Anal scent gland secretions inform on sexual maturity, sex and social status in the Alpine marmot, Marmota marmota (Rodentia: Sciuridae): a role in intrasexual competition in cooperative breeders?

Résumé

In cooperative breeders, reproductive skew is extreme and leads to intense intrasexual competition for access to reproduction in both sexes. Given that securing the dominant position is costly, dominant animals should direct their aggressiveness towards same-sex subordinates that are potential competitors. Chemical communication has been reported to be involved in intrasexual competition in several mammalian species, and odour may be used as a cue to identify potential competitors. We predicted that odour should inform on sexual maturity, sex and social status in cooperative breeders. We tested these predictions in the Alpine marmot, a cooperatively breeding species, in which anal gland secretions are involved in aggressive behaviour. We sampled anal gland scents from 154 individuals of differing sexual maturity status, sex and social status. We found that anal gland secretions may inform on sexual maturity. When focusing on adult individuals, we found that anal gland scent differed according to sex and social status. Our results support the hypothesis that anal gland scent could be involved in intrasexual competition in Alpine marmots by allowing dominant individuals to target their aggressiveness towards same-sex competitors (i.e. sexually mature subordinates), resulting in the reproductive suppression of subordinates.