Are extra-pair young better than within-pair young? A comparison of survival and dominance in alpine marmot [Les jeunes extra-couple sont-ils meilleurs que les jeunes intra-couple? Comparaison de survie et de domination dans la marmotte alpine].

Résumé

1. socially monogamous species, females may seek extra-pair copulation to gainbenefits. In order to test this ‘genetic quality’ hypothesis, one must compareperformance of extra-pair young (EPY) and within-pair young (WPY). Such tests,er, are scarce and results published so far are inconclusive.., we test the ‘genetic quality’ hypothesis using multistate capture–recapture models to compare age-specific survival and access to dominance between EPY and in the alpine marmot Marmota marmota, a socially monogamous mammalextra-pair paternities..compared with WPY, survival of EPY was higher by 15%, 10% and 30%, for, yearlings and 2-year-old individuals, respectively. Survival at older ages diddiffer..corresponded to true survival for yearlings and juveniles as dispersal doesoccur before 2 years of age in marmots. For older individuals, survival estimatesa mixture of survival and dispersal. The 30% increase of the 2-year-old EPYmight reflect delayed dispersal rather than high survival of EPY as comparedWPY..and EPY had the same probability (0·28) to access dominance at 2 years of age,EPY were more successful at older ages than WPY (0·46 vs. 0·10)..survival and reproductive performance were higher in EPY than in WPY. The fitness advantages of adopting such a mixed mating tactic are thus likely to be high for females. We suggest that obtaining genetic benefits is the main evolutionarydriving extra-pair paternity in alpine marmots.