Paying to stay or paying to breed? Field evidence for direct benefits of helping behavior in a cooperatively breeding fish

Several hypotheses aim to explain the evolution of helping behavior, but co nclusive experimental support for evaluating the relative importance of ind ividual hypotheses is still lacking. We report on two field experiments con ducted to test the "territory inheritance" and "pay-to-stay" hypotheses in the cooperatively breeding cichlid fish Neolamprologus pulcher. The territo ry inheritance hypothesis was tested by removing one parent, which created breeding vacancies. In 39% of cases, same-sex helpers took over the breedin g spot; in 44% of cases helpers continued helping new breeders, and 17% wer e evicted by new breeders. Helpers that were closely size matched to the re moved breeder had a better chance of gaining the breeding spot. Male helper s tended to continue helping after a takeover more often than females. The pay-to-stay hypothesis was tested by temporarily removing helpers. Whereas breeders did not respond aggressively to removals, other group members atta cked the removed helpers on their return, and 29% were eventually evicted. The returning helpers assisted more by increasing their rate of territory m aintenance and defense and visiting the brood chamber more frequently Size and sex of removed helpers did not explain the observed aggressive reaction s of other group members. Thus, our results support both hypotheses: N. pul cher needs to pay with help to be allowed to remain protected in the family group, and there they may inherit the natal territory. N. pulcher helpers gain direct benefits from helping behavior.