Forest elephants: fission-fusion and social arenas

Abstract

Fission-fusion systems provide models for studying grouping decisions and social complexity in a range of taxa, as individuals act to manage risks and enhance reproductive success. African savannah elephants, Loxodonta africana africana, live in a fluid society where individual relationships persist over decades and affect reproductive success. Social structures have yet to be fully characterized for forest elephants, Loxodonta africana cyclotis. Aggregations at natural forest clearings, which are frequent in this subspecies, may offer social benefits in addition to nutritional resources. We examined the social functions of aggregations in Odzala-Kokoua National Park, Republic of Congo. We tested whether clearings function as ‘social arenas' by examining how social opportunities affected the timing and duration of visits, and how short-term grouping decisions were affected by age, sex, group size and number of elephants present. Aggregations reflected a fission-fusion society similar to that observed in savannah elephants. Grouping patterns were largely unaffected by the number of elephants present, from which we infer that elephants were not acting to minimize competition. Social opportunities affected visit patterns such that visits were longer when others were present. Social opportunities were maximized by joining large groups, often including older elephants, or, for males, parties with females. Large and dynamically changing social groups in clearings offer potential for information exchange and the maintenance of social relationships. Demonstrating that fission-fusion operates in forest elephant society allows future research to focus on cost-benefit modelling, to understand the fitness consequences of these groupings.