THE EFFECTS OF AUDITORY PREDATION RISK CUES ON CATERPILLAR GROWTH, DEVELOPMENT, AND FITNESS

Abstract

Predation risk is a major factor that impacts the growth and behavior of organisms. Being able to detect potential predators before contact offers a major competitive advantage, but these anti-predator behaviors often come with a significant energetic cost. Domestication, which can remove predation stress as a selective force, can lead to a reduction in these costly anti-predator behaviors in favor of increased growth and reproduction. Monarch (Danaus plexippus) and spongy moth (Lymantria dispar dispar) caterpillars both use auditory cues as a primary detection method for airborne predators. We exposed both species to a series of auditory cues in order to elicit anti-predator behavior and quantify the fitness costs of said behaviors in the absence of actual predation. In the case of L. dispar, we compared the reactions of domesticated and wild larvae to determine the effects of domestication on their response to predation cues. D. plexippus caterpillars displayed shorter time to pupation and lower pupal weight when exposed to predator cues, implying that they accelerate their development and pupate more quickly to escape the risk of predation. This accelerated development leads to the caterpillars pupating at a lower weight, potentially reducing their fecundity and overall ecological fitness. When exposed to auditory predator cues, wild-type L. dispar larvae suffered increased mortality, while domesticated caterpillars showed no such response. This suggests a loss of predation risk sensitivity following domestication, the first to be found in an insect species.