Foraging strategy mediates ectotherm predator–prey responses to climate warming

Abstract

Climate warming and species traits interact to influence predator performance, including individual feeding and growth rates. However, the effects of an important trait—predator foraging strategy—are largely unknown. We investigated the interactions between predator foraging strategy and temperature on two ectotherm predators: an active predator, the backswimmer Notonecta undulata, and a sit‐and‐wait predator, the damselfly Enallagma annexum. In a series of predator–prey experiments across a temperature gradient, we measured predator feeding rates on an active prey species, zooplankton Daphnia pulex, predator growth rates, and mechanisms that influence predator feeding: body speed of predators and prey (here measured as swimming speed), prey encounter rates, capture success, attack rates, and handling time. Overall, warming led to increased feeding rates for both predators through changes to each component of the predator’s functional response. We found that prey swimming speed strongly increased with temperature. The active predator’s swimming speed also increased with temperature, and together, the increase in predator and prey swimming speed resulted in twofold higher prey encounter rates for the active predator at warmer temperatures. By contrast, prey encounter rates of the sit‐and‐wait predator increased fourfold with rising temperatures as a result of increased prey swimming speed. Concurrently, increased prey swimming speed was associated with a decline in the active predator’s capture success at high temperatures, whereas the sit‐and‐wait predator’s capture success slightly increased with temperature. We provide some of the first evidence that foraging traits mediate the indirect effects of warming on predator performance. Understanding how traits influence species’ responses to warming could clarify how climate change will affect entire functional groups of species.

Thermal evolution ameliorates the long‐term plastic effects of warming, temperature fluctuations and heat waves on predator–prey interaction strength

“…In line with expectations (Sentis et al., 2012, 2015; Thompson, 1978; Twardochleb et al., 2020), also the handling time was strongly dependent on temperature. Handling times are mainly determined by digestion time (hence physiology) and the actual time of handling when killing and eating a prey (Sentis et al, 2013b).…”

“…As can be expected for ectotherm predators, the functional response parameters were affected by the thermal treatments (Sentis et al., 2012; Thompson, 1978; Twardochleb et al., 2020). Notably, while 4°C warming did not influence the search rates of high‐latitude larvae, it decreased those of low‐latitude larvae.…”

“…This contrasts with the pattern of latitude‐associated thermal adaptation as we found for growth rate (Appendix B). Different relationships between search rate and temperature have been recorded: positive (Petchey et al., 2010; Thompson, 1978; Twardochleb et al., 2020), negative (Grigaltchik et al., 2012), from positive to negative (Englund et al., 2011; Sentis et al., 2012) and no effect (Sentis et al., 2015). Our results may suggest that the thermal reaction curve of low‐latitude predator search rates is in the decreasing phase of the quadratic Arrhenius model where biotic reaction rates decrease with temperature above the thermal optimum, a pattern detected in a meta‐analysis on search rates by Englund et al.…”

“…Search rates of predators may first increase with increasing temperatures when the metabolic rate is high enough to boost bioenergetic activities related with foraging, but then decrease with temperature when metabolic rates decrease by the stronger influence of catabolism (Sentis et al., 2012). A recent study found that the capture success of another damselfly decreased at temperatures above the environmental mean (Twardochleb et al., 2020). This may not have led to an increased foraging effort because metabolic demands did not increase under warming as suggested by the constant metabolic rates.…”

Warming and Predation Alter Consumer Coexistence

“…This caused a signi cant ampli ed interaction of warming and predation on the growth and reproduction of R. swinhoei. Warming has also shown to affect attack rate, handling time and predation success (Twardochleb et al 2020). However, in our study, the prey are rather slow-moving species, the impacts of warming on the predation was mainly determined by the increased feeding rate, and the prey are unlikely to develop strongly avoidant mechanisms against predation in one or two generations.…”