Terrestrial salamanders are useful indicator organisms. They maintain close contact with soil and are dependent upon the moisture of soil and leaf litter for gas exchange. Because of this, they are vulnerable to forest disturbance that results in loss of moisture. Their relatively long lives (some live over 20 years) and moist absorptive skins make them especially vulnerable to environmental toxins (Droege et al., 1997).
Few salamander studies have been conducted in the eastern United States (Petranka et al., 1993). The New York State Department of Environmental Conservation is currently conducting the first statewide survey of amphibian numbers (Roach 1998). This survey depends on volunteers, most of whom make observations only in spring and early summer. Proper survey requires a standardized system that is checked frequently throughout the seasons (Anonymous 1998). Seven New York amphibian species are currently either of special concern, threatened, or endangered. Until recently experts thought Long-tailed Salamanders (Eurycea longicauda) were plentiful in New York, but they may actually be our rarest salamander (Roach 1998).
Changes in salamander populations may reflect the health of the environment. Human alteration of the environment, including drainage of wetlands, stream pollution, agriculture, logging, and urbanization have been related to population declines (Petranka 1998). Clearcutting was associated with a loss of a local population of Plethodon jordani in southern Appalachia and may cause the annual loss of 14 million salamanders in US National Forests in western North Carolina (Petranka et al., 1993). Thousands are killed each spring as they cross highways during their migration from upland wintering areas to breeding ponds. They are especially vulnerable to human encroachment because their success depends upon both land and water habitats (Roach 1998). Dusky Salamander (Desmognathus fuscus) density is inversely proportional to urbanization gradients. The ground cover in areas of low urbanization give rise to stable stream banks and a cohesive substrate that is good for burrowing. High urbanization causes physical instability and leads to soil erosion and sediment in the water (Orser and Shure 1972). Some researchers suggest that environmental estrogens and anti-estrogens (including dioxins, pesticides, and PCBs) may interfere with amphibian reproduction by binding to estrogen receptors. As a result, fewer offspring are produced (Stone 1994). Acid precipitation and high levels of UV-B radiation have also been associated with declines in populations (Petranka 1998).
Alternatively, changes in amphibian numbers may merely reflect natural processes. Undisturbed local populations have almost disappeared in the past, but rebounded to previous highs within a decade. Long-term data are needed to put changes in amphibian populations in perspective (Pechmann and Wilbur 1994). Our survey is an important part of the gathering of knowledge, but coordination of our data with nationwide and worldwide studies is necessary to understand the over-all trend in salamander numbers.
We have established survey transects at two monitoring sites in northern Chautauqua County, New York following the protocol described in the North American Amphibian Monitoring Program (USGS Patuxent Wildlife Research Center, Laurel, MD).
Exterior grade plywood boards (12"x12"x1/2") serve as artificial cover objects. Pairs of boards (0.5 m apart) were spaced six meters apart along straight transects. The first monitoring site consists of one transect of 24 pairs of boards. The second site consists of two transects, the first with 10 pairs of boards; the second with 14 pairs.
Boards were numbered using a waterproof wide-nibbed pen. The area for each board was prepared by pushing aside the leaf litter and leveling the soil so the board would set on flat ground. We then covered the boards with leaf litter and left the transects undisturbed for about a month.
From May to December we checked the transects on a rotating weekly schedule. We uncovered one board at a time and captured all salamanders associated with it. One-pint plastic freezer bags marked with 0.5 cm rulings were used to measure the snout to vent length and the vent to tail tip length. We recorded the species and the lengths (to the nearest mm) of each salamander. We set the board back in position, allowed the salamanders to crawl under on their own, and re-covered the board with leaves.
Species of salamanders observed were Mountain Dusky (Desmognathus ochrophaeus), MD; Redbacked (Plethodon cinereus), RB; Slimy (Plethodon glutinosus), SL; Four-toed (Hemidactylium scutatum), 4T; Spotted (Ambystoma maculatum), SP.
Site 1. Total observed 407 MD 376 (92%) RB 30 (7%) SL 1 (<1%)
Preliminary work incompletely assessed numbers and viability of populations of other species. Scientists possess minimal data regarding the status of past and present terrestrial salamander populations. Because salamanders naturally have long lives, few offspring, and a vital role in the food web, changes in their numbers will affect the health of entire ecosystems. We need long-term data sets to alert us to potential problems and allow us to correct anthropogenic forces of change before irreversible damage has been done. It is easier and less expensive to correct a problem while it is still small than to wait until it is beyond repair (Droege et al., 1997). Alternatively, we need to know what is normal before taking funds away from other at risk species. If fluctuations really are normal, reporting declines as a crisis will damage credibility (Pechmann and Wilbur 1994).
LITERATURE CITED
Droege, S., L. Monti, and D. Lantz. 1997. The terrestrial salamander monitoring program. NAAMP document. http://www.im.nbs.gov/sally/.
Orser, P. N. and D. J. Shure. 1972. Effects of urbanization on the salamander Desmognathus fuscus fuscus. Ecology 53:1148-1154.
Pechmann, J. H. K. and H. M. Wilbur. 1994. Putting declining amphibian populations in perspective: natural fluctuations and human impacts. Herpetologica 50:65-84
Petranka, J. W. 1998. Salamanders of the United States and Canada. Washington: Smithsonian Institutional Press.
Petranka, J. W., M. E. Eldridge, and K. E. Haley. 1993. Effects of timber harvesting on southern Appalachian salamanders. Conservation Biology 7:363-370.
Roach, K. 1998. Leapin' lizards. New York State Conservationist 52:22-23.
Stone, R. 1994. Environmental estrogens stir debate. Science 265:308-310.
Site 2 #1. Total observed 34 RB 34 (100%)
Site 2 #2. Total observed 71 RB 51 (73%) MD 17 (24%) 4T 1(<2%) SP 1 escape 1
Anonymous. 1998. Late summer and early fall herping. Herp Atlas Newsletter Fall.