BONACCORSO: A PANAMANIAN BAT COMMUNITY


However, in the next sampling period 50% of the females captured
were nulliparous, indicating that young of the year were entering the
flying population (top graph in Fig. 15). In the July-September sample,
65% of the females were nulliparous. The proportion of nulliparous
females then declined to 47% by the next sampling period. Associated
with the fact that only 16% of the females were nulliparous in March,
this pattern suggests a high mortality for females in the latter half of
their first year. Such a pattern has been found in temperate Myotis
(Humphrey and Cope 1976).

 DISCUSSION

DIVERSITY AND PHENOLOGY
 Maximal diversity in the bat community of BCI occurs from March
through July (Bonaccorso and Humphrey, in prep.), the principal
growing season. During this time rains are frequent yet light and
many plants and insects, having passed through reproductive inactiv-
ity in the dry season, undergo rapid growth and reproduction.
Deciduous trees produce new leaves, and mature fruits increase both
in diversity and biomass. Most of the large orders of insects, including
the Coleoptera, Lepidoptera, and Hymenoptera, explosively increase
in numbers and biomass. In general most of the food resources eaten
by bats, with the exception of nectar and pollen, are abundant during
the March-July period, and many species of bats that move out of the
forest habitat in the late wet season return by March.
 Minimal diversity within the bat community occurs in the late wet
 season. Fruit is scarce both in kinds of mature fruits and biomass, and
 fruit bat species diversity is lowest during this period. The species
 diversity of insectivorous bats also reaches a minimum during the late
 wet season. Though the actual numbers and biomass of insects are
 slightly lower in the dry season, the availability of insects as food for
 bats is probably lowest in the late wet season, when frequent rains cur-
 tail insect and bat activity.
 Communities formed by tropical bats are by far the most complex
 assemblages of sympatric mammalian species occurring anywhere in
 the world. Much simpler communities of bats are found in temperate
 latitudes. For example, Panama supports 104 known species of bats
 (Handley 1966), whereas similarly sized South Carolina contains only
 14 species, and all of the United States and Canada contain only 39
 species (Hall and Kelson 1959). Furthermore, 30 to 50 species of bats
 are commonly found coexisting within an area of a few square miles in
 Neotropical forests. Why are there so many more species of bats in
 tropical regions than are found in temperate regions of similar size?


1979