Data from: Highly masculinized and younger males attain higher reproductive success in a social rodent

Abstract: Alternative morphotypes have been reported in males of different
taxa. In some mammals highly masculinized and slightly masculinized males
represent two opposite ends along a gradient of phenotypic variation in
males. This phenotypical gradient originates during prenatal development.
Laboratory studies have documented how highly and slightly masculinized
males differ in several traits, including their reproductive success.
However, the extent to which these reported differences materialize in
natural populations remains unknown. We quantified the impact of male
morphotype on male reproductive success in a natural population of Octodon
degus, a highly social rodent. We assessed male morphotype through a
continuous gradient of anogenital distance. We also tested the hypothesis
that the social environment interacts with male morphotype to influence
male reproductive success. We found that individual attributes, including
masculinization level and age, impacted male reproductive success. Highly
masculinized and younger males had greater reproductive success.
Additionally, male body weight had a small magnitude but positive effect
on male reproductive success. Male reproductive success was not affected
by social attributes such as group composition. Thus, the number of males
and females within a group did not affect male reproductive success, nor
did the average male anogenital distance within a group. Our results
support the hypothesis that the prenatal environment can result in
long-term effects on individual life history and cause intrasexual
phenotypical variation in natural populations. Our findings suggest that
male phenotypical masculinization could be an adaptive trait, regardless
of the social environment.