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.