Seeking smarts: Male chickadees with better spatial cognition sire more extra-pair young

Across the animal kingdom, females commonly mate with more than one male even when they are monogamous. Extra-pair males rarely contribute resources outside of sperm, therefore, many hypotheses surrounding the fitness benefits of extra-pair (EP) paternity involve genetic mechanisms. The ‘good genes’ hypothesis suggests that socially monogamous females mate outside their pair bond to increase the fitness of their offspring via indirect genetic benefits. We tested this hypothesis by quantifying extra-pair paternity in nonmigratory, food-caching mountain chickadees ( Poecile gambeli ). Chickadees rely on spatial cognition to recover scattered food caches and variation in spatial cognition is associated with increased survival, longer lifespan, and is heritable, however, less is known about the relationship between reproductive success and spatial cognition. In the current study, we had two main objectives; to assess the relationship between spatial cognition and reproductive output via extra-pair young and to compare the spatial cognition of EP males to the within pair males they cuckolded. We found that 1. males with better spatial cognitive abilities have more extra-pair young and produce heavier offspring in their own nests compared to their poorer performing counterparts, and 2. EP males have significantly better spatial cognition than the social males they cuckolded. These results show that males with better spatial cognitive abilities exhibit higher reproductive success and are consistent with the good genes hypothesis if females gain genetic benefits associated with better cognitive abilities via EP young.