Stress and Demographic Decline: A Potential Effect Mediated by Impairment of Reproduction and Immune Function in Cyclic Vole Populations

Abstract

The stress response is initially adaptive, operating to maintain homeostasis. However, chronic long-term exposure to stressors may have detrimental effects. We proposed that chronic stress may be a major factor in demographic vole cycles, inducing decline in high-density populations. We monitored four populations of the fossorial water vole Arvicola scherman, which undergo pluriannual demographic cycles in the Jura Mountains (France). Sampling was conducted during the high densities and the decline. We measured fecal corticosterone metabolites (FCMs) to assess stress levels and injected phytohemagglutinin to estimate the cell-mediated immune response. We demonstrated that stress levels increase between the high densities and the decline in most of the vole populations. At the individual level, FCM concentrations varied with reproductive status and body condition. During the outbreak, we observed significantly higher levels of FCM concentrations in nulliparous females than in females that had previously reproduced. Moreover, a significant negative correlation was observed between concentrations of FCMs and both immunocompetence and body condition during population decline. These results might reflect an impairment of the female reproductive capability in high densities and accelerated senescence affecting immune function during decline, both arising from chronic stress.

Negative relationships between cellular immune response, Mhc class II heterozygosity and secondary sexual trait in the montane water vole

“…1995). Spatio‐temporal variations in vole abundances have been described in a previous study for these localities (Charbonnel et al. 2008a).…”

“…One person carried out all injections and thickness measurements. Part of these data has previously been published (Charbonnel et al. 2008a).…”

From process to pattern: how fluctuating predation risk impacts the stress axis of snowshoe hares during the 10-year cycle

“…Boonstra et al (1998a) also found that hares in winter were more stressed during the decline phase when predator numbers were greatest than during the late low phase when they were the lowest. Charbonnel et al (2008) also found that cyclic populations of water voles, Arvicola scherman, were more stressed during the decline phase compared with the peak. Additionally, an increase in the number of predators has been shown to increase glucocorticoid (GC) levels in a number of other non-cyclic freeranging mammals and birds (Silverin 1997;Hik et al 2001;Scheuerlein et al 2001).…”

Glucocorticoid Stress Responses of Reintroduced Tigers in Relation to Anthropogenic Disturbance in Sariska Tiger Reserve in India

“…Glucocorticoids (cortisol and corticosterone) are released under stressful conditions to help the organism defend itself against a perceived stressor [22]. Although the short term release of these hormones is known to increase fitness via energy mobilization, prolonged periods of high glucocorticoid concentrations are known to decrease fitness by affecting reproductive success, immuno-suppression, growth, and muscular atrophy [23–26]. Long-term anthropogenic disturbance has been shown to increase glucocorticoid levels in many wildlife taxa, e.g.…”