Genetic evidence of promiscuity in a mammal without apparent sexual dimorphism, the white-lipped peccary (Tayassu pecari)

Polygyny in mammals, as in other groups, is related to sexual dimorphism, with males being larger than females or with elaborate weaponry as a response to sexual selection. However, sexual selection can also act on females, leading to cases where dimorphism is reversed or absent and females mate with several males, leading to a promiscuous mating system. In this study, we analyzed the mating system of a monomorphic mammalian species, the white-lipped peccary (Tayassu pecari), using microsatellite molecular markers and parentage tests. The white-lipped peccary mating system is predicted to be polygyny, but so far, no systematic study exists. To verify their mating behavior, 131 individuals of a herd from the Brazilian Pantanal were genotyped for 11 microsatellite loci and parentage tests were performed for all the sampled young. We determined that both males and females had offspring with more than one partner which is compatible with a promiscuous mating system. Promiscuity in this species could be related to competition among females as a result of the female-biased sex ratio leading to sexual and/or natural selection not only on males but also females.