Dominance and aggression in captive gidgee skinks (Egernia stokesii)

Dominance is a key component of behaviour in many animal species and is central to social system dynamics, resource acquisition, individual fitness and ultimately reproductive success. We investigated dominance interactions and social behaviours in a group of captive juvenile gidgee skinks (Egernia stokesii). We hypothesised that a dominance hierarchy existed within the group, and that aggressive behaviours would be used to secure limited resources, especially high-value resources. We also hypothesised that body weight would be positively correlated with dominance and aggressive behaviours. We filmed the lizards at 1200 hours for six days a week over the course of eight weeks. We exposed the lizards to three different diets, which consisted of an animal-based diet (crickets), plant-based diet (plants), and a non-feeding control (no food offered). The relative value of these resources to the skinks was established through preference tests. We identified a dominance hierarchy, with dominant individuals exhibiting more aggressive behaviours than subordinates. We found that the frequency of aggressive behaviours was significantly higher in trials where high-valued resources (crickets) were at stake. Furthermore, we found a significant positive correlation between body weight and dominance, bite and chase; larger individuals were ranked higher in the social hierarchy compared to smaller individuals. Our results demonstrate the importance of morphological and behavioural traits in determining a dominance hierarchy in E. stokesii and how dominance can have ecological advantages.

Larger lizards live longer in the group-living Egernia stokesii

Animal space use has implications for gene flow, disease dynamics, mating systems and the evolution of sociality. Given recent attention to sociality in reptiles, lizards are an important group for expanding our understanding of animal space use. Lizard space use is commonly investigated within one population over a short period and limited attention has been given to potential predictors of site fidelity. This study evaluated site fidelity in three populations of group-living Egernia stokesii (gidgee skink) between two field surveys separated by almost a decade. Of 43 recaptured lizards, 28 (65%) occupied their original space, and 15 (36%) of those shared their space with the same other lizard or lizards in both surveys. This confirmed long-term site and social bond fidelity in E. stokesii. We found that larger lizards were more likely to be recaptured. Neither body size, individual genetic heterozygosity, nor the availability of refuges strongly predicted whether lizards were recaptured in the same or a different place. The reasons why some lizards stayed in the same space while others moved are yet to be resolved.

Random non-coding fragments of lizard DNA: anonymous nuclear loci for the Australian skink, Tiliqua rugosa, and their utility in other Egernia-group species

We report the development of 48 anonymous nuclear loci from the Australian skink Tiliqua rugosa using 454 sequencing. These loci amplified across a Western Australian lineage (47 loci), a ‘northern’ lineage (48 loci) and a ‘southern’ lineage (46 loci). We further tested amplification for the related T. adelaidensis and Egernia stokesii where 37 and 34 loci amplified respectively. The loci showed variability within T. rugosa (22 polymorphic loci) and at least 27 loci also exhibited variation among the three species, highlighting the usefulness of these markers for phylogenetic, phylogeographic and population genetic analyses in T. rugosa and related species.