Zoology: Chimpanzee behavioural diversity higher in groups from variable environments

Chimpanzee groups that live in environments with greater historical and current variability develop a more diverse repertoire of behaviours than those from more stable environments. The study of data from 144 wild chimpanzee communities, published this week in Nature Communications, suggests that environmental variability was a factor in promoting the behavioural, as well as cultural diversification of great apes.

The environment a species or population inhabits can shape the behavioural and cultural traits that it develops. For example, having a broader range of behaviours could help species cope with environmental variability over time. Ammie Kalan and colleagues tested this relationship using a database of 31 chimpanzee behaviours at the population level; the behaviours ranged from cave use and bathing to foraging strategies and tool use. The authors analyzed whether the use of certain behaviours by 144 chimpanzee groups was related to three different measures of environmental variability across different timescales: variability in rainfall, use of savannah versus forest habitat, and the distance from glacial forest refuges.

The results show that chimpanzee populations living further away from locations that were forest refuges during glacial cycles in the Pleistocene (approximately 2.5 million to 10,000 years ago) had more diverse behavioural repertoires. The authors suggest that the populations that moved away from refuges over time may have been more likely to innovate new types of cultural behaviours than those that stayed nearer to forest refuges. Chimpanzee behavioural diversity was also higher in populations of chimpanzees from savannahs compared to forest habitats and in populations experiencing greater seasonality in rainfall, suggesting that current environmental variability also shapes behavioural diversity.