the size but growing at half the rate would produce the same surplus, should removals be justified.

Furthermore, a disproportionate share of the severe damage to trees is due to mature males. The spatial distribution of such damage should be managed by disturbance culling to restrict the use of sensitive areas by the mature male segment, plus the removal of all artificial water sources from such regions. More broadly, the management aim should be to accentuate spatio-temporal heterogeneity in the distribution of elephants rather than placing some arbitrary and hence contentious density ceiling. This could be done by restricting the distribution of the elephants during the times of the year when they are most dependent on woody vegetation. The densest concentrations should be in vegetation types best able to resist severe damage, or needing opening where thickets have developed. Adjusting surface water availability could contribute towards this, while limited disturbance culling assisting where necessary.

Ecologically enlightened management of the elephant population and its impacts on vegetation would not be difficult to achieve, even within the fenced confines of the Kruger Park. The major problems will be social ones with neighbouring people in a situation where an elephant population confined within a fenced area experiences periodic food limitations. Break-outs through fences are likely to result with consequent havoc to adjoining agricultural activities. Hence the main justification for culling will be to restrict elephant abundance levels in boundary regions where fences are vulnerable or subject to disruption during floods, such as along the Crocodile River in the south. Managers of private wildlife reserves adjoining the Kruger Park in the west will have to deal with such problems. On private or communal land elephants can be hunted, culled or otherwise disposed of. There may be little justification for culling elephants throughout the vast central region of the Kruger Park.

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SUMMARY AND CONCLUSIONS

NORMAN OWEN-SMITH

The knowledge base

Vital rates

Populations cannot continue growing indefinitely. Eventually resource limitations or other density-dependent effects lead to a decline in birth rates and/or an increase in death rates, until at some stage the net population growth rate becomes zero. The zero growth level is termed K carrying capacity, from the logistic equation describing this pattern. Whether environmental resources can sustain this density in the long term is a different interpretation of the carrying capacity concept.

The general pattern for large mammals is firstly a reduction in juvenile survival, followed by reduced fertility expressed largely as a reduction in age at first reproduction, and only at a late stage a lowering of survival among prime-aged females. Much of the change in overall adultsurvival may be due largely to a shift in the age structure towards older animals with reduced survival rates as a consequence of declining recruitment. For very large mammals subject to little or no predation, changes in survival rates may occur only at a late stage in population growth.

Hence for elephants and other megaherbivores, a delay in age at first parturition and lengthened birth intervals are likely to be the first manifestations of density dependence. At a later stage an increase in mortality among calves is likely to become more influential. The inherent growth rate averaging 6.6% per year manifested by the Kruger Park elephants recently (subtracting culling removals; Whyte 2001) is close to the upper limit possible for an elephant population (Owen-Smith 1988, Calef 1988). Smuts (1975) reported a mean birth interval of 4.5 years between 1968 and 1974 from placental scars, but using individual animal observations Whyte (2001) found the mean calving interval to be 3.7 years between 1976 and 1995, close to the lowest limit documented in studies elsewhere. A 7% annual population growth can be generated by a demographically structured model incorporating the following assumptions: first calving at 11 years; 3.8 year mean birth interval; 5% infant loss during the first year; 1% annual mortality up to 5 years of age; and 0.5% mortality among females thereafter (slightly higher mortality was allowed among males). The Addo elephant population increased at 5.5% per year to attain a density of 2.8 animals per km2 by 1998. This growth rate was associated with a 3.8 year mean birth interval, mean age at first calving of 13 years, mortality loss of 6% of calves during the first year, and annual mortality thereafter 1.8% (Whitehouse & Hall-Martin 2000). In Amboseli the mean age at first calving was 14 years, mean birth interval 4.5 years, juvenile survival until 5 years of age averaged 97% per year, and survival thereafter averaged 98.5% per year (with two-thirds of the mortality human-caused; Moss 2001). Male elephants showed higher mortality rates than females at all ages. These vital rates were associated with a population increase rate averaging 3.75% per year after 1979, at a density level of around 2 elephants per km2. A recent assessment for Tsavo East population indicated first calving at 15+ years and a birth interval of 5.0 years (McNight 2000). This reproductive pattern would lower the population growth rate to around 3.5% per year, i.e. half the maximum, even if mortality losses remained at their assumed minima. Quadrupling mortality, i.e. infant losses to 20% and adult mortality to 2% per year, reduces this population growth rate to just over 1% per year. Thus light culling at this rate would be sufficient to halt population growth. Leggatt (submitted report) states

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that the elephant population in western Namibia appeared stable with a mean birth interval of 5 years and age at first calving varying between 11 and 20 years, but some emigration was taking place.

The survival of young elephants up to 12 years age appears positively related to rainfall in the year of birth (van Aarde et al. manuscript). This raises the potential for “cohort effects” whereby conditions around birth affect the fecundity and survival of animals for the remainder of the lives. The implication is that elephants born under generally favourable conditions may be more resistant to adverse conditions than elephants born during more crowded circumstances.

Range compression can heighten density effects and even lead to a declining population trend, achieved largely through reproductive delays (Laws, Parker & Johnstone 1975). Compression precipitated the notorious die-off of at least 6000 elephants, or 15% of the population, in Tsavo East during an extreme drought over 1970-71. Most of these deaths occurred in the region where the annual rainfall was under 200 mm during this period, and there was little change in mortality in Tsavo West where rainfall remained higher. Drought-related mortality amounted to 5-9% of the population in Hwange during 1994, mostly among juveniles, but continuing mortality during 1995 included many adults (Dudley et al. 2001). Leggatt (submitted report) states that all calves less than 8 years of age died during this period, with most foetuses also aborted. Episodic severe losses like these mean that annual mortality rates over short periods do not reliably indicate the effective mortality losses over extended periods. Generally little mortality can be ascribed to disease, except in Etosha where endemic anthrax seem to be limiting the population growth. While fire has been responsible for some elephant deaths in Kruger, the numbers involved seem inconsequential (Whyte, submitted report).

A complication for population models is that feeding and breakage by large herbivores results in a change in vegetation state, thereby altering the capacity of the food resource to support the population. The delays inherent in this interaction can lead to oscillations or even persistent cycling in abundance, especially in a homogeneous environment (Caughley 1976). More sophisticated models suggest that the oscillatory tendency can be dampened or suppressed by appropriate functional heterogeneity in resources (Owen-Smith 2002a, 2005). Furthermore, herbivore impacts tend to be concentrated in “key resource” areas during critical periods of the year, with little impact on the remainder of the vegetation during the rest of the year (Illius & O’Connor 1999). This can generate feedback effects on the dynamics of the herbivore population despite environmental variability (Illius & O’Connor 2000). Positive feedback effects can enhance the productive capacity of the vegetation by promoting grazing lawns or equivalent shrubby stages of woody vegetation. Nevertheless, the low carryover of biomass into the dry season in such stands means that they need to supported by lower-quality reserve or buffer resources elsewhere, otherwise animals starve rapidly (Owen-Smith 2002b).

Predation by lions on young elephants, documented in Central African Republic (Ruggiero 1991), has become a substantial cause of mortality among elephants up to 15 years of age in northern Botswana (Dereck Joubert unpublished manuscript) and Hwange (anecdotal reports), seemingly accentuated by crowding around waterpoints. Its effect on juvenile survival rates has not been quantified.

The importance of dispersal movements, or at least population re-distribution, in regulating local elephant densities has been demonstrated in East Africa (Laws, Parker & Johnstone 1975). The northern Botswana population is currently expanding its range both within Botswana and through neighbouring countries. Further evidence of dispersal is provided by the initial colonisation of Kruger by elephants, and the influx of elephants into adjoining private nature reserves after the removal of Kruger’s western boundary fence (van Aarde et al. manuscript).

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Water

Elephants generally drink every 1-2 days, and hence are restricted to a maximum movement range of 16 km from water during the dry season (Conybeare 1991). Modal distances from water during the dry season were 2-6 km for females and with 4-10 km for males in Hwange and Chobe (Stokke & du Toit 2002). Seasonal concentrations reach well over 7 elephants per km2 near the Kwando and Linyanti Rivers in northern Botswana, although only for perhaps 6-8 weeks. Local elephant densities along the Chobe River are 4 animals per km2 during the dry season, dropping to 0.5 per km2 during the wet season when many elephants disperse inland (Gibson et al. 1998).

Food

Elephants are mixed feeders, with their diet consisting largely of grass during the wet season and woody browse during the dry season. Much of the woody plant material consumed is in the form of bark from branchlets (Owen-Smith 1988). Wide regional variation in the proportion of grass relative to browse has been recorded, from over 95% grass year-round in Murchison Falls, Uganda (Field 1971) to over 90% browse during the dry season in Ruaha, Tanzania (Barnes 1982). Most feeding on woody plants occurs within a height range of 2-4 m. De-barking large trees and digging for roots occur mainly during the late dry season when little foliage remains, and these fibrous parts serve as buffer resources during severe droughts. However, at certain times elephants discard leaves and consume just bark from branch tips. They also uproot and consume underground parts of grass tufts. Elephants can be narrowly selective for woody species at times, e.g. just three shrub species contributed most of the food consumed near the Chobe River seasonally (Chafota in preparation). Some tree felling seems clearly related to the lack of more readily accessible food following burning or frosting of the shrub layer (Chafota, in preparation). Favoured or staple genera of woody plants include Acacia, Colophospermum, Grewia, Baphia, Bauhinia, Combretum and Terminalia. Genera avoided or neglected include Boscia, Capparis and Croton.

Using carbon isotope assessment, Codron et al (MS) found that grass consumption by elephants had increased from around 20% to about 40% during the dry season over the past 30 years in northern Kruger, while the grass proportion during the dry season had remained consistent at about 10% in southern Kruger. In private nature reserves adjoining central Kruger, the dietary proportion of graminoids was about 20% during the dry season (Greyling 2004). Lagendijk (submited report) suggests that a diet consisting entirely of mopane would be adequate nutritionally for elephants during the dry season. Elephant diets during the Pleistocene 5-1 million years ago, as indicated by isotope ratios, show a much greater predominance of C4 over C3 plants than generally observed today (Cerling et al. 1999).

Daily food requirements amount to about 1.0-1.2% (dry mass) of body mass per day for mature males and non-reproductive females and 1.2-1.5% of body mass per day for lactating females. In Timbavati the crude protein content of the wet season diet averaged 10.7% of dry mass and the dry season diet 6.7%, while the dry matter digestibility ranged between 30-45%, for males (Meissner et al. 1990). Males consume a greater proportion of roots and other woody tissues than females, and fell trees 3-5X more frequently than females (Guy 1976; Stokke & du Toit 2000). Considering the digestive inefficiency of African elephants, coupled with dentition adapted for a mixed diet, it seems unlikely that a purely grass diet year-round would support a positive population growth.

Density limitations

Elephants formerly attained regional densities exceeding 3 animals per km2 in northern Uganda and Luangwa Valley in Zambia, and populations have continued to grow at density levels over 2

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animals per km2 in Hwange and Amboseli (Owen-Smith 1988). Hence Kruger could potentially harbour over 50 000 elephants, unless surface water restricted their distribution.

Home ranges of elephants average 880 km2 in Kruger, but with wide individual variation (Whyte 2001). Bull elephants and family units tend to concentrate in different regions (MacFadyen submitted report). During the late dry season family units tend to occur near larger rivers, while bulls remain more widely dispersed, perhaps relying more on artificial water sources. There is little clarity yet on how water or nutrients control home range extents, or selective utilization ofresources and habitats within these home ranges at different times (Krishnamoorthy et al. submitted report; Grainger et al.?; Slotow submitted report;.van Aarde et al manuscript). However, highest local densities in Kruger approaching 1 per km2 occur within mopane bush savanna and forest landscapes (MacFadyen submitted report)

Whyte (2001b) assembled evidence suggesting that elephant numbers in the lowveld region were vastly lower in the past than shown in Kruger today, from rock paintings, baobab scars and writings of early travellers. They may well have been low during the 19th and earlier centuries because of the extensive ivory trade funnelled through the nearby ports. Ivory exports through Delagoa Bay approached 50,000 kg per year in the late 1780s, probably carried from the interior by slaves as well as further north in Africa through this period (Eldredge in Hamilton 1995). However, from the abundance of the trade elephants must have been very common through the region prior to this time.

Cumming (pers. comm.) contends that human predation, by both stone age and iron age people before the advent of fire-arms, held elephant abundance levels well below those being attained today. Kay (submitted report) extrapolates the huge impact that early humans had on large herbivores across North America to support a similar view. However, archeological evidence documents only sporadic hunting of elephants by stone age cultures in Africa. Klein (1977) states specifically for southern Africa that “Middle Stone Age sites suggest a common hunting pattern preying on medium to large ungulates and generally avoiding both large carnivores and the largest, most dangerous herbivores (rhinos and elephants)” and that “Late Stone Age people concentrated their hunting on various ungulates up to buffalo size and largely ignored or avoided elephants”. Relationships between early humans and large mammals were somewhat different in Africa than elsewhere for a number of reasons, as outlined by Owen-Smith (1987, 1988). Clearly the ivory trade depleted elephants across a vast region of Africa, perhaps from as early as 1200 AD onwards (Reader ). Nevertheless European hunters and travellers found that elephants remained abundant in northern KwaZulu (Baldwin 1863, Delagorge) and through much of Zimbabwe (Selous ) in the early 19th century, alongside pastoral people. Circumstances under which a predator can hold a prey population well below the food ceiling are quite narrow, and unlikely to be fulfilled by humans as predators, although human killing could lead to local extirpation where hunting was persistent.

A major uncertainty is what the state of the vegetation will be at the stage when density feedbacks reduce the growth rate of the elephant population to zero. If further population increase is halted solely through food limitation, the vegetation is likely to be severely altered; or more specifically, those components favoured by elephants are likely to be severely depressed in the regions serving as key resource areas during critical periods. Hence the relevant issue is not on the severity of vegetation impacts by elephants, but their extent. Woodland elimination could occur locally in regions with fertile soils where woody species are mostly palatable, but is unlikely in infertile areas where unpalatable species would assume predominance. Furthermore, severe woodland clearing would not be expected in areas remote from water because elephants are most dependent on the woody plant component during the dry season when their distribution becomes limited by surface water. Moreover, woodland elimination would be difficult in riparian woodlands where many tree

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species have deep roots to access subsoil water. A disproportionate share of woodland damage is due to mature males, so that their distribution largely governs where woodland changes would be most severe.

While dispersal movements are constrained by fences, there is scope for spatial re-distribution within home ranges, in response to temporal variability in the availability of water as well as in the attractions provided by particular food resources (van Aarde et al. manuscript). Adaptive behaviour in response to spatio-temporal variability in habitat conditions could alleviate the severity of the impacts on any particular vegetation component (Owen-Smith 2002b).

Implications for further research and management

Holding Kruger’s elephant population at an exponential phase of population growth is not defensible ecologically. The early motivation was justified as a precautionary holding response until further information accrued. Current support for placing a low ceiling on the elephant population seems to be a legacy of the command-and-control management of the past, on the basis that if the elephant population was much larger it would become practically difficult to halt the increase by removing the surplus. This overlooks the inevitability that the net population growth rate will decrease as resource limitations become effective. Nevertheless, there are valid concerns about how smoothly or wildly the resource limitations will take effect in circumstances where the potential for dispersal before extreme thresholds of vegetation recovery are surpassed is restricted by boundary fences and human settlements.

There is no clear ecological justification for capping the elephant population at its current level, or not much higher, except as a precautionary measure. On the other hand, there are risks associated with allowing the elephant population to grow to the food ceiling, recognising the high density levels likely to prevail at this stage. The extent to which spatial heterogeneity in vegetation and water distribution could maintain biological diversity even within the vast area of Kruger is uncertain. Targeted interventions will be needed to ensure that the mandate of biodiversity conservation is met, and also to address the wider ramifications of vastly elevated elephant densities for human activities in adjoining areas.

The currently formulated zones provide a starting framework. However they are currently defined in terms of permissible elephant density trends rather that being targeted on the consequences of particular density levels for biodiversity. Why is there a differentiation between botanical reserves and low impact zones? To what extent are these regions appropriate, and adequate, for protecting threatened components of the biota? In what circumstances might intervention be justified even within the high density zones? Have adequate temporal periods of response been allowed in formulating currently defined “thresholds of potential concern”? What other forms of intervention, besides blanket culling, might be effective in restricting impacts on sensitive plant species, vegetation types and habitat structures?

Furthermore it might be appropriate be to accentuate density concentrations of elephants at critical times of the year, within regions best able to endure severe impacts, in order to heighten density feedbacks restricting population growth through the key resources principle. An obvious procedure would entail restricting waterpoint distribution. The further females and young have to travel between water and feeding areas where adequate food remains, the greater the stress on the survival of the offspring. Following the closure to date of 184 artificial waterpoints, 37% of the park area is now further than 8 km of surface water during the late dry season (van Aarde et al. manuscript). How effective will this be in increasing the stress on elephants especially during severe drought periods?

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A basic uncertainty concerns factors governing the distribution of elephants across habitat types and in relation to vegetation and water resources at different times of the year. Impacts on woody vegetation depend directly on where the elephants are at crucial periods of the dry season. A second key uncertainty concerns the conditions under which density effects start to have a substantial effect on reproductive and mortality rates. Further research on population attributes and vital rates needs to be directed towards these questions.

There is one striking omission in the overall workshop structure: there is no section addressing processes in savanna tree populations. The biodiversity consequences of increasing elephant numbers depends on how, when and where mature trees killed by elephants are replaced through regeneration. This is the crux of whether the impacts of elephants as predators heightening tree mortality are sustainable.

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Documents

Carbon Isotopic Assessment OF THE Diets OF Elephants IN Kruger National Park–Seasonal AND Spatial Variability