The influence of bat predation on calling behavior in neotropical forest katydids (Insecta: Orthoptera: Tettigoniidae).

In many animals, members of one sex advertise themselves using acoustic, visual, or chemical cues in order to attract mates. These signals are usually species specific and highly localizable, which helps them function successfully in a mating context, but also means they can be used by predators. How animals resolve the conflict between attracting mates and predators is an intriguing question that has received little attention in the literature.

This study examines a predator-prey system in which acoustically orienting foliage gleaning bats (FGB) in a lowland forest on Barro Colorado Island, Panama, are attracted to the airborne songs of katydids in the subfamily Pseudophyllinae. Aspects of katydid call production that lessen predation by FGB were also studied.

During two years, field and flight cage experiments showed that members of four species of forest-dwelling FGB can use katydid songs to locate these insects as prey. A study of their echolocation calls shows that they are typical of bats that forage in cluttered environments, and probably do not allow the animals producing them to locate insects on foliage. At least one FGB, Micronvcteris hirsuta, was a major katydid predator, and took insects inhabiting the forest understory that were active in the early evening when bats foraged most actively.

Airborne calling songs were recorded from members of 17 pseudophylline species sympatric with FGB. With one exception, their calls were short, sporadically produced and emphasized high audio or ultrasonic carrier frequencies. In flight cage experiments, these calls were more difficult for FGB to localize than were the longer and more frequently produced broadband calls that are typical of katydids in areas without FGB. The exception, Ischnomela pulchripennis , sang from large, spine-covered terrestrial bromeliads, which protect it from predation by FGB.

The pseudophyllines studied supplemented their short inconspicuous calls with "tremulations, " substrateborne signals that travel from one individual to another through plants but are inaccessible to acoustically orienting predators like FGB. Tremulations appear to be the rule rather than the exception in tropical New World katydids that are sympatric with FGB. They represent the first report of widespread behavioral anti-bat defenses in katydids