Familiarity breeds progeny: sociality increases reproductive success in adult male ring‐tailed coatis ( Nasua nasua )

The ring‐tailed coati ( Nasua nasua ) is the only coati species in which social groups contain an adult male year round, although most males live solitarily. We compared reproductive success of group living and solitary adult male coatis to determine the degree to which sociality affects reproductive success. Coati mating is highly seasonal and groups of female coatis come into oestrus during the same 1–2 week period. During the mating season, solitary adult males followed groups and fought with the group living male. This aggression was presumably to gain access to receptive females. We expected that high reproductive synchrony would make it difficult or impossible for the one group living male to monopolize and defend the group of oestrous females. However, we found that group living males sired between 67–91% of the offspring in their groups. This reproductive monopolization is much higher than other species of mammals with comparably short mating seasons. Clearly, living in a group greatly enhanced a male’s reproductive success. At the same time, at least 50% of coati litters contained offspring sired by extra‐group males (usually only one offspring per litter); thus, resident males could not prevent extra‐group matings. The resident male’s reproductive advantage may reflect female preference for a resident male strong enough to fend off competing males.