COMMUNAL HUNTING AND PACK SIZE IN AFRICAN WILD DOGS, LYCAON-PICTUS

African wild dogs are 20-25 kg social carnivores whose major prey are ungulates ranging from 15 to 200 kg. In the Selous Game Reserve, Tanzania, wild dog pack size ranged from three to 20 adults (3-44 including yearlings and pups). Data from 905 hunts and 404 kills showed that hunting success, prey mass and the probability of multiple kills increased with number of adults. Chase distance decreased with number of adults. None the less, the distribution of per capita food intake across adult pack size was U-shaped, with a minimum close to the modal pack size. A similar result has been used to conclude that cooperative hunting does not favour sociality in lions (Packer et al. 1990, Am. Nat., 136, 1-19), and to argue that cooperative hunting is not responsible for group living in any carnivore (Care 1994, Cheetahs of the Serengeti Plains: Group Living in an Asocial Species). Daily per capita food intake only accounts for variation in the benefits to cooperative hunting, ignoring variation in costs. For Selous wild dogs, per capita food intake per km chased peaked close to the modal adult pack size (where per capita food intake per day was near its minimum). Thus, the energetics of cooperative hunting favour sociality in Selous wild dogs. Analyses that incorporate Variation in both costs and benefits of hunting may show that cooperative hunting favours sociality in other species where its influence has previously been rejected. (C) 1995 The Association for the Study of Animal Behaviour