Sociable weavers are highly cooperative birds that work together to accomplish diverse tasks, from building their highly distinctive communal nests to help raising the chicks of others or defending the colony from predators. Their multi-level society and different types of cooperative behaviours make them an ideal study model to investigate the benefits and costs of sociality and the evolutionary mechanisms that allow cooperation to evolve and be maintained.
Currently, much of our research addresses the following themes:
1. The role of partner choice in the evolution and of cooperation.
Theoretical models show that if more cooperative individuals are preferred as sexual or social partners, cooperation is more advantageous than cheating or defecting, and studies in humans have shown a preference for associating with more cooperative individuals. However, field tests of these mechanisms have been difficult to conduct and the results are mixed. We are using micro-tracking, social networks analyses and long-term data to examine social and sexual partner choice in this species and its potential role for the evolution of cooperation. This project is funded by the European Research Council (ERC, Consolidator grant 8866489 to R. Covas) and the French National Research Agency (ANR, AAPG2019 to C. Doutrelant).
2.Does sociality mitigate the role of adverse conditions?
Sociality and, in particular, cooperative breeding are thought to buffer against the effects of adverse climatic conditions. This could be particularly important given that the frequency and intensity of extreme weather events such as droughts and heat waves, is predicted to increase under the current climate change scenario. We use our long-term data to establish whether sociality may lessen the impacts of these adverse conditions at the individual and population level.
3. Effects of natural catastrophes
The frequency of extreme weather events has been increasing markedly under anthropogenic climate change, and these events can lead to natural catastrophes such as floods or destructive fires. The consequences of these events for organisms are not yet well understood, partly because they are relatively rare and unpredictable in occurrence. A large-scale fire in September 2021 destroyed two thirds of our study colonies at Benfontein. This forced the surviving birds to immigrate into the remaining colonies, leading to a marked increase in size of the surviving colonies (some trebled in size) and also in the level of aggressive interactions. Our continuous monitoring of this population provides a unique opportunity to study the consequences of events of this magnitude on the surviving individuals. We are currently studying how the fire influenced social structure, physiology and survival rates. We are also interested in understanding whether social factors promote resilience to extreme events such as this.
4. Conflict and infanticide
In all cooperative societies there is also conflict and even extreme asocial behaviours, such as infanticide. We collect long-term data with the aim of understanding which factors ultimately influence the balance between cooperation and conflict in our system
