R code and data for the publication "Predators minimize energy costs, rather than maximize energy gains under warming: Evidence from a microcosm feeding experiment"

Abstract: <strong>1.</strong> Climate warming may alter predator-prey interactions and predator feeding behaviour due to increased metabolic demands. How predators meet these increased demands may depend on trade-offs in prey energy content and body size, handling time, and other functional constraints. <strong>2.</strong> We tested hypotheses associated with these trade-offs with the predatory mite <em>Stratiolaelaps scimitus</em>, and three prey that differed in body size, energy content, and defenses (<em>Folsomia candida</em>, <em>Oppia nitens</em>, and <em>Carpoglyphus lactis</em>). We estimated metabolic rate, predation in choice and no choice feeding trials, movement rate, and lipid and protein content for all four species at 16 °C and 24 °C. We used these data to estimate the predator’s energy demands and compared these to estimated energy intake in the choice feeding trials. <strong>3.</strong> Predators had greater metabolic demands at 24 °C than at 16 °C, but temperature did not affect predator or prey movement rates. Warming decreased lipid content, but not protein content, of all three prey species, leading to lower energy content for <em>C</em>. <em>lactis</em> and <em>O. nitens</em>, but not <em>F</em>. <em>candida</em>. In both feeding trials at 24 °C, predators increased their feeding on the smaller, energy-poor <em>C</em>. <em>lactis</em>, but not the larger, energy-rich <em>F</em>. <em>candida</em>, resulting in lower estimated energy intake. <em>S</em>. <em>scimitus</em> did not feed on <em>O. nitens</em> at either temperature. <strong>4.</strong> Predators increasingly fed on small-bodied prey under warming, and not the large-bodied prey despite the potential for greater energetic gains from larger prey. We posit that predators minimized energy lost during feeding through lower handling costs associated with <em>C. lactis</em>, rather than maximize energy gain. We conclude that selection of prey based on body size changes with temperature as a trade-off for predators to balance increased metabolic demands. As predators provide top-down control and regulate energy flow through the consumption of their prey, changes to predator feeding behaviour with climate warming may affect food web dynamics and ecosystem-level processes.