Responses to alarm chemicals from injured prey may influence predation risk and foraging success of receivers and senders, while learning can influence the strength of these responses. Thus, it is important to know when in ontogeny prey produce and detect alarm substances and how learning shapes their response, but surprisingly little is known about either of these topics. We assessed when in the life of red-spotted newts, Notophthalmus viridescens, alarm chemicals are produced and detected by comparing adult versus eft (terrestrial juveniles) and larval responses to rinses and tissue extracts from individuals in each life-history stage. To evaluate the influence of experience in larvae exposed to conspecific alarm substances and rinses from adults known to cannibalize larvae, we compared the response of naive larvae, which had no prior experience with alarm chemicals or predators, to experienced larvae, which were likely to have experienced alarm chemicals and predators in their native pond. Larvae were indifferent to larval rinses and extracts, but reduced their activity in response to adult rinses and extracts. There was no difference between responses of recently hatched naive and experienced larvae, indicating that larvae exhibit innate antipredator behaviors in response to adult odour. Adults were indifferent to all larval treatments and adult rinse, but avoided adult extract. Since neither adults nor larvae responded to larval extract, larvae did not appear to possess alarm chemicals, and consequently, we were unable to assess the influence of experience on alarm substance response in larvae. Adults and efts were indifferent to rinses, but avoided extracts from conspecifics of both life-history stages. Together, these results demonstrate that red-spotted newts do not produce alarm chemicals until late in larval development, but can respond to predation-related chemical cues soon after hatching
