Short- and long-term behavioural, physiological and stoichiometric responses to predation risk indicate chronic stress and compensatory mechanisms

Abstract

Prey organisms are expected to use different short- and long-term responses to predation risk to avoid excessive costs. Contrasting both types of responses is important to identify chronic stress responses and possible compensatory mechanisms in order to better understand the full impact of predators on prey life history and population dynamics. Using larvae of the damselfly Enallagma cyathigerum, we contrasted the effects of short- and long-term predation risk, with special focus on consequences for body stoichiometry. Under short-term predation risk, larvae reduced growth rate, which was associated with a reduced food intake, increased metabolic rate and reduced glucose content. Under long-term predation risk, larvae showed chronic predator stress as indicated by persistent increases in metabolic rate and reduced food intake. Despite this, larvae were able to compensate for the short-term growth reduction under long-term predation risk by relying on physiological compensatory mechanisms, including reduced energy storage. Only under long-term predation risk did we observe an increase in body C:N ratio, as predicted under the general stress paradigm (GSP). Although this was caused by a predator-induced decrease in N content, there was no associated increase in C content. These stoichiometric changes could not be explained by GSP responses because, under chronic predation risk, there was no decrease in N-rich proteins or increase in C-rich fat and sugars; instead glycogen decreased. Our results highlight the importance of compensatory mechanisms and the value of explicitly integrating physiological mechanisms to obtain insights into the temporal dynamics of non-consumptive effects, including effects on body stoichiometry.

The Temperature Dependence of Predation Stress and Prey Nutritional Stoichiometry

“…Hence, the experimental outcome could be consistent with, but a generalization of, the original idea of the effects of predation stress on organismal stoichiometry (Hawlena and Schmitz, 2010a). Third, our results may also help offer clues as to why results of studies that tested for the effects of predation stress on nutrient intake by ectothermic species were counter to original predictions (Thaler et al, 2012;Costello and Michel, 2013;Dalton and Flecker, 2014;Kaplan et al, 2014;Guariento et al, 2015;Kirschman et al, 2016;Van Dievel et al, 2016). The higher N intake by Risk prey than by No Risk prey observed in these studies has been attributed to developmental needs that facilitate prey escape from predation.…”

“…Several studies experimentally examining the interplay between temperature and predation risk have provided mixed support for the original idea that rising temperature should exacerbate predation stress causing prey to consume more C (Jansens et al, 2015;Kirschman et al, 2016;Van Dievel et al, 2016;Zhang et al, 2016). These studies used 2 × 2 factorial designs that crossed a temperature treatment with a perceived predation risk treatment.…”

“…It involves stress responses that, when chronic, can lead to persistent physiological changes like elevated metabolic rate (Beckerman et al, 2007;Slos and Stoks, 2008;Hawlena and Schmitz, 2010a;Zanette et al, 2011;Thaler et al, 2012;Clinchy et al, 2013;Van Dievel et al, 2016). This is an adaptive coping mechanism (Hawlena and Schmitz, 2010a).…”

“…Some experiments have shown that such shifts in nutrient intake and body stoichiometry can indeed occur between conditions with and without perceived predation risk (McPeek et al, 2001;Hawlena and Schmitz, 2010b;Jansens et al, 2015). Other experiments have, however, shown that the predicted responses do not occur (Costello and Michel, 2013;Dalton and Flecker, 2014;Kaplan et al, 2014;Guariento et al, 2015;Kirschman et al, 2016;Van Dievel et al, 2016;Zhang et al, 2016), thereby calling into question the generality of the predicted stress response.…”

Training for Translocation: Predator Conditioning Induces Behavioral Plasticity and Physiological Changes in Captive Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) (Cryptobranchidae, Amphibia)

“…Stimuli such as stochastic weather conditions, contaminants, pathogens, and predators are novel to captive-reared animals and can magnify the stress of translocations [1,[4][5][6]. Increased stress is correlated with reduced reproductive potential, increased disease susceptibility, altered energy expenditure, irregular dispersal movements, and increased predation risk [7,8]. Subsequently, stress (in a variety of forms) is a leading cause of translocation mortality [1][2][3]9,10].…”