Mid-flight prey switching in the fringed-lipped bat (Trachops cirrhosus)

Due to their influence on the evolution of the signaling behavior and the structure of signals used by prey, the foraging strategies of eavesdropping predators have been the focus of considerable research attention. Many prey signal from aggregations, however, and predators already en route to attack one individual often encounter the signals of other prey nearby. Little attention has been paid to if and how predators integrate this information into their foraging decisions. We used playback experiments with wild-caught fringed-lipped bats (Trachops cirrhosus) to test whether these predators act on new information to switch foraging decisions mid-approach, and examined how switching influenced the effectiveness of their attacks. We found that on nearly 80% of attack flights, bats switched between identical túngara frog (Engystomops pustulosus) calls positioned in close proximity (1m apart). This switching rate dropped to 55% when prey were separated by 3 m. The accuracy of attacks improved when bats switched between calls spaced 1m apart, but the localization advantage of switching disappeared for calls separated by 3m. Regardless of whether bats switched to attack new targets, localization errors increased, flight times increased, and capture success decreased for bats exposed mid-flight to the calls of prey spaced at the larger distances. In the case of flight times, this appears to be due to a distraction effect when experiencing calls 3m from the initial target. Overall, our results reveal that fringed-lipped bats attend cues from non-targeted prey during attack flights, and that the distance between calling prey alters the effectiveness of attacks, regardless of whether a bat switches targets. Understanding how eavesdropping predators update their foraging decisions in response to new signals from neighboring prey will lead to a fuller picture of the ways these unintended receivers shape the evolution of signaling behavior.

Methods
Phonotaxis trials in a flight cage were conducted with wild-caught bats. Full methods are described in the associated manuscript.