Vocal recognition in the spotted hyaena and its possible implications regarding the evolution of intelligence

Spotted hyaenas, Crocuta crocuta, are gregarious carnivores whose social lives share much in common with those of cercopithecine primates. We conducted playback experiments to determine whether free-living hyaenas are capable of identifying individual conspecifics on the basis of their long-distance vocalization, the 'whoop'. When prerecorded cub whoops were played to mothers and other breeding females (controls), mothers responded significantly more vigorously to whoops of their own cubs than did controls. We also tested the hypothesis that specific vocal recognition abilities are based on kinship in this species. Listeners that were related to the whooping cub responded more vigorously to recorded vocalizations than did unrelated individuals, with response intensity in some cases increasing directly with the size of the coefficient of relatedness (r). Our final goal was to determine whether control animals in these experiments can recognize third-party social relationships among other group members, an ability demonstrated by vervet monkeys, Cercopithecus aethiops, in similar playback experiments conducted by earlier investigators. In contrast to vervets, control females in the present experiments were no more likely to look at the mother of the whooping cub than at other control females after playback. This suggests that hyaenas may accomplish many of the same social feats as do vervets without possessing the ability to recognize third-party relationships. If confirmed in other domains of hyaena social life, our findings have important implications regarding selection pressures favouring the evolution of intelligence. (C) 1999 The Association for the Study Animal Behaviour.