BONACCORSO: A PANAMANIAN BAT COMMUNITY


GLEANING CARNIVORE GUILD
 BODY SIZE.-The largest feeding guild within the bat fauna of BCI,
the gleaning carnivore guild, consists of nine phyllostomine species
which exhibit the largest range in body size in any of the feeding guilds
(Table 13). Micronycteris megalotis, one of the smallest bats on the
island, has a mean body weight of 6.3 g, while Vampyrum spectrum,
the largest species, weighs about 120 g.
 FOOD SPECIES SELECTION.-Except for the vertebrate diet of V.
spectrum, guild members feed predominantly on insects; however,
fruits, pollen, arachnids, or lizards supplement the diet of various
species. The collected fecal samples from these species are now being
analyzed and will be published elsewhere.
 Novick (1971) hypothesized that large-eared insect- and vertebrate-
eating bats, such as the species in this gleaning carnivore guild, are
adapted to distinguish and capture prey items resting on foliage by
echolocation. Recent information cited below demonstrate that olfac-
tion and sound produced by prey are used by some of these bats to find
prey.
 Ross (1967), Wilson (1971b), and Vehrencamp et al. (1977) have
shown that many large-eared bats do feed primarily by gleaning large
insects and birds that nocturnally perch on vegetation or on the
ground. Gardner's (1977) review of the food habits of bats in this guild
further confirms that food items such as lizards and large insects are
gleaned from foliage.
 MICRONYCTERIS. Wilson (1971b) reported that large roaches, or-
 thopterans, and scarabeid beetles are the most important items in the
 diet of M. hirsuta on Orchid Island, a small island adjacent to BCI.
 During the dry season fruit became an important component of the
 diet of this species as indicated by droppings below the study roost.
 My data show that M. megalotis and M. brachyotis also switch in part

 TABLE 13.-WEIGHTS IN GRAMS OF GLEANING CARNIVORES. COLUMN HEADINGS ARE
 DEFINED IN TABLE 1.
 Bat species X S.D. N Wgt/Wgt,~
 M. megalotis 6.3 0.6 6 O
 M. brachyotis 9.7 1.1 3 1.53
 M. crenulatum 14.7 0.7 12 1.52
 M. hirsuta 15.2 1.2 7 1.03 (1.57*)
 T. cirrhosus 31.0 3.8 13 2.09
 T. sylvicola 32.6 3.6 10 1.04
 T. bidens 35.6 2.3 7 1.09
 P. hastatus 91.2 4.0 7 2.56
 V. spectrum 120.0 1 1.31
 *Ratio between weights of Al hirsluta and M. hrachyotis.