Reproductive success in relation to dominance rank in the absence of prime‐age males in Barbary macaques

Abstract

In some primate species dominance rank of males is correlated with reproductive success, whereas in other species this relationship is inconsistent. Barbary macaques (Macaca sylvanus) live in a promiscuous mating system in which males are ranked in a dominance hierarchy that influences their access to females. High-ranking males usually monopolize fertile females during their estrous period and show increased mating activities. Subadult males generally rank below adult males. For Barbary macaque females in the Gibraltar colony, there was no correlation between dominance status and reproductive success. Paternity data for 31 offspring collected over four consecutive breeding seasons were used to test whether male social rank was associated with reproductive success and whether reproductive success was mainly confined to a small number of males. Genetic variation was assessed using 14 microsatellite markers for a dataset of 127 individuals sampled in all five social groups of the Gibraltar colony. Paternity analysis was conducted for offspring in one social group only, where all in-group males were sampled. Eighty-three percent of the offspring could be assigned to an in-group candidate father; none of the extra-group males appeared to have sired an infant. Male dominance rank was not found to contribute to the observed variation in male reproductive output. Fifty-nine percent of the offspring was sired by two low-ranking males, whereas the two top-ranking males sired one-fifth. A highly significant correlation was found for male age and dominance rank. Reproductive success of subadult males might be explained by the gap in the age distribution of male group members. These missing prime males are usually regarded as serious competitors for older males. Subadult males may have gained easier access to females in their absence. In addition, the presence of inbreeding avoidance mechanisms, which might also have overpowered possible rank effects, cannot be excluded.

Patterns of infant handling and relatedness in Barbary macaques (Macaca sylvanus) on Gibraltar

“…We further tested whether males that preferentially handled an infant of a given female in 1999 fathered the female's subsequent offspring in 2000. This was indeed the case for four out of five (0.80) infants born to mothers that had infants with male main handlers in 1999 (a total of nine infants were born in 2000, see Modolo and Martin 2008). This proportion is higher than the expected probability (0.37) of a male preferentially handling a female's infant and siring the female's next offspring by chance.…”

“…Paternity data were available for six out of the eight focal infants (Modolo and Martin 2008). Two out of the six infants (0.33) were sired by one of their main infant handlers.…”

“…Because of potential risks and other considerations, we were unable to trap the eight focal infants. However, we were able to use the paternity analyses conducted by Modolo and Martin (2008), which was based on samples collected following this study. This allowed us to test whether males preferentially interacted with their offspring or whether males that preferentially handled an infant of a given female had a higher probability of siring the female's subsequent offspring.…”

“…In addition, we used the paternity analysis conducted by Modolo and Martin (2008) to test whether males preferentially interacted with their offspring or whether males that preferentially handled an infant of a given female had a higher probability of siring the female's subsequent offspring.…”

When dispersal fails: unexpected genetic separation in Gibraltar macaques (Macaca sylvanus)

“…1994), the effect of dominance rank on paternity should always remain positive (van Noordwijk & van Schaik 2004). Yet, 59% of the offspring in Gibraltar were sired by two low‐ranking males, whereas the two top‐ranking males sired only one‐fifth (Modolo & Martin 2007). This unusual finding might have arisen because females may have attempted to avoid mating with familiar males, as the successful low‐ranking males were likely to be immigrants and hence ‘new’ to the females as partners.…”