BONACCORSO: A PANAMANIAN BAT COMMUNITY


GROUNDSTORY FRUGIVORE GUILD
 BODY SIZE.-TwO species, Carollia castanea and C. perspicillata, in
the subfamily Carollinae of the Phyllostomatidae constitute the
groundstory frugivore guild on BCI. These have mean body weights of
12.4 and 17.9 g, thus differing in body weight by a factor of 1.44.
 A few Carollia subrufa were captured and banded by R. K. LaVal in
1972 on BCI (pers. comm.). In 1973 and 1974 I recaptured some of
LaVal's banded C. castanea and C. perspicillata, but I have not en-
countered any of the C. subrufa he marked. It is difficult to distinguish
C. perspicillata and C. subrufa by field characters, and it is possible
that I lumped a few individuals of C. subrufa with C. perspicillata
because I was not aware that C. subrufa was present on BCI. I believe
C. subrufa is very rare on BCI, and that lumping a few of them with C.
perspicillata would influence my data negligibly.
 FOOD SELECTION.-C. castanea and C. perspicillata are food
generalists eating a fairly even distribution of a large number of kinds
of fruits and have large niche breadth values (Tables 8 and 9). Though
no one food species dominates their diet in any one season, 11 species
of the woody shrub genus Piper (Piperaceae) constitute the bulk of the
diet of C. castanea and nearly one-third of the diet of C. perspicillata. I
identified 10 species of pipers in C. castanea fecal samples and 9
species from those of C. perspicillata. At least one species of piper has
mature fruits in any month on BCI (see Fig. 2). C. castanea and C.
perspicillata eat pipers all year long, but pipers were less important in
the diet of C. perspicillata from mid-September through mid-
November. C. perspicillata appears to feed almost exclusively on sub-
canopy and canopy fruits in the late wet season; particularly impor-
tant is Quararibea asterolepis. Other fruiting trees are important food
species along with pipers at other seasons. Though fruiting shrubs
dominate the diet of C. castanea, fruiting trees are somewhat more im-
portant than shrubs for C. perspicillata.
 In addition to fecal samples from captured animals, food habits
 data for C. perspicillata were obtained by monitoring droppings below
 two day roosts of this species. Both roosts were in hollow Anacardium
 excelsum trees. With the exception of fruit from A. excelsum, all com-
 mon food items identified from the day roost droppings appeared as
 important food items in fecal samples from captured bats during the
 same bimonthly periods (Table 10).
 Why did the fruit of A. excelsum never show in the fecal material
 from captured bats? Probably because Anacardium is the only tree
 species that commonly serves as both day roost and food source for C.
 perspicillata. These bats need only fly to the canopy of the roost tree,
 pick a fruit, and carry it inside the roost to eat it. The bats would


1979