The response of a sleepy lizard social network to altered ecological conditions

The use of social networks to describe animal social structure is increasing, yet our understanding of how social networks respond to changing ecological conditions remains limited. Animal behaviour is often constrained by temporal or spatial variation in ecological conditions; how do behaviour and social organization respond to changing ecological conditions? We used a social network approach to ask this question in the pair-living sleepy lizard, Tiliqua rugosa. We attached GPS data loggers to lizards to record their movement, activity and social interactions during their activity period (October-December) in 2008-2010. The years varied substantially in ecological conditions, from hot and dry in 2008 to cool and wet in 2010. Our aim was not to suggest how individual climatic or ecological factors influence social organization, but to explore the stability of social structure over varying conditions. Lizards spent less time active and overlapped in home range area more with conspecifics in the driest year of the study (2008) than in subsequent years. Despite this variation in behaviour, the number and strength of connections in the social network were stable across years. Intrasexual associations were similar across years, but there was a lower incidence of intersexual associations in 2008 than in the other 2 years. Among male-female dyads, pairing intensity was lower in 2008, while for males, extrapair strength was higher in 2008. These results suggest that although the overall social network is tolerant to changes in ecological conditions, the nature of contacts within the network shifts in response to ecological variation.