The complex effect of illumination, temperature, and thermal acclimation on habitat choice and foraging behavior of a pit-building wormlion

Abstract

Habitat selection has consequences for an animal’s fitness, especially for sit-and-wait predators with limited mobility, and which cannot always correct earlier suboptimal choices. Environmental change may nevertheless lead individuals to relocate to another site, although such relocations can be energetically costly or risky. Temperature and illumination are two important factors that undergo change in seasonal and daily cycles that may impact habitat quality. Animals must therefore either acclimate to the new conditions or relocate. Wormlions are sit-and-wait, trap-building predators whose success in foraging is highly dependent on their surroundings. Here, we manipulated temperature (high, low, and moderate) and let the wormlions choose between lit and shaded conditions. We found that the typical wormlion preference for shaded microhabitats decreased with increasing temperature. We then followed wormlion behavior under a full-factorial design of two constant illumination conditions (light vs. shade) and three temperatures. Although both constant light and high temperature reduced foraging performance, expressed in pit construction tendency and pit area, the two conditions had a non-additive effect. Acclimation to extreme thermal conditions moderated the negative effects of such temperatures, expressed in a higher tendency to construct a pit, and equalized performance across temperatures. Finally, the high temperature reduced behavioral consistency while acclimation increased it, suggesting that consistency is impaired by unfavorable environmental change. To conclude, while an environmental change usually affects several environmental factors simultaneously, the induced behavioral change is neither synergic nor additive and can even differ from the response to each unfavorable environmental factor in isolation. Choosing a suitable habitat is essential for survival and reproduction, especially for sedentary organisms, and requires the consideration of various environmental conditions. Acclimating to suboptimal conditions, however, might conduce to improving performance in a less suitable habitat. Testing the effect of several environmental conditions on habitat choice and foraging behavior, before and after acclimation, has rarely been carried out. Here, we tested the combined effects of temperature, illumination, and their interaction, on habitat choice and foraging performance of a sit-and-wait predator, the wormlion. Wormlions usually prefer shade, but their preference for light increases with decreasing temperature. Both temperature and illumination affect behavior but their joint effect is not additive. Acclimation, which took place for temperature but not for illumination, improved certain foraging behaviors. Our findings highlight the importance of evaluating several environmental conditions and behaviors when studying habitat choice and foraging behavior.