Social intelligence in the spotted hyena (Crocuta crocuta)

Abstract

If the large brains and great intelligence characteristic of primates were favoured by selection pressures associated with life in complex societies, then cognitive abilities and nervous systems with primate-like attributes should have evolved convergently in non-primate mammals living in large, elaborate societies in which social dexterity enhances individual fitness. The societies of spotted hyenas are remarkably like those of cercopithecine primates with respect to size, structure and patterns of competition and cooperation. These similarities set an ideal stage for comparative analysis of social intelligence and nervous system organization. As in cercopithecine primates, spotted hyenas use multiple sensory modalities to recognize their kin and other conspecifics as individuals, they recognize third-party kin and rank relationships among their clan mates, and they use this knowledge adaptively during social decision making. However, hyenas appear to rely more intensively than primates on social facilitation and simple rules of thumb in social decision making. No evidence to date suggests that hyenas are capable of true imitation. Finally, it appears that the gross anatomy of the brain in spotted hyenas might resemble that in primates with respect to expansion of frontal cortex, presumed to be involved in the mediation of social behaviour.

Figure 1

Dorsal views of the cerebral hemispheres of four carnivore species. The yellow box indicates the approximate area of the frontal cortex, defined as the cortex rostral to the cruciate sulcus (cs). Note the relative volume differences among the species. The relative amount of frontal cortex appears greatest in dog and spotted hyena. Other abbreviations: PR, proreal gyrus; prs, presylvian sulcus; psd, post-cruciate dimple. Whole brain images from the University of Wisconsin Comparative Mammalian Brain Collections (supported by the National Science Foundation) at http://www.brainmuseum.org.

Figure 2

Rendering of CT images from an adult female spotted hyena skull showing both the skull and virtual brain endocast (arrow).