How social behaviour and life-history traits change with age and in the year prior to death in female yellow-bellied marmots.

Studies in natural populations are essential to understand the evolutionary ecology of senescence and terminal allocation. While there are an increasing number of studies investigating late-life variation in different life-history traits of wild populations, little is known about these patterns in social behaviour. We used long-term individual based data on yellow-bellied marmots (Marmota flaviventer) to quantify how affiliative social behaviours and different life-history traits vary with age and in the last year of life, and how patterns compare between the two. We found that some social behaviours and all life-history traits varied with age, whereas terminal last year of life effects were only observed in life-history traits. Our results imply that affiliative social behaviours do not act as a mechanism to adjust allocation among traits when close to death, and highlight the importance of adopting an integrative approach, studying late-life variation and senescence across multiple different traits, to allow the identification of potential trade-offs. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'