DODD: ECOLOGY OF SANDHILLS POPULATION OF GASTROPHRYNE CAROLINENSIS 13


Semlitsch and Wilbur 1989). Drought also has been suggested as a contributing
factor in the apparent worldwide decline in amphibians, particularly anurans.
 Temporary ponds are dispersed throughout Florida's xeric uplands. These
ponds form in shallow clay-lined basins and typically fill during winter, spring, or
summer rains (LaClaire and Franz 1990). Summer thunderstorms are frequent but
scattered, and the often torrential rains help to maintain hydroperiod (i.e. the
amount of time standing water is in a wetland). As summer progresses, sandhill
ponds usually dry and remain without water through the autumn, unless rain from
a tropical depression or hurricane refills them. The wet-dry cycles are not regular,
however, and long periods with or without water are common.
 Many ponds in sandhill habitats lack fishes because they are not connected
with other wetlands. In addition, an unpredictable and locally variable
hydroperiod results in variability in invertebrate populations, such that predacious
species may or may not colonize particular ponds. The composition and
population sizes of invertebrate species are not consistent within a geographic
region because of variation in local wetland hydroperiod coupled with variation in
predators' abilities to colonize spatially fragmented habitats. The absence of fishes
and the potential for reduced levels of invertebrate predation allow amphibians,
particularly those species that do not have well developed antipredator defenses
(Kats et al. 1988), to reproduce in temporary ponds (Pechmann et al. 1989;
Bristow 1991; Dodd 1993).
 The importance of temporary ponds to a wide variety of wildlife is only
beginning to be appreciated (Moler and Franz 1988; LaClaire and Franz 1990). In
Florida sandhill communities, several species (e.g. Notophthalmus perstriatus,
Rana capitol aesopus) are obligate temporary pond breeders. Many other
amphibians, however, also breed in temporary ponds. From March 1983 through
February 1985, 13 anuran species bred in 10 temporary, isolated, clearwater,
sandhill ponds averaging 0.1-0.3 ha on the Katharine Ordway Preserve/Swisher
Memorial Sanctuary in Putnam Co., Florida (Moler and Franz 1988). Of 22
anuran species breeding in small isolated wetlands on the southeastern Coastal
Plain, 10 use temporary ponds as their principal or exclusive breeding habitat
(Moler and Franz 1988).
 In 1985, I began a 5-year study of a temporary wetland in the "high pine"
uplands of north-central Florida. The objectives of the project were to measure the
species richness, diversity, and dominance of the community (Dodd 1992) and to
gather basic information on the population biology of species that use the pond and
adjacent uplands. However, a prolonged drought during the study provided the
opportunity to examine the effects of drought on the amphibian community.
 In this paper, I report the results from data gathered on the eastern narrow-
mouthed toad, Gastrophryne carolinensis, the most abundant amphibian that
visited the pond. This toad is found from the Delmarva Peninsula south
throughout Florida and west to Missouri and Texas (Conant and Collins 1991).
The species is largely subterranean and secretive in habits, and its diet consists