Brains, brawn and sociality: a hyaena's tale

Holekamp, K.E., Dantzer, B., Stricker, G.M., Shaw, Yoshida K.C., and Benson-Amram, S.



Invited paper for a special issue on "How the Evolution of Sociality Shapes the Brain, Behavior and Cognition."

Theoretically intelligence should evolve to help animals solve specific types of problems posed by the
environment, but it remains unclear how environmental complexity or novelty facilitates the evolutionary
enhancement of cognitive abilities, or whether domain-general intelligence can evolve in
response to domain-specific selection pressures. The social complexity hypothesis, which posits that
intelligence evolved to cope with the labile behaviour of conspecific group-mates, has been strongly
supported by work on the sociocognitive abilities of primates and other animals. Here we review the
remarkable convergence in social complexity between cercopithecine primates and spotted hyaenas, and
describe our tests of predictions of the social complexity hypothesis in regard to both cognition and brain
size in hyaenas. Behavioural data indicate that there has been remarkable convergence between primates
and hyaenas with respect to their abilities in the domain of social cognition. Furthermore, within the
family Hyaenidae, our data suggest that social complexity might have contributed to enlargement of the
frontal cortex. However, social complexity failed to predict either brain volume or frontal cortex volume
in a larger array of mammalian carnivores. To address the question of whether or not social complexity
might be able to explain the evolution of domain-general intelligence as well as social cognition in
particular, we presented simple puzzle boxes, baited with food and scaled to accommodate body size, to
members of 39 carnivore species housed in zoos and found that species with larger brains relative to
their body mass were more innovative and more successful at opening the boxes. However, social
complexity failed to predict success in solving this problem. Overall our work suggests that, although
social complexity enhances social cognition, there are no unambiguous causal links between social
complexity and either brain size or performance in problem-solving tasks outside the social domain in
mammalian carnivores.

Animal Behavior, 103, 237-248
Holekamp, K.E., Dantzer, B., Stricker, G.M., Shaw, Yoshida K.C., and Benson-Amram, S. 2015. Brains, brawn and sociality: a hyena’s tale. Animal Behaviour, 103, 237-248.