In this study we used data from six unlinked microsatellite loci to examine stable aggregations of Egernia stokesii, from a population in the southern Flinders Ranges of South Australia. We show that these aggregations are comprised of breeding partners, their offspring from two or more cohorts, and related adults, providing the first genetic evidence of a family structure in any lizard species. Despite this high level of relatedness within aggregations, most breeding pairs were unrelated and partners were less closely related to each other than they were to other potential within-group partners. Where individuals dispersed, both sexes usually moved to social groups close to their natal group. Although both sexes showed natal philopatry, there was some evidence that females in groups were more related than males in groups. These data suggest that an active choice of unrelated partners and male-biased dispersal may be the mechanisms used by E. stokesii to avoid inbreeding within groups.

Social groups in many animal species contain family members, and are maintained by parental care, and then tolerance of related individuals in the group. Lizards rarely show prolonged parental care, and rarely form stable social aggregations, although cohesive groups have been reported in the Australian skink genus, Egernia. A population of Egernia stokesii was surveyed for six seasons on Camel Hill, South Australia. At this site individuals occupied rock crevices for refuges on an isolated rocky outcrop of about 1.5 ha. The population was divided into 17 stable social groups, each containing 2-17 individual lizards. Surveyed juveniles took more than 5 years to reach mature size, and most juveniles and subadults remained in the social group of their parents for that period and longer. There were 2-8 permanent adult members of each group. Group members shared common crevice refuges, basked close together (and sometimes on top of each other) and defecated in common scat piles. There was low mortality after the first 2 years of life, and low dispersal either into or out of the population. Some individuals were "floaters" that did not belong to a social group. Over the study a number of these became established in groups. The social structure of these lizards resembles the family groups reported in many species of birds and mammals where group members help to raise the offspring of relatives. The low level of parental care in lizards suggests that the evolution of this form of social organisation in lizards has resulted from different processes than in other vertebrate taxa.

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A newly described tick species, Amblyomma vikirri, infests two lizard species in the Flinders Ranges of South Australia. Although one of the hosts, Tiliqua rugosa, has a wide distribution, the tick distribution is restricted to a subset of rocky habitats where the other host, Egernia stokesii, lives. Experiments were conducted with unfed ticks, the stage when the tick is waiting for a host and is susceptible to desiccation. Amblyomma vikirri had a significantly stronger preference for rock microhabitats than two other tick species {Aponomma hydrosauri and Amblyomma limbatum) that infest T. rugosa. Unfed Amb. vikirri were also more active than the other two species, and more likely to be in the upper part of the substrate. At warm temperatures, larvae oi Amb. vikirri survived for shorter periods under desiccation stress than larvae of the other two species, although as nymphs Amb. vikirri survived as well or better. The rock crevice microhabitat experienced lower maximum temperatures than other potential, non-rock refuge sites. The behaviour of Amb. vikirri, its susceptibility to desiccation in the larval stage and the relatively benign conditions in the rock crevices may act together to prevent Amb. vikirri establishing populations beyond rock habitat.