Exploiting vulnerable prey: Moths and red bats (Lasiurus borealis; Vespertilionidae)

We observed 18 individually banded red bats, Lasiurus borealis, foraging around streetlights to test our hypotheses that they were either foraging cooperatively or practising kleptoparasitism (theft of prey). In 80 of 238 attacks, bats reattacked the same moth (29% of these attacks involved >1 bat and 71% just 1 bat). Logistic regression showed that a bat's foraging-success rate was significantly positively affected by the number of attacks made on a moth (p < 0.05) and the type of attack (by a single bat versus >1 bat) (p < 0.05) but negatively affected by the length of time over which the moth was attacked (i.e., from the first to the second attack) (p < 0.05). Using a model we tested whether or not an eavesdropping L. borealis could be in a position to reattack a vulnerable (previously attacked) moth before the initial attacker and found that if an eavesdropper was within 30 m during the first attack it could always beat the first attacking bat to the vulnerable moth. The data and analysis support neither the cooperative-foraging nor the kleptoparasitism hypotheses, but rather show that a combination of timing of moth defensive behaviour and bat flight performance strongly influences the outcome of an attack.