Breeding Biology of the Gopher Frog, Rana capito, in Western Florida

Abstract

-The breeding biology of Rana capito was studied for one breeding season at a 1.2 ha pond in Okaloosa County, Florida. Frog movement was monitored with a drift fence and pitfall traps and egg deposition site selection was examined using wading surveys. A total of 301 unmarked adult frogs was captured, nearly half in February. Movement of immigrating frogs was positively correlated with rainfall. Frogs that entered and exited the pond only once, exited within an average of 38.5 m from the point of entry. Males spent more time in the basin than females and multiple-recaptured males stayed in the basin longer than single-recaptured males. Overall, the sex ratio did not differ from parity; however, nightly operational sex ratios were overwhelmingly male-biased. The eight-month breeding season (October through May) encompassed three major breeding events (one each in October, February, and April). A total of 146 complete egg masses was found, 67 of which contained an average of 2210 eggs. Frogs oviposited non-randomly, preferring rigid, vertical stems upon which to lay eggs. Each female deposited one egg mass. The gopher frog, Rana capito, is considered rare throughout its range (Martof, et al. 1980; Means, 1986; Dundee and Rossman, 1989; Godley, 1992), with habitat loss regarded as the greatest threat to its existence (Bailey, 1991). The terrestrial stage of the life cycle is threatened by habitat degradation or loss resulting from fire suppression, or habitat loss as a consequence of conversion for agriculture, plantation forestry, and real estate development. The larval stage is threatened by breeding site degradation due to drainage, siltation from road run-off, stocking of predatory fishes, and off-road vehicle use. Although various facets of its ecology have been investigated (Volpe, 1958; Franz, 1986; Bailey, 1990; Semlitsch et al., 1995), the natural history of R. capito remains poorly known. The only quantitative ecological study of R. capito was by Bailey (1990), who examined population size and structure, and environmental factors influencing movement of R. capito at a breeding site in Alabama. A better understanding of the breeding biology of R. capito is needed to address its conservation needs. My study was designed to gather data on (1) R. capito breeding migrations and breeding population size and structure, (2) the number of egg masses deposited per female, and (3) female oviposition site selection. MATERIALS AND METHODS Rana capito breeding biology was examined at Holley Pond, an isolated 1.2 ha depression marsh (Florida Natural Areas Inventory, 1990) on Eglin Air Force Base, Okaloosa County, Florida. Holley Pond is dominated by herbaceous vegetation, principally maidencane (Panicum hemitomon), spikerushes (Eleocharis spp.), hatpins (Eriocaulon compressum), bog-moss (Mayaca fluviatilis), floating hearts (Nymphoides aquatica), centella (Centella erecta), yellow-eyed grass (Xyris sp.), and panic grass (Panicum sp.). Holley Pond typically dries annually, and is comprised of three sub-basins that are connected at high water. Holley Pond occurs within an extensive, fire-suppressed longleaf pine (Pinus palustris)turkey oak (Quercus laevis) sandhill, and is immediately bordered by a narrow band of longleaf pine-live oak (Quercus virginiana) flatwoods. Frog movement into and out of Holley Pond was studied from 20 October 1994 to 19 May 1995 using a drift fence and pitfall traps. The drift fence was constructed from 30.5 m long x 0.9 m high rolls of black polypropylene silt-fencing, the bottom 15 cm of which was buried in the soil to prevent animals from burrowing beneath the fence. The ends of adjoining rolls were overlapped and secured with staples. Wooden stakes were used to support the fence. The fence, which completely encircled the pond, was 483 m long and an average of 15 m (range = 626 m) from the pond edge. Forty-seven pairs of 19 1 plastic buckets were sunk flush against both sides of the fence at approximately 10 m intervals. Each bucket was filled with water to a depth of approximately 2.5 cm and furnished with a sponge to provide cover for trapped animals and moisture if the water evaporated. With few exceptions, traps were checked daily in the morning and occasionally at night during peaks of frog migration. Buckets were covered on days when pitfalls were not checked. Frogs were measured with a plastic rule to the nearest mm (SVL) while flattened on their back, weighed to the nearest 0.5 gram with Pesola 217 This content downloaded from 157.55.39.106 on Mon, 25 Apr 2016 06:05:10 UTC All use subject to http://about.jstor.org/terms