Group Structure and Stability in Social Aggregations of White's Skink, Egernia whitii

Abstract

Most lizards display relatively simple social systems, but more complexand stable social aggregations appear to be common in one lineage ofAustralian skinks, the Egernia Group. Previous studies on this lineagehave focused on species inhabiting crevices in large and disjunct rockyoutcrops. Here, we describe the social organization of White’s skink,Egernia whitii, a burrowing species that inhabits rocky habitats in south-eastern Australia. We examined social group size, composition andstability over two field seasons using a capture-mark-recapture study,behavioral observations and genetic analyses. Twenty-four social groups,each comprising two to six individuals, were present at our study site,with 75% of lizards belonging to a social grouping. A higher proportionof adults than juveniles were part of a group, while more adult femalesbelonged to a group than adult males. Groups generally comprised asingle adult pair or an adult pair with juveniles. However, groups com-prising one male with multiple females and multiple individuals of bothsexes also were present. Groups were highly stable throughout thestudy, although individual group members were observed singly on halfof all observations. Paternity analysis using four microsatellite locirevealed that juveniles within groups were closely related to adults inthe group, with 38% living in groups with both parents and 71% ingroups with at least one parent. Our data demonstrate the presence ofcomplex sociality in a burrowing Egernia species and, together with pre-vious studies, suggest that stable social organization is widespread acrossdifferent habitats and phylogenetic groupings within the Egernia Group.