Evidence for Exploitative Competition: Comparative Foraging Behavior and Roosting Ecology of Short-Tailed Fruit Bats (Phyllostomidae)

Chestnut short-tailed bats, Carollia castanea , and Seba's short-tailed bats, C. perspicillata (Phyllostomidae), were radio-tracked ( N = 1593 positions) in lowland rain forest at Tiputini Biodiversity Station, Orellana Province, Ecuador. For 11 C . castanea , mean home range was 6.8 ± 2.2 ha, mean core-use area was 1.7 ± 0.8 ha, and mean long axis across home range was 438 ± 106 m. For three C . perspicillata , mean home range was 5.5 ± 1.7 ha, mean core-use area was 1.3 ± 0.6 ha, and mean long axis was 493 ± 172 m. Groups of less than five C. castanea occupied day-roosts in earthen cavities that undercut banks the Tiputini River. Carollia perspicillata used tree hollows and buildings as day-roosts. Interspecific and intraspecific overlap among short-tailed bats occurred in core-use areas associated with clumps of fruiting Piper hispidum (peppers ) and Cecropia sciadophylla . Piper hispidum seeds were present in 80 percent of the fecal samples from C . castanea and 56 percent of samples from C . perspicillata . Carollia perspicillata handled pepper fruits significantly faster than C . castanea ; however, C . castanea commenced foraging before C . perspicillata emerged from day-roosts. Evidence for exploitative competition between C . castanea and C . perspicillata is suggested by our observations that 95 percent of ripe P . hispidum fruits available at sunset disappear before sunrise ( N = 74 marked fruits). Piper hispidum plants produced zero to 12 ripe infructescences per plant each night during peak production. Few ripe infructescences of P . hispidum were available during the dry season; however, ripe infructescences of C . sciadophylla , remained abundant.