Effect of group size and composition on individual behavior, group dynamics and population regulation in the Arabian babbler (Turdoides squamiceps)

Cooperative breeding is a social system in which individuals help care for young that are not their own. Considerable research has found that cooperation can result in a number of benefits for group members, including enhanced reproductive success and greater longevity. These benefits lead to the possibility that the social structure of the group an individual comes from may have important long-term fitness consequences. However, little is known about the relative importance of social and environmental factors on individual fitness traits and group dynamics in the long-term in cooperatively breeding species. Thus, long-term studies on how social and environmental factors influence the costs and benefits of cooperative behaviour are of extreme importance. In this thesis I explore how social and environmental factors influences the individual, the group and the population in cooperatively breeding Arabian babblers (Turdoides squamiceps). I did that by (a) experimentally investigating the factors influencing individual foraging strategies and innovative behaviour, (b) analysing a long-term database to study the effect of social and environmental factors on individual fitness traits and group dynamics, and (c) determining whether inverse density dependence (Allee effects) occurs at both the group and population level. I found that dominant and subordinate individuals differ in both foraging and cognitive strategies, and that novel foraging skills may be socially transmitted, outlining an important benefit of group-living. I also found that group size and reproductive competition significantly affected reproductive success and group dynamics, suggesting that social factors are important influences on both individual fitness and group demography. Finally, I found the existence of both group and demographic Allee effects in the study population, which represents an important consideration for the management and protection of cooperatively breeding species. These findings provides novel approaches that may benefit further studies on individual fitness and group dynamics in cooperative breeders.