Breeding and predation risk mediate central place foraging in a cooperative breeder, jungle babbler

Abstract

Space use in animals is shaped by various socio-ecological factors such as reproductive status, resource availability, predation risk and additionally by group size in the case of social animals. These, in turn, influence the foraging decisions of animals. We examined these drivers in a cooperatively breeding bird, the jungle babbler (Argya striata), using field-based observations and manipulative experiments. We found that territory size in jungle babblers reduced by ∼78% during breeding. This reduction was not explained by resource availability, instead it reflects reproductive constraints, with groups adopting a central place foraging strategy around nest. During breeding, groups exhibited lower mean square displacement, spent more time near the nest, exhibited higher patch residence time and lower patch revisitation, indicative of restricted movement and foraging constraints on groups. These results are also in line with the ‘prudent parent’ framework. Group size effects on foraging were context dependent, wherein larger groups tended to show increased patch residence time during breeding contrary to the predictions of optimal foraging models for social animals. Results of predator-simulated experiments, demonstrate that nest defence significantly impacted movement patterns and that anti-predator response was influenced by group size. Overall, our study highlights the complex role of reproductive status, group size, resource availability and predation risk in determining space use patterns and foraging decision-making in social animals. It also tests the predictions of the social patch model and identifies avenues for further improvements in the model.