Extreme and variable environmental temperatures are linked to reduction of social network cohesiveness in a highly social passerine

摘要

Organisms living in hot, arid environments face important risks associated with hyperthermia and dehydration which are expected to become more severe with climate change. To mitigate these risks, individuals often modify behaviour, e.g. reducing activity and seeking shade. These behavioural modifications may affect interactions between individuals, with consequences for the social structure of groups. We tested whether the social structure of cooperative groups of sociable weavers Philetairus socius varied with environmental temperature. We recorded the nature and frequency of interactions at feeders positioned beneath three sociable weaver colonies (n =49 identified birds) in the Kalahari Desert with respect to environmental temperatures over a 30-day period. Using random forest models, we examined whether thermal conditions predicted variation in social network structure. We also conducted focal observations of individual weavers to assess functional links between temperature, intensity of heat dissipation behaviour (panting) and immediate effects on social behaviour. Our results suggest that the social structure of weaver colonies becomes less cohesive and more fragmented at extreme and variable environmental temperatures. These changes in network structure appear to be linked with individuals' heat dissipation behaviour: extreme and variable temperatures were associated with increased panting, which was significantly correlated with an immediate reduction in the frequency of association. Collectively, our results indicate that interactions within groups could be disturbed by environmental temperature variation and extremes. Changing temperature regimes could therefore affect the functioning of animal societies by altering social networks.