Glucocorticoid levels are linked to lifetime reproductive success and survival of adult barn owls.

Paul Béziers,Fränzi Korner‐Nievergelt,Lukas Jenni,Alexandre Roulin,Bettina Almasi

doi:10.1111/jeb.13707

Abstract

Glucocorticoid hormones, such as corticosterone, are crucial in regulating daily life metabolism and energy expenditure, as well as promoting short-term physiological and behavioural responses to unpredictable environmental challenges. Therefore, glucocorticoids are considered to mediate trade-offs between survival and reproduction. Relatively little is known about how selection has shaped glucocorticoid levels. We used 15years of capture-recapture and dead recovery data combined with 13years of corticosterone and breeding success data taken on breeding barn owls (Tyto alba) to investigate such trade-offs. We found that survival was positively correlated with stress-induced corticosterone levels in both sexes, whereas annual and lifetime reproductive success (i.e. the sum of young successfully fledged during the entire reproductive career) was positively correlated with both baseline and stress-induced corticosterone levels in females only. Our results suggest that, in the barn owl, the stress-induced corticosterone response is a good proxy for adult survival and lifetime reproductive success. However, selection pressure appears to act differently on corticosterone levels of males and females.

Highlights

Baseline and acute stress-induced glucocorticoid levels can be associated with fitness components, such as reproductive success (Bonier et al, 2009a; Riechert et al, 2014; Schmid et al, 2013) and survival in adults and fledglings (Blas et al, 2007; Cabezas et al, 2007; Rivers et al, 2012; Romero and Wikelski, 2001), it is still unclear how variation in corticosterone levels affects the survival of an individual
Survival estimates There was a clear association between baseline corticosterone levels and survival probability in male but not in female barn owls (posterior probability of baseline corticosterone levels being positively associated to survival in males (98%) and females (57%)) (Table 3, Figure 2A)
Overall, our study shows that corticosterone levels are a good predictor of adult barn owl survival and that the stress-induced corticosterone response is a better predictor compared to baseline corticosterone levels

Summary

Introduction

Glucocorticoids hormones, such as corticosterone, are crucial for the functioning of organisms as they contribute to regulate a number of important physiological processes, including food intake (Dallman et al, 1993; King, 1988), energy allocation (Landys et al, 2006; Sapolsky et al, 2000) and locomotor activity (Landys et al, 2006; Overli et al, 2002a). Our knowledge about the effect of glucocorticoids on fitness traits mostly comes from studies where glucocorticoids levels have been experimentally elevated via implants and injection of glucocorticoids or with the increase of natural stressors, such as food shortage or predators (reviewed in Bonier et al, 2009a; Breuner et al, 2008; Crossin et al, 2016; Sopinka et al, 2015). In these studies, the experimental manipulation may not mimic perfectly natural situations. It is important to investigate survival in relation to natural variation in glucocorticoid levels (e.g. Blas et al, 2007; Cabezas et al, 2007; Romero and Wikelski, 2001; Wey et al, 2015; Wilkening and Ray, 2016)

Methods

Results

Discussion

Conclusion