Vulnerability to predation and water constraints limit behavioural adjustments of ungulates in response to hunting risk

The magnitude of behavioural adjustments by prey in response to predation risk is constrained by the necessity to maintain resource acquisition. In systems with high predation risk, prey display adjustments that can challenge resource acquisition. In such cases, prey may be limited in their ability to adjust their behaviour further in response to additional risk, such as that posed by human hunters (hunting risk). We investigated whether large African herbivores adjust their behaviour in response to hunting risk. In Hwange National Park (HNP), Zimbabwe, and in the peripheral hunting areas (HA), we monitored behaviour of impala, Aepyceros melampus, greater kudu, Tragelaphus strepsiceros, and sable antelope, Hippotragus niger, at waterholes. Once groups entered waterhole areas, their probability of returning to vegetation cover without drinking was higher in HA than in HNP. Individuals were more vigilant in HA than in HNP when they were approaching and leaving waterholes, but not during drinking. This suggests that drinking was prioritized over vigilance once individuals reached waterholes. The time that groups spent in waterhole areas did not differ significantly between HA and HNP, but individuals in HA were more vigilant, suggesting that groups limited their exposure to hunters. Greater kudus were the most vigilant, probably because they are the most vulnerable to predators. Sable antelopes were the least prone to compromise the acquisition of surface water. Both species consequently displayed adjustments of lower magnitude than impala in response to hunting risk. Our multispecies study illustrates how vulnerability to natural predators and environmental constraints limit behavioural responses of large herbivores to hunting risk. (c) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.