Data from: Relatedness and age reduce aggressive male interactions over mating in domestic fowl

Altruistic behaviour represents a fundamental challenge in evolutionary
biology. It is often best understood through kin selection, where
favourable behaviour is directed towards relatives. Kin selection can take
place when males cooperate to enhance the reproductive success of
relatives. Here, we focus on reduced male–male competition over mating as
a case of cooperation, by examining male tolerance of matings by related
and unrelated competitors. A suitable model for exploring whether
relatedness affects male–male interactions over mating is the domestic
fowl, Gallus gallus domesticus. In this species, males form social
hierarchies and dominant males commonly interrupt subdominant males’
copulation attempts. We investigated whether dominant male fowl
differentially direct aggressive interactions towards unrelated and
related subordinate males during mating attempts. Dominant male fowl were
found to interrupt mating attempts of male relatives less often than those
of unrelated males. We further tested whether male age mediates the
magnitude of kin tolerance behaviour. However, we found no support for
this as both young and old dominant males were less likely to interrupt
related, compared to unrelated, subdominant males’ copulations during
male–male interactions. Our results, consistent with kin selection,
provide a rare experimental demonstration of relatedness relaxing
male–male competition over mating.