African ungulates and their drinking problems: hunting and predation risks constrain access to water

Prey make several behavioural adjustments to minimize the risk of predation by their natural predators. When hunted, however, they may have to adjust their behaviour further or differently to cope with this additional mortality risk. Here, we investigated whether African large ungulates would adjust their behaviour in response to hunting risk (i.e. risk of being shot by human hunters). We predicted that they would shift their use of surface water, a key and scarce resource in African savannas, from day hours to night hours to reduce the risk of encountering human hunters. In Hwange National Park, Zimbabwe, we monitored waterholes to record the temporal drinking niche of three nonhunted ungulates (i.e. impala, Aepyceros melampus, greater kudu, Tragelaphus strepsiceros, sable antelope, Hippotragus niger). We also monitored waterholes in hunting areas in the vicinity of Hwange National Park. In Hwange National Park, the three species avoided waterholes at night, when the risk of natural predation was higher. Conversely, in the hunting areas, all three species visited waterholes more often at night. Impala and greater kudu, however, were less prone to switch towards night-time use of waterholes in hunting areas compared to sable antelope, although all three species were exposed to similar hunting risk. Our results suggest that hunting may force African ungulates to shift their visits at waterholes from day hours towards night hours, but that the magnitude of this shift may be constrained by the predation risk imposed by large nocturnal carnivores. We conclude that species preyed upon by natural predators adjust their antipredator behaviour in response to the additional risk of predation imposed by hunting.