Context-Dependent Fitness Outcomes of Helping in the Cooperatively-Breeding Florida Scrub-Jay (Aphelocoma coerulescens)

Cooperatively breeding species frequently live in family groups of related individuals, with helpers delaying their own reproduction and participating in alloparental care, predator vigilance, and territory defense. It remains challenging to disentangle the roles of the indirect fitness benefits of helping kin and the potential direct fitness benefits helpers receive in the evolution of cooperative breeding. While many studies test for associations between helper relatedness and helping effort, few estimate the realized fitness consequences of helping in relation to these factors. Understanding these fitness outcomes elucidates the selective forces that maintain helping behavior, whether through inclusive fitness gains by helping related individuals or as a means of gaining access to later direct fitness benefits. Using 29 years of extensive demographic data from a closely monitored population of Florida scrub-jays (Aphelocoma coerulescens), we quantified the effect of helpers on breeder survival, offspring survival, and nestling production and how these effects depend on relatedness and sex of helpers. We found that female breeder survival was significantly greater when more helpers were present and that offspring survival was greater when more male helpers were present on small territories. Neither effect of helpers depended on the relatedness between helpers and the individuals they helped. Our results suggest that helping behavior is highly context-dependent and varies based on the potential impact of helping and the direct fitness benefits helpers receive.