Predation risk promotes delayed dispersal in the cooperatively breeding cichlid Neolamprologus obscurus

Delayed dispersal of offspring from the natal territory is an important process in the evolution of cooperative breeding. Ecological constraints such as habitat saturation can promote delayed dispersal. Thus far, the role of predation risk in the evolution of cooperative breeding systems has received less attention, although it is understood as an important ecological factor shaping dispersal patterns and social structure in animals. To bridge this gap, we analysed group structure and dispersal patterns of helpers within a population of the cooperatively breeding cichlid Neolamprologus obscurus. We conducted behavioural observations for a period of 3 months at two study sites within this population, which differed in predation risk and availability of unoccupied space. Furthermore, by combining field observations with molecular analyses, we assessed group structure to unravel the dispersal patterns of helpers. At the high predation risk location, we found that helpers (1) had a lower dispersal propensity, (2) dispersed shorter distances and (3) were generally larger. Furthermore, molecular analyses and body size measurements suggest that helpers may stay longer in the natal territory under high predation risk than under low predation risk. Groups contained more helpers in the high predation risk site, which indicates that high predation pressure leads to delayed dispersal of helpers. Unoccupied potential dispersal areas were larger in the high predation risk site, suggesting that habitat saturation did not account for the dispersal patterns. Our results suggest that predation pressure is the main factor limiting the dispersal of helpers in the cooperatively breeding cichlid fish N. obscurus, and might be overlooked in other studies focusing on the evolution of cooperative breeding systems.