Stress levels of dominants reflect underlying conflicts with subordinates in a cooperatively breeding species

Assessing stress physiology within a conservation breeding program for an endangered species

Conservation breeding programs typically involve the management of individuals both in and ex situ, so it is vital to understand how the physiology of managed species changes in these environments to maximize program outcomes. The Vancouver Island marmot (VIM; Marmota vancouverensis) is one species that has been managed in a conservation breeding program to recover the critically low wild population. Previous research has shown there are differences in hair glucocorticoid concentrations for VIMs in different managed groups in the program. Therefore, we used >1000 blood samples collected since the program's inception to assess the neutrophil to lymphocyte (N:L) ratio among captive, pre-release, post-release and wild populations as another metric of stress. In situ VIM populations were found to have a significantly higher N:L ratio than ex situ populations, suggesting that the wild is a more physiologically challenging environment than managed care. Moreover, the effect of age, sex and the month of sampling on the N:L ratio were found to be different for each population. Age had the greatest magnitude of effect in the wild population, and sex was only significant in ex situ populations. This study provided previously unknown insights into the physiology of VIMs and increased post-release monitoring will be useful in the future to fully understand how physiology may be contributing to differences in survival of VIMs in the program.

Is degree of sociality associated with reproductive senescence? A comparative analysis across birds and mammals

Our understanding on how widespread reproductive senescence is in the wild and how the onset and rate of reproductive senescence vary among species in relation to life histories and lifestyles is currently limited. More specifically, whether the species-specific degree of sociality is linked to the occurrence, onset and rate of reproductive senescence remains unknown. Here, we investigate these questions using phylogenetic comparative analyses across 36 bird and 101 mammal species encompassing a wide array of life histories, lifestyles and social traits. We found that female reproductive senescence: (i) is widespread and occurs with similar frequency (about two-thirds) in birds and mammals; (ii) occurs later in life and is slower in birds than in similar-sized mammals; (iii) occurs later in life and is slower with an increasingly slower pace of life in both vertebrate classes; and (iv) is only weakly associated, if any, with the degree of sociality in both classes after accounting for the effect of body size and pace of life. However, when removing the effect of species differences in pace of life, a higher degree of sociality was associated with later and weaker reproductive senescence in females, which suggests that the degree of sociality is either indirectly related to reproductive senescence via the pace of life or simply a direct outcome of the pace of life. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'