DODD: ECOLOGY OF SANDHILLS POPULATION OF GASTROPHRYNE CAROLINENSIS 15


soil layers beneath the soil surface (LaClaire and Franz 1990). The pond
continuously held water for two years prior to the initiation of my study, but its soil
profile suggests that periodic droughts are common (LaClaire and Smith unpubl.).
 The pond area was enclosed by a 230-m drift fence made of galvanized metal
flashing (36 cm above ground, 10-15 cm below the surface). No vegetation
overhung the fence, and the fence and pond area were exposed to direct sunlight.
Vegetation was kept cut and away from the fence exposing bare white sand for
about 40 cm from the base of the fence in either direction. The distance from the
drift fence to the nearest forest cover is generally 20 m, but extends to about 50-60
m behind the Panicum meadow. Within the enclosure, herbaceous hydrophytic
vegetation dominated the basin although a few shrubs, including buttonbush
(Cephalanthus occidentalis), myrtle holly (Ilex myrtifolia), and wax myrtle
(Myrica cerifera), were present. Several sapling longleaf and slash pines (P.
elliottii) grew within the enclosure. Maidencane and carpetgrass (Axonopus
furcatus) comprised 76 percent of the ground cover on vegetation transects
(LaClaire and Smith unpubl.).
 Pitfalls (19-1 black plastic buckets) were placed on opposite sides of the fence
at 10-m intervals following the procedures outlined by Gibbons and Semlitsch
(1982). In order to minimize the effects of direct sun, the buckets were partially
shaded with pegboard slanted over the openings in such a manner that there was
plenty of room for transit beneath the boards. Each board was laid flat across the
bucket opening on days when the pitfalls were not to be checked in order to prevent
desiccation of captured animals. Eastern narrow-mouthed toads were captured
even when the boards covered the bucket openings because the seals were not
complete.
 The pitfalls were checked 5 days per week between 0700 h and 0900 h,
depending on season, from October 1985 through September 1990 (1,273 days;
83,950 bucket nights). A year was defined as extending from October of one year
through September of the following year (e.g. "1986" covers October 1985 through
September 1986) for purposes of analysis. This yearly partition corresponds better
than the calendar year with amphibian activity patterns in north-central Florida.
 Frogs were measured in the field with a clear plastic ruler (snout-urostyle
length [SUL], defined as the tip of snout to the posterior portion of the urostyle)
and weighed to the nearest 0.1 g using a Pesola hand-held spring scale. Males
have a clearly visible black chin that is present in varying levels of intensity year-
round (Anderson 1954). In females the chin is mottled, light, and the same color
as the belly (Wright 1932). Females also occasionally contained eggs visible
through the ventral body wall. The sex was classified as "unknown" if there was
any question about the sex of the animal. Animals smaller than 21 mm SUL
generally were considered juveniles (Wright 1932; Anderson, 1954), although the
sex of some individuals was difficult to determine at 22-24 mm SUL (also see
Hecht and Matalas 1946). Anderson (1954) noted that G. carolinensis show adult
secondary sex characteristics across a range of sizes and that determining gonadal