Ecological drivers of group living in two populations of the communally rearing rodent, Octodon degus

摘要

Intraspecific variation in sociality is thought toreflect a trade-off between current fitness benefits and coststhat emerge from individuals' decision to join or leavegroups. Since those benefits and costs may be influencedby ecological conditions, ecological variation remains amajor, ultimate cause of intraspecific variation in sociality.Intraspecific comparisons of mammalian sociality acrosspopulations facing different environmental conditions havenot provided a consistent relationship between ecologicalvariation and group-living. Thus, we studied two populationsof the communally rearing rodent Octodon degus todetermine how co-variation between sociality and ecologysupports alternative ecological causes of group living. Inparticular, we examined how variables linked to predationrisk, thermal conditions, burrowing costs, and food availabilitypredicted temporal and population variation insociality. Our study revealed population and temporalvariation in total group size and group composition thatcovaried with population and yearly differences in ecology.In particular, predation risk and burrowing costs aresupported as drivers of this social variation in degus.Thermal differences, food quantity and quality were notsignificant predictors of social group size. In contrast tobetween populations, social variation within populationswas largely uncoupled from ecological differences.