Egernia are a group of family-living lizards that occur throughout Australasia. The group comprises approximately 60 species from seven different genera. They contain a number of iconic Australian lizards like the bluetongue lizard (Tiliqua scincoides), the sleepy lizard (Tiliqua rugosa) and the wonderfully named ‘land mullet’ (Egernia major).

egernia
Variation in group living amongst members of the Egernia group, from the pair living sleepy lizard (Tiliqua Rugosa) to the family living black rock skink (Egernia saxitilis) and the communal living gidgee skink (Egernia stokesii) (photo credits Dave Buzacott and Dave O’Connor)

One of the most striking features of Egernia is that they include highly social lizards that form stable social aggregations based around kin (e.g., the live in family groups). Specifically, while some species are largely solitary, in others males and females form long-term pair-bonds sometimes holding territories where juveniles can remain with their parents. In the most extreme cases this can lead to large communal groups of up to 30 related individuals, including non-breeding adults who stay within their parent’s social group. They also display several other unique features that we believe are related to their unusual social lifestyle. For example, unlike all other reptiles, Egernia give birth to offspring asynchronously, this is analogous to hatching asynchrony in birds and results in strong competitive asymmetries emerging within the brood. Why and how females achieve this is still largely unknown.

Our research attempts to understand the origin and evolution of this social complexity. We do this by combining long-term field studies of natural populations with experimental work, often involving semi-natural enclosures where we study how social bonds are formed, maintained, and why they sometimes are dissolved. Most of this work is done on the White’s skink (Liopholis whitii), however we have analogous systems in Egernia striolata, Egernia stokesii as well as several other species. The ultimate goal of this research is to connect our understanding of the micro-evolutionary processes operating within species to the macro-evolutionary patterns of social diversification we see across the group. This will help us to understand the early steps in vertebrate sociality, including the formation of benign parent-offspring relations after birth, something that is not very common in lizards. For more on Egernia biology, see our Quick Guide in Current Biology or listen to Geoff’s interview on ABC radio here.

 

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