Species-specific strategies increase unpredictability of escape flight in eared moths

ABSTRACT Many prey animals form mixed-species groups. Mixed-species groups provide various benefits ranging increased food intake to increased chance of predator detection. The escape-tactic diversity hypothesis predicts another benefit. It postulates that the overall unpredictability of evasive movement is increased if multiple species with different evasive tactics mix, resulting in enhanced predator protection for the whole group. Echolocating bats and eared moths are a textbook example of predator-prey interactions. Moths exhibit evasive flight with diverse tactics; however, the variability of their evasive flight within and between species has never been systematically quantified. We therefore recorded flight strength of eight moth species in response to the same level of simulated bat predation. We show species-specific and size-independent differences in both overall flight strength and in change of flight strength over time, confirming the escape-tactic diversity hypothesis for eared moths. Additionally, we show strong inter-individual differences in evasive flight within some species. This diversity in escape tactic between eared moths increases the overall unpredictability of their evasive flight in mixed-species groups, likely providing better protection against predatory bats for the single individual.