Population and individual elephant response to a catastrophic fire in Pilanesberg National Park.
In predator-free large herbivore populations, where density-dependent feedbacks occur at the limit where forage resources can no longer support the population, environmental catastrophes may play a significant role in population regulation. The potential role of fire as a stochastic mass-mortality event limiting these populations is poorly understood, so too the behavioural and physiological responses of the affected animals to this type of large disturbance event. During September 2005, a wildfire resulted in mortality of 29 (18% population mortality) and injury to 18, African elephants in Pilanesberg National Park, South Africa. We examined movement and herd association patterns of six GPS-collared breeding herds, and evaluated population physiological response through faecal glucocorticoid metabolite (stress) levels. We investigated population size, structure and projected growth rates using a simulation model. After an initial flight response post-fire, severely injured breeding herds reduced daily displacement with increased daily variability, reduced home range size, spent more time in non-tourist areas and associated less with other herds. Uninjured, or less severely injured, breeding herds also shifted into non-tourist areas post-fire, but in contrast, increased displacement rate (both mean and variability), did not adjust home range size and formed larger herds post-fire. Adult cow stress hormone levels increased significantly post-fire, whereas juvenile and adult bull stress levels did not change significantly. Most mortality occurred to the juvenile age class causing a change in post-fire population age structure. Projected population growth rate remained unchanged at 6.5% p.a., and at current fecundity levels, the population would reach its previous level three to four years post-fire. The natural mortality patterns seen in elephant populations during stochastic events, such as droughts, follows that of the classic mortality pattern seen in predator-free large ungulate populations, i.e. mainly involving juveniles. Fire therefore functions in a similar manner to other environmental catastrophes and may be a natural mechanism contributing to population limitation. Welfare concerns of arson fires, burning during "hot-fire" conditions and the conservation implications of fire suppression (i.e. removal of a potential contributing factor to natural population regulation) should be integrated into fire management strategies for conservation areas.
Woolley
Leigh-Ann
LA
Amarula Elephant Research Programme, School of Biological and Conservation Sciences, University of KwaZulu-Natal, Durban, South Africa. leigh-ann@polka.co.za
Millspaugh
Joshua J
JJ
Woods
Rami J
RJ
van Rensburg
Samantha Janse
SJ
Mackey
Robin L
RL
Page
Bruce
B
Slotow
Rob
R
D000818:Animals; D001315:Australia; D001522:Behavior, Animal; D004606:Elephants / Q000502:physiology*; D004777:Environment; D005260:Female; D005390:Fires; D005938:Glucocorticoids / Q000378:metabolism; D006728:Hormones / Q000378:metabolism; D008297:Male; D015233:Models, Statistical; D011336:Probability; D013997:Time Factors; D014197:Trees
D005938:Glucocorticoids; D006728:Hormones
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