Sampling Methods

Amphibian Sampling

       Most species of amphibians of the southeastern U. S. coastal plain region breed in wetlands (e.g., ponds, streams, lakes), we focused our 2005 sampling in aquatic habitats to inventory amphibian species richness, identify appropriate sites for long-term monitoring, and determine the distribution of breeding sites.  Focusing long-term amphibian monitoring at wetlands will allow us to maximize species detection probabilities and identify important covariates (e.g., pH, fish predators) influencing detection and proportion of area occupied.  We used a variety of methods to sample amphibians at each refuge (Table 1). Terrestrial sampling techniques included field searches (i.e., visual encounter surveys) for animals in the open and under cover objects (e.g., logs, rocks) and road cruises (i.e., making opportunistic observations while driving roads, typically at night). Aquatic sampling consisted of the use of dip nets (Memphis Net and Twine Co., HDD-2 with 3/16" sq. Delta mesh), crayfish traps (Johnson and Barichivich, 2004), aural surveys (incidental observations and using automated frog-call data loggers, Barichivich, 2003), and visual encounter observations.

Water Quality Data

       We collected standard abiotic field parameters likely to influence amphibian species distribution at most of the wetlands sampled.  Using a Hydrolab® Quanta® water-quality meter we measured water temperature (ºC), conductivity (mS/cm), pH, dissolved oxygen (mg/l), and % dissolved oxygen.  More detailed water quality parameters were measured at selected wetlands in St Marks NWR by USGS Water Resources Discipline (WRD) personnel in Aug 2005.  Field parameters, major ions, nutrients, trace metals, and suspended/particulate organic carbon from these sites were analyzed by WRD.

Voucher Specimens and Disease Monitoring

       We collected limited numbers of animals for voucher specimens, to confirm species identification, and for disease screening. Many voucher specimens were collected as dead-on-road (DOR) individuals, and turtle shells were collected when found.  Because of difficulty in positively identifying amphibian eggs and small larvae, live specimens were occasionally collected and reared at the USGS lab in Gainesville, FL, to confirm species identifications. These specimens were preserved as vouchers once identifications were confirmed.  All voucher specimens were (or will be) deposited in the herpetology collection of the Florida Museum of Natural History at the University of Florida, Gainesville.

       We collected amphibian larvae at several wetlands at St Marks, Harris Neck, and Savannah NWRs for disease screening by the National Wildlife Health Center. We also collected amphibian larvae from several sites in Florida where die-off events were observed, including the Withlacoochee State Forest and the Katharine Ordway Preserve – Swisher Memorial Sanctuary.

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