title: Ecological drivers of group living in two populations of the communally rearing rodent, Octodon degus.
abstract: Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food availability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences.
authors.affiliation: Centro de Estudios Avanzados en Ecología and Biodiversidad, and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Ebensperger
authors.forename: Raúl
authors.initials: R
authors.lastname: Sobrero
authors.forename: Verónica
authors.initials: V
authors.lastname: Quirici
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Castro
authors.forename: Liliana Ortiz
authors.initials: LO
authors.lastname: Tolhuysen
authors.forename: Francisco
authors.initials: F
authors.lastname: Vargas
authors.forename: Joseph Robert
authors.initials: JR
authors.lastname: Burger
authors.forename: René
authors.initials: R
authors.lastname: Quispe
authors.forename: Camila P
authors.initials: CP
authors.lastname: Villavicencio
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Vásquez
authors.forename: Loren D
authors.initials: LD
authors.lastname: Hayes