Habitat complexity modulates social structure: experimental evidence from replicated social networks of wild sleepy lizards (#179)
The social structure is a fundamental part of a population driving many ecological and evolutionary processes ranging from parasite transmission to sexual selection. Despite being a long standing interest of animal ecology, we still don’t understand many sources of variation in social structure among populations of the same species. We capitalised on recent advances in bio-logging and social network techniques to experimentally evaluate how environmental conditions, in this case habitat complexity, modulate social structure at different levels in wild populations. The Australian sleepy lizard (Tiliqua rugosa) establishes non-random social networks that are characterised by avoidance of some individuals, and frequent interactions with an opposite sex individual reflecting the pair-living social organisation. We experimentally increased habitat complexity in two populations by adding maze-like structures and compared the social dynamics of those populations to two control populations. We used data from GPS-tracking all adult individuals every ten minutes in these populations to construct social networks based on spatial proximity of individuals. Social connectivity (network density) and social stability across weekly intervals were greater in populations with higher habitat complexity than in control populations. Social differentiation (coefficient of variation of dyadic association frequencies) reflecting the pair-living social organisation remained similar. Greater social connectivity resulted in higher rates of agonistic interactions, shown by higher individual scale damage in those populations. Furthermore, males and females that interacted most often with a same sex individual had greater scale damage, suggesting that intra-sexual competition among both sexes shaped the social structure.