The non-consumptive effects of predators on prey are wide-spread and decrease multiple aspects of prey performance and fitness. While there is a rich body of literature on prey responses to predators and the consequences for populations and communities. These effects have widely been assumed, however, to be sub-lethal. We examined responses of a larval odonate, Leucorrhinia intacta (Anisoptera:Libellulidae) to caged predators (fish and invertebrates) including measuring the effects of non-consumptive predators on survival. In subsequent work we tested one hypothesis for how non-consumptive predators might affect survival in prey organisms, through reducing allocation to immune function. This mechanism might explain the observed increase in non-consumptive, predator induced mortality.
Results/Conclusions
In our experiments on the effects of the perception of predation risk on odonate larvae, we found that the presence of predators prevented from consuming larvae resulted in increased mortality in larval L. intacta. Exposure to caged fish also increased the rate of metamorphic failure in animals that had survived the larval stage. Surprisingly, in these experiments exposure to predators was not associated with smaller body sizes in surviving larvae or adults, nor changes in adult morphology. Contrary to our expectations we found that larvae exposed to invertebrate predators had stronger immune responses in the presence of caged predators. This has opened up a number of new questions about interactions between predation stress and immunity and we discuss future directions in this research.