Host plants as prey defense signals

Aposematic, or warning, coloration is thought to facilitate predator avoidance behavior of defended prey. This effect benefits both experienced predators on an individual level and prey on a population level. However, theory predicts a transitional period between aposematic and more cryptic phenotypes, in which prey are defended but lack warning coloration. Here we propose that environmental stimuli closely associated with defended prey can serve as warning signals during this transitional period. Specifically, we asked whether prey host plants could serve as sufficient stimuli to facilitate predator learning, and as a direct effect, prey survival. We achieved this by assigning chemically defended and undefended Lepidopteran larvae to different host plant species. Larvae were manipulated to look morphologically identical and were exposed to wild-caught, captive Carolina Wrens (Thryothorus ludovicianus). We observed over a learning trial and an experienced trial, the number of returns to plant species hosting defended vs. undefended larvae and recorded the number of each larvae type consumed. Our results showed a significant effect on both the number of returns to host plant species and which prey were consumed, with simulated downstream effects on population phenotypic frequency.