Physiological stress levels predict survival probabilities in wild rabbits

Abstract

Among vertebrates, short-term elevations of glucocorticoid hormones (corticosterone or cortisol) facilitate a suite of physiological and behavioral changes aimed at overcoming environmental perturbations or other stressful events. However, chronically elevated glucocorticoids can have deleterious physiological consequences, and it is still unclear as to what constitutes an adaptive physiological response to long-term stress. In this study, we experimentally exposed European wild rabbits Oryctolagus cuniculus to a source of long-term stress (simulated through a 2- to 4-week period of captivity) and tested whether glucocorticoid physiology predicted two major components of rabbit fitness: body condition and survival probability. Following exposure to long-term stress, moderately elevated serum corticosterone and fecal glucocorticoid metabolites levels in the wild rabbits were negatively associated with body condition, but positively associated with subsequent survival upon release. Our results suggest that the cost of maintaining elevated corticosterone levels in terms of decreased body condition is balanced by the increased chance of survival upon release.

Stress response during development predicts fitness in a wild, long lived vertebrate

“…Recent studies in wild populations of mammals, birds, and reptiles have reported associations between baseline (18) or chronic (6, 7) GC levels and survival. However, this association is ultimately confounded by differential exposure to stressors among individuals, affecting circulating GC levels, or relates to short-term survival (7). In contrast, our results relate long-term survival and recruitment to the nature of an individual's physiological response to a standardized source of stress.…”

Hormonally mediated maternal effects, individual strategy and global change

“…the corticosteronefitness hypothesis [145], through infertility, impaired resistance to disease and inhibition of growth [49,84]. In contrast, other studies suggest that elevated corticosterone promotes adaptive advantages to the individual forming the corticosterone-adaptation hypothesis, [131,146]. Experimental manipulations of corticosterone reveal the complexity of the relationship between corticosterone and fitness.…”

“…In some years, exogenous corticosterone implants may have a positive effect on total clutch mass and survivorship in females and a negative effect in others [147]. These differences could be explained by a quadratic relationship between corticosterone and fitness [146]. A reduced corticosterone level may indicate acclimatization allowing individuals to maintain good body condition and will not be sufficient to produce a stress-mediated phenotype to cope with a novel environment and consequently suffer lower survival.…”

Hair cortisol levels determined at different body sites in the New Zealand White rabbit

“…Cortisol is usually determined in samples of blood (Szeto et al, 2004;de Prada et al, 2007;Cabezas et al, 2007), faeces (Szeto et al, 2004), urine (Walker et al, 2007), milk (Gygax et al, 2006) and saliva (Negrao et al, 2004). Cortisol measurements over a longer period of time, weeks or months, can be taken in hair samples.…”