Extended safe havens and between-group dispersal of helpers in a cooperatively breeding cichlid

Abstract In cooperative breeders, between-group dispersal of helpers is expected to occur if it increases their fitness. Genetic data suggest that helpers in the cooperatively breeding Lake Tanganyika cichlid Neolamprologus pulcher occasionally migrate into nearby groups where they again become helpers. We studied in the field how and why helpers migrate between groups by recording their ranging and social behaviours. We found that helpers spent 5.3% of their time visiting other groups, where they received similar low levels of aggression as within their home group. Large helpers visited other groups more often than small helpers and helpers visited other groups more frequently when the queue in their home group was large, suggesting that helpers with low chances to inherit the territory search for alternatives. Our data show that helpers may use other groups' territories as a refuge, as helpers actively sought shelter within territories of neighbouring groups when we experimentally increased the perceived risk of staying in their home territory. We observed two attempted and one successful case of 'voluntary' (i.e., strategic) between-group dispersal, and experimentally induced three helpers to disperse into other groups. By regular visits, helpers appear to establish familiarity and social relationships with nearby groups, which serve as 'extended safe havens' to hide from predators. In the long run frequent visiting behaviour may facilitate between group dispersal.