Predation risks of signalling and searching: bats prefer moving katydids

Males signalling their attractiveness to females are at risk from
predators that exploit mating signals to detect and locate prey.
Signalling, however, is not the only risky activity in sexual
interactions: mate searching can incur risk as well. Male Neotropical
pseudophylline katydids produce both acoustic and vibrational signals
(tremulations). Females reply to male signals with tremulations of their
own, and both sexes walk to find one another. We asked if movement
increases predation risk, and whether tremulation or walking was more
attractive to predators. We offered the Neotropical gleaning bat
Micronycteris microtis a series of two-choice tests, presenting the bats
with katydid models that were motionless or moved in a way to mimic either
tremulating or walking. We found that prey movements do put prey at risk.
Although M. microtis can detect motionless prey on leaves, they preferred
moving prey. Our study shows that movement can put searching or signalling
prey in danger, potentially explaining why silent female katydids are
frequently consumed by gleaning bats.