Social environment interacts with functional microsatellite polymorphism of Avpr-1a to drive extra-pair paternity occurrence in the Alpine marmot (Marmota marmota). Extrinsic and intrinsic constraints interact to drive extra-pair paternities in the Alpine marmot

To reproduce, animals have to form pairs but large variations in the degree of mate retention are observed. Extrinsic and intrinsic factors can constrain individual’s mate switching. Among intrinsic factors, genes involved in pair-bonding, such as Avpr-1a, receive increasing attention. The length of microsatellites present in the regulatory region of Avpr-1a determines the densities and distributions of the vasopressin receptors known to impact monogamous behaviours. For the first time, we investigated if and how the genetic makeup at Avpr-1a and the social context experienced by wild Alpine marmot females affect their extra-pair matings. The proportion of extra-pair young depended on the length of their Avpr-1a regulatory region but only when the social constraints were relaxed, i.e. when mature male subordinates were present. Under natural conditions, the genetic regulation of pair-bonding could thus be hidden by extrinsic factors constraining mate choice.