Data from: Masculinized females produce heavier offspring in a group living rodent

Alternative morphotypes have been reported less frequently in females than
in males. An exception to this rule is the gradient of phenotypical
masculinization reported in some female mammals, in which feminized and
masculinized females represent two opposite ends along this gradient.
These phenotypical differences originate during prenatal development as
the consequence of maternal effects. Feminized and masculinized females
differ in several traits, including morphological, physiological,
behavioural and reproductive traits. Differences previously reported in
reproductive traits between feminized and masculinized females come mostly
from mechanistic studies performed in the laboratory, and not necessarily
on social species. As a result, it is unclear to what extent these
reported differences between female alternative morphotypes materialize in
wild, natural populations. We quantified the effect of female alternative
morphotype on female reproductive traits in a natural population of
Octodon degus, a highly social rodent. We assessed female alternative
morphotype through a continuous gradient of anogenital distance. Thus,
feminized females were close to the short end of anogenital distance,
while masculinized females were close to the long end of this gradient. We
also tested the hypothesis that the social environment interacts with
female morphotype to influence female reproductive traits. In female
degus, only body weight affected litter size, where heavier females weaned
more offspring. Masculinized females delivered male-biased litters and
weaned heavier offspring. Lastly, masculinized females gave birth later in
the breeding season compared to feminized females. Contrary to previous
claims, our findings do not support that masculinized females are less
fertile than feminized females. Moreover, masculinized females produced
heavier, potentially higher quality offspring compared with feminized
females.