Inventory and monitoring for amphibians of the Okefenokee National Wildlife Refuge.

INVESTIGATORS: Lora L. Smith; C. Kenneth Dodd, Jr.; Cynthia Loftin; Kristina Sorensen; Kevin G. Smith; and Jamie Barichivich.

PROJECT DESCRIPTION:

In response to concerns about amphibian population declines, the Department of Interior (DOI) received funding from Congress to institute long-term surveys of the status and trends of amphibians on DOI lands.  Long-term intensive monitoring will be conducted at selected index sites in the southeastern United States, including the Okefenokee National Wildlife Refuge in Georgia.  The inventory and monitoring plan for the Okefenokee NWR will include: 1) surveys of historic localities of rare or unusual species and an attempt to assess the current status of these species; 2) extensive sampling to determine species presence and distribution on the Refuge; and 3) intensive sampling at permanent monitoring sites within the Refuge.  In addition, researchers with the Maine Cooperative Fish and Wildlife Research Unit will develop spatial models that relate species-habitat associations and which can be used to predict suitable amphibian habitat.

The following narrative includes background information about the swamp and a description of the field sampling protocol for the first phase of the project at Okefenokee NWR.  The sampling protocol will entail quadrat-based species richness sampling that presumably can be developed into a suitable monitoring program (Nichols and Conroy, 1996; Nichols, et al., 1998).

The Okefenokee Swamp is a 200,000 ha freshwater wetland in southeast Georgia and northeast Florida.  The Refuge encompasses approximately 158,000 ha of the swamp.  Habitat types within the Refuge include forested wetlands (57%) containing pond cypress (Taxodium ascendens), titi (Cyrilla racemiflora), loblolly bay (Gordonia lasianthus), blackgum tupelo (Nyssa sylvatica), hurrahbush (Lyonia lucida), and dahoon (Ilex cassine) (Loftin, 1998).  Most large cypress trees were logged out of the swamp in the early 1900s.  Dense, impenetrable shrub thickets of titi, hurrahbush and fetterbush (Leucothoe racemosa) cover 29% of the swamp.  Wet prairies with yellow-eyed grass, Walter's sedge (Carex walteri), spatterdock (Nuphar luteum), fragrant water lily (Nymphaea odorata), and golden club (Orontium aquaticum) cover 8% of the swamp. Narrow boat trails and lakes transect the wetland habitats of the swamp. The remaining 5% of the Refuge consists of forested uplands with slash pine (Pinus elliottii), longleaf pine (Pinus palustris), saw palmetto (Serenoa repens) and gallberry (Ilex glabra). Upland forests on the east side of the Refuge consist of mesic pine flatwoods and scrubby flatwoods. Those on the southern and western periphery of the Refuge are mesic pine flatwoods.  The numerous islands within the swamp also contain pine flatwoods. A number of small ponds and cypress strands occur in the pine flatwoods, particularly in the western part of the Refuge.

The earliest investigations of the amphibians of the Okefenokee Swamp were undertaken in the early 1900s by A.H. Wright and students from Cornell University. Wright (1932) wrote extensively of the biology of Okefenokee anurans. In the 1960s, C.H. Wharton and students from the University of Georgia made extensive collections of amphibians from the region.  In the late 1970s, researchers from the University of Georgia conducted vertebrate surveys in the swamp and surrounding uplands (Laerm et al., 1980).  More recent amphibian research includes surveys for rare pond breeding amphibians (Dodd and LaClaire, 1995; Jensen, 1995). A total of 21 frogs and 17 salamanders have been reported from the Swamp.

Human activity in the swamp has included logging, dredging, peat mining, and water impoundment (Suwannee River Sill). Fires (both natural and anthropogenic) have played a large role in shaping the character of the swamp.  Conservation issues of concern to the refuge include the effects of removal of the Suwannee River Sill, effects of environmental contaminants (particularly heavy metals), and impacts of adjacent land uses such as silviculture and a proposed titanium mine.

Surveys of Historic Localities: Where possible, historic localities of rare species (Table 2) will be visited to determine whether these species are still present, and emphasis will be placed on surveying additional sites likely to host rare amphibians, e.g., temporary ponds for striped newts (Notophthalmus perstriatus), gopher frogs (Rana capito), and flatwoods salamanders (Ambystoma cingulatum). Surveys will be concentrated in the breeding season and will focus on call surveys for frogs and dip-netting for larvae and adult salamanders. Habitats that appear suitable for species at the periphery of their range such as the many-lined salamander (Stereochilus marginatus) and carpenter frog (Rana virgatipes) also will be surveyed. A Global Positioning System (GPS) will be used to determine the precise localities of rare amphibians and their breeding sites.

Extensive Surveys: These surveys will be used to document amphibian occurrences at as many sites on the Refuge as possible.  Sites will be chosen based on vegetative community/habitat type, hydrology, and region and the number of sites sampled will be based on the amount of habitat available. A subset of the extensive sites will be sampled repeatedly to evaluate within and between year trends in species richness.

Extensive surveys will include the use of area and time-constrained searches for amphibians (Scott, 1994). In upland habitats and wetlands with little or no standing water, leaf litter, logs, and other debris will be turned in search of ground-dwelling amphibians.  The species, numbers of individuals and life stage of each species observed will be recorded, as well as the number of person-hours invested at each site. Characteristics of the environment/habitat, sampling conditions (weather, air temperature, substrate temperature, water temperature, relative humidity), and the number of animals observed or captured, by species, will be recorded. Logs or litter that are displaced will be returned to their original position to minimize disturbance to the substrate.

In aquatic habitats dredges, dip nets, or seine nets will be used to survey for aquatic adults and larvae. The number of net/dredge sweeps per site and the length of time invested will be recorded. In addition to time-constrained surveys, anuran vocal activities will be monitored monthly at selected wetlands in the Refuge. 

Intensive Surveys: A number of intensive sampling sites will be established within the different vegetative communities within the Refuge. Surveys at terrestrial areas within intensive sites will include time-constrained and/or area-constrained searches. Passive sampling methods such as cover boards and PVC pipes also will be used at intensive sites.  Cover boards will be placed in terrestrial areas and PVC pipes will be placed in forested wetlands, shrub wetlands, prairies, and around ponds and lakes.

Aquatic habitats within permanent sites will be sampled using different types of nets as deemed appropriate for the amount of water present (e.g., hand-held dip nets; dredges, or seine nets).  More intensive sampling measures such as minnow traps, crayfish traps, debris bags (Pauley and Little, 1998), and drift fences (Dodd and Scott, 1994; Enge, 1997) also may be used.  Computer data loggers to record continuous temperature, relative humidity, and barometric pressure will be placed at each intensive site.  Characteristics of the environment/habitat, sampling conditions, and the number of animals observed or captured, and life stage, will be recorded by species.

General Surveys: All amphibians incidentally encountered while performing field tasks at Okefenokee will be recorded.  In addition, periodic road surveys will be conducted monthly on paved roads through the Refuge (Schaffer and Juterbock, 1994). Surveys will take place after dark, particularly during or after rain.  All live and dead amphibians will be counted and the total mileage driven will be recorded. Locations of rare or unusual species will be determined with a GPS.

References:

Conant, R. and J.T. Collins. 1998. A Field Guide to Reptiles and Amphibians. Houghton Mifflin Company, Boston.

Dodd, C.K., Jr., and D.E. Scott. 1994. Drift fences encircling breeding sites. pp. 125-130. In Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. Heyer, W.R., M.A. Donnelly, R.W. McDiarmid, L.C. Hayek, and M.S. Foster (eds.). Smithsonian Institution Press, Washington, D.C.

Dodd, C.K., Jr., and L.V. LaClaire. 1995. Biogeography and status of the striped newt (Notophthalmus perstriatus) in Georgia, USA. Herpetological Natural History 3(1): 37-46.

Enge, K.M. 1997. A standard protocol for drift fence surveys. Technical Report No. 14. Florida Game and Freshwater Fish Commission. Tallahassee, FL.

Jensen, J.B. 1995 Survey of potential habitat on Okefenokee National Wildlife Refuge for Ambystoma cingulatum, Rana capito, and Notophthalmus perstriatus. Report to the U.S. Fish and Wildlife Service. order No. 4310-5-0092.

Laerm, J., B.J. Freeman, L.J. Vitt, J.M. Meyers, and L. Logan. 1980. Vertebrates of the Okefenokee Swamp. Brimleyana 4:47-73.

Loftin, C.S. 1998. Assessing patterns and processes of landscape change in Okefenokee Swamp, Georgia. Ph. D. Dissertation, University of Florida, Gainesville, FL.

Pauley, T.K., and M. Little. 1998. A new technique to monitor larval and juvenile salamanders in stream habitats. Banisteria 12:32-36.

Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington, D.C.

Schaffer, H.B., and J.E. Juterbock. 1994. Night driving. pp. 163-166. In Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. Heyer, W.R., M.A. Donnelly, R.W. McDiarmid, L.C. Hayek, and M.S. Foster (eds.). Smithsonian Institution Press, Washington, D.C.

Scott, N.J., Jr. 1994. Complete species inventories. pp. 78-84. In Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. Heyer, W.R., M.A. Donnelly, R.W. McDiarmid, L.C. Hayek, and M.S. Foster (eds.). Smithsonian Institution Press, Washington, D.C.

Wright, A.H. 1932. Life-histories of the frogs of Okefinokee Swamp, Georgia. The Cayuga Press, Ithaca, NY.