Territory acquisition and mate choice in a monogamous mammal, the Eurasian beaver

Abstract

Territory acquisition and pair compatibility are determining factors for the fitness of territorial animals. Although these aspects are often studied separately, for territorial monogamous species acquiring a territory and obtaining a mate are not mutually exclusive. In this study, we investigated territory acquisition and mate choice characteristics in a saturated population of the Eurasian beaver, Castor fiber , by comparing individuals that successfully acquired territories with ones that were available in the study area (potential competitors). We used body mass and familiarity with an area as proxies for competitive ability, and genetic measures of inbreeding and relatedness, as well as age difference between pair members as proxies for mate compatibility. Comparatively older individuals and ones familiar with an area had a higher probability of territory acquisition, indicating that competitive ability was important for territory acquisition, whereas mate compatibility characteristics generally were not. However, in pairs that had a large age difference (between pair members), annual reproductive success decreased in more inbred pairs. These findings indicate that there might be a trade-off between territory acquisition and pair compatibility in saturated populations, that is, individuals accept being paired with a suboptimal mate when acquiring a territory, owing to intense competition. Our study emphasizes the importance of incorporating both factors related to competitive ability and mate compatibility when investigating territory acquisition in animals. • Territory acquisition and mate choice are often linked in monogamous species. • Competitive ability affects territory acquisition in beavers. • Individuals accept being paired with a suboptimal mate when acquiring a territory. • There might be a trade-off between territory acquisition and pair compatibility.