Behaviour 2019
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For richer, for poorer: Mechanisms behind the benefits of mate familiarity under environmental variation
Amy Miles1, Chris Tyson1, Frédéric Angelier2, Mike Johns3, John Wingfield1, Josh Hull1. 1University of California Davis, Davis, California, United States; 2French National Centre for Biological Research, Chizé, , France; 3Point Blue Conservation Science, Petaluma, California, United States

Perennial monogamy (the maintenance of a pair bond from year to year) is one of the most extreme mating strategies animals adapt and is almost universal in seabirds. Despite its prevalence in this diverse group of birds, we know relatively little about the adaptive significance of this strategy. Emerging evidence suggests that it is during resource-poor years that the benefits of pair experience are most pronounced, but the mechanisms producing this effect  remain unknown. We followed breeding Cassin’s auklet Ptychoramphus aleuticus pairs during 2019 and 2021, years characterized by widespread breeding failure and high breeding success respectively, to explore the ecological and physiological bases of perennial monogamy, including hormones associated with energy management and parental care. By following pairs across age and experience levels, we sought to uncover how experience allows some to reproduce successfully when most others fail, and uncover the physiological and behavioral mechanisms that make perennial monogamy an adaptive reproductive strategy in a long-lived seabird.