BONACCORSO: A PANAMANIAN BAT COMMUNITY


 Temporal partitioning of the access to a resource may arise when
the resource is concentrated in a small space. Fruiting trees visited by
canopy frugivores tend to be few or moderate in numbers of in-
dividuals, but very large per individual. Each individual tree produces
thousands of fruits. Temporal differences in flight (and feeding) times
between similar-sized species that feed in the same trees is a means to
avoid behavioral interference between species when the food supply is
abundant in amount but limited in spatial distribution.
 The foraging strategies of fruit bats should optimize the intake of
energy with respect to the density, abundance, spatial distribution,
and particle sizes of available bat fruits. Moist forest sites throughout
Central America usually contain 8 to 10 species of canopy frugivores
(pers. obs.). Eight species of stenodermine bats form the canopy
frugivore guild on BCI. These bats feed almost entirely on fruits grow-
ing in the forest canopy on trees, vines, and epiphytes. Individuals of
most of these plants occur at very low densities and in patchy distribu-
tions within the forest. Most canopy trees producing bat fruits are
large enough to feed hundreds of bats per night during their fruiting
periods of about a week. Because a great range in size of preferred
canopy fruits is available, it is possible for many bat species to
specialize in taking food particles of different sizes. Seven species on
BCI are fig specialists that partition figs primarily on the basis of size.
The other species is a generalist with regard to the type of fruit in its
diet.
 The fig specialists appear to have large home ranges (about 3 km2
 for A. jamaicensis) compared to other bats of similar size, and travel
 through much of the home range in a night to obtain widely scattered
 food resources (Heithaus et al. 1974, Morrison 1978, Bonaccorso, un-
 publ. data). Artibeus phaeotis, the fruit generalist, appears to have a
 comparatively small home range for its size, probably because it feeds
 on more kinds of fruits and thus is more likely to encounter a suitable
 food resource in a smaller area than a specialist.
 Frugivorous bats consume their own weight in fruit per night (Mor-
 rison 1978), because they appear to have low assimilation efficiencies
 and high metabolic rates (McNab 1969). Each bat must make about
 eight to a dozen visits to one or a few resource trees per night (Mor-
 rison 1978, in press). Each visit involves picking a single fruit and car-
 rying it away to a feeding roost where the fruit is ingested. Once a tree
 with mature fruits is located an individual bat may return to it
 repeatedly for over a week, but some time and energy are spent
 scouting for trees that will be in fruit in future days (Morrison 1978).
 For at least two weeks during the beginning of the dry season,
 when fruits are scarce and bat pollinated flowers are abundant, at least


1979