Hot and scared: how do heatwaves and predation risk impact resource acquisition and allocation?

Abstract

Heatwaves are increasingly prevalent and can constrain investment into important life-history traits. In addition to heatwaves, animals regularly encounter threats from other organisms in their environments, such as predators. The combination of these two environmental factors introduces a decision-making conflict—heat exposure requires more food intake to fuel investment into fitness-related traits, but foraging in the presence of predators increases the threat of mortality. Thus, we used female variable field crickets ( Gryllus lineaticeps ) to investigate the effects of heatwaves in conjunction with predation risk (exposed food and water sources, and exposure to scent from black widow spiders, Latrodectus hesperus ) on resource acquisition (food intake) and allocation (investment into ovarian and somatic tissues). A simulated heatwave increased food intake and the allocation of resources to reproductive investment. Crickets exposed to high predation risk reduced food intake, but they were able to maintain reproductive investment at an expense to investment into somatic tissue. Thus, heatwaves and predation risk deprioritized investment into self-maintenance, which may impair key physiological processes. This study is an important step towards understanding the ecology of fear in a warming world.