Social networks in African elephants

摘要

Some of the most highly social animals-including elephants, and some primates, cetaceans, and social carnivores-live in "fission-fusion" societies where social groups divide and re-form over the course of hours, days, or weeks. These societies are thought to respond adaptively to changes in the physical and social environment, and are thus ideal for testing hypotheses about the evolutionary forces that shape sociality. However, few models have been developed to measure and explain fission-fusion dynamics. Here we isolate several key components of the social behavior of wild African elephants (Loxodonta africana) using a bilinear mixed effects model, proposed by Peter Hoff (J. Am. Stat. Assoc. 100(469):286-295, 2005). The model enables inference on environmental effects, such as rainfall and seasonality, and is flexible enough to include predictors of pairwise affiliation, such as kinship, which allows large-mammal ecologists to test assumptions about elephant social structure and to develop new theories of why and how elephants interact. In addition, this model includes an unobserved latent social space to represent the interactions between elephants not incorporated by the measured covariates.