Compensatory mechanisms for ameliorating the fundamental trade-off between predator avoidance and foraging

Abstract

Most organisms face the problem of foraging and maintaining growth while avoiding predators. Typical animal responses to predator exposure include reduced feeding, elevated metabolism, and altered development rate, all of which can be beneficial in the presence of predators but detrimental in their absence. How then do animals balance growth and predator avoidance? In a series of field and greenhouse experiments, we document that the tobacco hornworm caterpillar, Manduca sexta, reduced feeding by 30-40% owing to the risk of predation by stink bugs, but developed more rapidly and gained the same mass as unthreatened caterpillars. Assimilation efficiency, extraction of nitrogen from food, and percent body lipid content all increased during the initial phase (1-3 d) of predation risk, indicating that enhanced nutritional physiology allows caterpillars to compensate when threatened. However, we report physiological costs of predation risk, including altered body composition (decreased glycogen) and reductions in assimilation efficiency later in development. Our findings indicate that hornworm caterpillars use temporally dynamic compensatory mechanisms that ameliorate the trade-off between predator avoidance and growth in the short term, deferring costs to a period when they are less vulnerable to predation.antipredator behavior | nonconsumptive effects | predator-prey interactions | phenotypic plasticity F eeding is dangerous (1, 2). For many animals, reduced feeding is a common response to the watchful eyes of predators that exploit movement as a primary prey location cue (3, 4). In addition, metabolic rate typically increases in response to predation risk (5), potentially exacerbating the costs of reduced food intake. Organisms respond to predation risk and the corresponding food limitation through phenotypically plastic responses, including behavioral, physiological, and developmental changes (6-9). The integration of these factors to ameliorate the impacts of predator exposure has been little studied, however, especially over development during periods of chronic predation risk (10).After a period of food limitation and associated decreased growth (11, 12), many organisms increase growth through compensatory responses (13-15). Compensation after starvation can be achieved via increased consumption, increased metabolic or digestive efficiency, or altered developmental rate when food becomes available (16). Because predation risk is an important natural phenomenon that constrains foraging and induces physiological stress, compensatory mechanisms may be especially important in this context. Nonetheless, compensatory responses to predation risk, and their behavioral, physiological, and developmental underpinnings, are not well understood (17). Much of the research on responses to predator exposure has focused on behavioral changes in resource selection, where generalist foragers, such as elk and grasshoppers, switch habitat and diet use in the presence of predators (18,19). Little is known about physiological respon...

Predator‐driven elemental cycling: the impact of predation and risk effects on ecosystem stoichiometry

“…Some species compensate for risk by decreasing foraging effort and by altering food passage rate and assimilation, resulting in altered efficiency of N assimilation (Thaler et al. 2012; Dalton and Flecker 2014). Other species respond by enhancing N consumption and allocating it to build more musculature related to escape morphology (Costello and Michel 2013).…”

“…2011; Thaler et al. 2012; Clinchy et al. 2013), that changes in herbivore metabolic rate due to predation stress does not rise monotonically, but rather jumps discontinuously to a higher level (e.g., 45% difference between stress and stress‐free conditions [Hawlena and Schmitz 2010a]).…”

Impacts of metformin and aspirin on life history features and longevity of crickets: trade-offs versus cost-free life extension?

“…Compensatory increases in assimilation efficiency allowed caterpillars to maintain growth despite reduced foraging under predation risk (but costs emerged at later ages; Thalera et al 2012). Organisms have considerable Bcompensatory scope^to increase feeding and metabolism to offset elevated costs (Rollo 1994).…”

Sublethal Doses of Insecticides Affect the Fecundity and Fertility of the <i>Chrysodeixis includens</i>?

“…The concentrations (CL 25 and CL 50 ) obtained in the previous bioassay were used to characterize the sublethal effects of insecticides on C. includens and compared to a control (water). The bioassay was performed and conducted according to the methodology described by [13].…”

“…The caterpillars, which after physical stimulation with the tweezers in the prothorax region showed no movement, were considered dead. Lethal concentrations (CL 25 and CL 50 ) were estimated using the Probit routine with the statistical program SAS Version University Edition [14].…”