BONACCORSO: A PANAMANIAN BAT COMMUNITY


season. Howell and Burch (1974) reported that it ate insects. Nothing
beyond Jeanne's (1970) observations of P. stenops eating social wasp
larvae and my two observations of fruit eating is known about the diet
of this bat.
 Phyllostomus discolor is neither an extreme specialist nor a
generalist in food species (niche breadth = 1.65). Several types of
flowers are visited for pollen and nectar in the dry season and, in addi-
tion to insects, several types of fruit are eaten in the wet season. The
available data are too limited to consider niche breadth values for P.
stenops and G. soricina.
 VERTICAL STRATIFICATION.-All flowers and fruits eaten by P.
discolor and 83 percent of those eaten by G. soricina in this study grow
in the subcanopy and canopy of the forest. Both species were captured
most frequently in upper levels of the forest, 3 of 4 for Glossophaga
and 40 of 54 for Phyllostomus. For P. discolor preference for flying
above groundstory shrubs is highly significant (P < .01, Chi Square
Test).
 HABITAT SELECTION.--Phyllostomus discolor was common in the
mature forest and second growth but uncommon over creeks. Some of
the important tree species producing flowers and fruits eaten by
Phyllostomus are common only in second growth (e.g. Ochroma),
others are common only in mature forest (e.g. Pseudobombax), and
still others are common in both habitats (e.g. Cecropia).
 FEEDING BEHAVIOR.-During the dry season bats are frequently
 captured with pollen heavily dusted over the anterior body. It is likely
 that these animals visit numerous flowers in succession, consuming
 nectar and performing pollination services at each flower, and later
 while roosting ingest pollen by grooming it from the fur and skin.
 None of the bats in this guild were captured carrying fruit.
 Of the P. discolor captured in all-night samples, 69 percent were
 taken within two hours of sunset. Such a strong unimodal pattern of
 flight activity (Fig. 9) also is reported by LaVal (1970) and suggested
 by Heithaus et al. (1974) for this species in Costa Rica. My data are in-
 sufficient for discussing flight activity cycles of Glossophaga, but
 LaVal (1970) reported a strong activity peak at dusk and in the first
 hour of darkness, just before peak P. discolor activity.

 SANGUIVORE GUILD
 BODY SIZE.-Of the three extant vampire species, only Desmodus
 rotundus, the common vampire, inhabits BCI and surrounding areas.
 The mean prefeeding body weight of D. rotundus is 33.5 g.
 FOOD SELECTION.-Wild vampires feed only on the blood of
 homoiothermic vertebrates (McNab 1973). While vampire feeding