THE ROLES OF ECHOLOCATION AND OLFACTION IN 2 NEOTROPICAL FRUIT-EATINGBATS, CAROLLIA-PERSPICILLATA AND C-CASTANEA, FEEDING ON PIPER

We studied the echolocation and foraging behavior of two Neotropical f rugivorous leaf-nosed bats (Carollia perspicillata, C. castanea: Phyll ostomidae) in a flight cage. To test which cues Carollia uses to detec t, identify, and localize ripe Piper fruit, their preferred natural fo od, we conducted experiments under seminatural conditions with ripe, u nripe, and artifical fruits. We first offered the bats ripe fruits and documented their foraging behavior using multiflash stereophotography combined with simultaneous sound recordings. Both species showed a si milar, stereotyped foraging pattern. In search flight, the bats circle d through the flight cage in search of a branch with ripe fruit. After finding such a branch, the bats switched to approach behavior, consis ting of multiple exploration flights and the final approach when the b ats picked up the fruit at its tip and tore it off in flight. Our beha vioral experiments revealed that odor plays an important role in enabl ing Carollia to find ripe fruit. While foraging, Carollia always echol ocated and produced multiharmonic, frequency-modulated (FM) signals of broad bandwidth, high frequency, short duration, and low intensity. W e discriminated an orientation phase (mostly a single pulse per wingbe at) and an approach phase (groups of two to six pulses per wing beat). We conclude from the bats' behavioral reaction to real and artificial fruit as well as from characteristic patterns in their echolocation b ehavior that during exploration flights, Carollia changes from primari ly odor-oriented detection and initial localization of ripe fruit to a primarily echo-oriented final localization of the position of the fru it.