BULLETIN FLORIDA STATE MUSEUM


three canopy frugivores switch partly to pollen and nectar diets. In
drier forest habitats where suitable flowers are available over a longer
dry season, stenodermine bats feed on nectar and pollen through much
of the dry season (Heithaus et al. 1974).
 Adult females of all species in this guild have two litters per year.
 Birth pulses are synchronized within populations and coincide with
 the two predictable seasonal peaks in fruit abundance. Late term
 pregnancy, lactation, and learning processes associated with foraging
 by young bats, the events of highest energetic cost in the life cycle of
 mammals (Miguela 1969; Studier et al. 1973), occur at times of food
 abundance.

 GROUNDSTORY FRUGIVORES
 Groundstory frugivores specialize in eating fruits that grow on
 shrubs, most of which are less than 3 m high. These bats also feed on
 some canopy fruits, and in the dry forest areas of Belize (Bonaccorso,
 unpubl. data) and Costa Rica (Heithaus et al. 1974) guild members also
 feed on nectar and pollen in the long dry season.
 Two species in the subfamily Carollinae, Carollia castanea and C.
 perspicillata, form the groundstory frugivore guild on BCI. In closed
 canopy forest habitat throughout the Neotropical region, this guild
 contains fewer species than the canopy frugivore guild. In South
 America the other genus in the subfamily Carollinae, Rhinophylla, ap-
 pears to fit the groundstory guild (Handley 1967). Some species of the
 genus Sturnira (Stenoderminae) also may belong in this guild.
 Far fewer shrub species than tree species produce bat-dispersed
 fruits in tropical forests of Central America (12 versus 27 known
 species on BCI; also see Heithaus et al. 1974). Also, shrubs produce a
 much smaller range of fruit sizes than trees. On BCI shrub fruits
 preferred by bats range from about 0.2 to 2.0 g, a 10-fold range;
 whereas tree fruits range from about 2.0 to 30 g, a 15-fold range.
 Finally most shrub fruits are soft berries or catkins, but tree fruits ad-
 ditionally may be drupes, monkeypods, and other forms. Because of
 the greater variation in kinds, sizes, and shapes of canopy fruits there
 are many more ways to specialize on canopy fruits than on ground-
 story fruits, hence the larger numbers of species in the canopy
 frugivore guild.
 Groundstory frugivores have small home ranges in comparison to
large bats that specialize on canopy fruits. This probably occurs
because shrub food species are abundant as individuals and more
uniform in distribution than tree species. Groundstory frugivores
usually must visit a large number of shrubs each night to find suffi-
cient food. Each shrub has only a few small mature fruits available per


Vol. 24, No. 4