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Survey of Iron County Reptiles and Amphibians

Carol A. Strojny
Wisconsin Department of Natural Resources
PO Box 588
Mercer, WI 54547

University of Wisconsin - Stevens Point
Stevens Point, WI 54481

[ Abstract ]
Dreux Watermolen (1996) stated that according to the Natural Resource Council, worldwide amphibian population declines are resulting from a series of factors including widespread destruction of habitat, changing land uses, competition from other species, and natural causes such as drought. Reptile and amphibian groups, collectively referred to as herptiles, are receiving worldwide efforts to monitor trends and responses to habitat changes. Amphibians are especially vulnerable to habitat modifications because they rely on both aquatic and terrestrial habitats (Wyman 1990).

In Wisconsin, the Department of Natural Resources (WDNR) coordinates an annual frog and toad survey which was initiated in 1981 (Watermolen 1996). This survey does not cover salamanders, snakes, and turtles. The Wisconsin herpetological atlas, coordinated through the Milwaukee Public Museum, began in 1985 to cover the distribution of all herptiles by working with and collecting data from individuals, conservation groups, and the WDNR. Within the WDNR's Bureau of Endangered Resources (BER), the Natural Heritage Inventory Program (NHIP) also uses herptile data (Casper 1996). Their goal is to create and maintain an inventory of rare or declining Wisconsin animal and plant species, habitats, and communities (DNR files, unpubl. data).

My study was designed to provide additional information and documentation for the Wisconsin herpetological atlas and NHIP. Eight potential species for the county have been emphasized to expand the known herptile distribution in the state. Results were analyzed to suggest future monitoring and emphasis needs. This study benefits the DNR by contributing information regarding Iron County's natural history and biodiversity, which will impact future landscape management.

Funding for my internship was provided by the Wisconsin Department of Natural Resources through the University of Wisconsin - Stevens Point. I thank Bruce Bacon for assisting with the project design and supplies, Claire Gower for helping with data collection, Consolidated Paper Company and the Liddicoat family for providing access to their property, and Lyle Nauman for helpful comments and reviews of this paper.

Study Area
Iron County, 166,340 ha in size, is located in northern Wisconsin. Annual precipitation averages 88.9 cm; January temperatures averages -11.0 C and July averages 19.3 Celsius. Within a year, the temperature falls below -17.8 C for an average of 38 days, and is greater than 32.2 C for an average of 4 days (Garwood 1996). The major forest types were northern hardwoods and aspen forests, with swamp conifers prevalent on poorly drained soils throughout the county (Kotar et al. 1988). Timber harvest, recreational trails, and lake-shore development are disturbances which may negatively affect herptiles within the county.

The 5 study sites were chosen to represent different forest and soil types found in Iron County (Fig. 1). Each site had an ephemeral pond less than 0.04 ha, except for the Mercer School Forest location which had a permanent marsh approximately 0.8 ha in size.

Five herpetological sampling stations were established in early June to monitor reptiles and amphibians regularly throughout the summer. A data sheet was used to record observations and conditions at the site (Table 1). Water pH was initially measured and then discontinued. The available pH kit did not measure pH below 5.5. Since Kutka and Bachmann (1990) found no pattern of amphibian distribution by pH in northern Wisconsin ponds, I saw no further need to pursue pH measurements. Results from random sampling of wetlands and casual observations of turtle crossings or other herptiles were recorded in an Iron County herptile distribution booklet (Table 2). Each species had a corresponding map to mark locations, color coded by year.

Several techniques were applied to target all herptile species (Corn and Bury 1990). The methods used were selected to cover terrestrial and aquatic species as well as terrestrial and aquatic stages of the same species. Each site was checked at least once per week. Captured animals were identified and released. At the end of the internship, all traps were removed from the study sites except for the artificial cover objects. A species list was compiled for each study site using the collected data (Table 3). Information from the data sheets was summarized by site (Appendix A-E). Trapping techniques were compared by listing species found at each study site (Table 4). The design for this study was based on an "Amphibian and reptile field methods workshop" (pers. comm. G. Casper, Univ. of Wisc. - Milwaukee Field Stn. Cedar bog, 25 May 1996).

Artificial Cover Objects
Flat boards approximately 1m x 1m x 3 cm were layered with scrap wood on the underside to provide a desirable microhabitat for snakes, lizards, and salamanders (Fellers and Drost 1994). Two were placed at each site within visible distance of the wetland. Birch Hill and the Liddicoat site had adjacent grass areas which were included in the sample area by placing one of the cover objects there. The cover objects were placed on raspberries (Rubus sp.), the dominant terrestrial plant at the clear-cut site.

Funnel Traps
Funnel traps (minnow traps) targeted salamanders and frogs (adults, tadpoles, and larvae). They were nearly submerged allowing a 5-cm air space, adjusted as needed to changing water levels (Lannoo 1996). All sites had 1 trap except for Birch Hill which had 2.

Leaf Bags
Mesh bags (1-cm mesh, 35-cm length, 6-10 cm width) were filled with leaves and vegetation. One end was held open with a wire hoop providing a 12-cm diameter entrance and exit. These were submerged under water to provide a burrowing habitat for salamanders and newts. The leaf bags were examined by placing them in buckets with water and sifting through the material. This technique is relatively new and untested (Lannoo 1996). Each site had 3 leaf bags.

Drift Fence With Pitfalls
Approximately 3.6-m long x 30.4-cm high tin fences were erected with 3-lb coffee cans as pitfalls at each end. The fences were placed parallel to the wetland to intercept frogs and salamanders. Holes for drainage were punched in the bottoms to prevent flooding and drowning of captured animals.

Dip Netting
A minimum of 5 dips using a net with a 50-cm diameter and 1-cm mesh was done per site visit to sample presence of frogs, eggs, or salamander larvae. This is considered a course index of presence/absence due to biases with time of day, weather influences, and species activity (Lannoo 1996). Dip netting was used at both permanent and random sites.

Casual observations describing life stage, habitat, and location were done at each visit to the sites and randomly. Field personnel also contributed herptile sightings.

The audio technique recorded any frogs heard during visits. Evening visits were not done. The internship began after the first listening period as designated in the Wisconsin frog and toad survey (Mossman and Hine 1984). Two random county road survey routes were set up for future use. These routes differ from the Wisconsin frog and toad survey by not having pre-selected wetlands as stopping points. Stopping points are at every tenth of a mile along the 10 mile route. Timing of year and duration of listening periods follow the guidelines of the Wisconsin frog and toad survey (Mossman and Hine 1984).

Natural Cover Objects
This method involves sifting through organic matter and under logs, rocks, and brush looking for salamanders, snakes, and lizards. This summer, this technique was done once at each permanent site for a duration of 20 minutes.

Wood frogs and American toads were found at each study site. The most species found were at Birch Hill (10), followed by Underwood (7), Mercer School Forest (6), Clear-cut (6), and Liddicoats (4) (Table 3). No species were captured using the leaf bag technique. The funnel traps captured non-targets and herptile already recorded either by visual or audio techniques. The drift fences with pit-falls caught adult salamanders and some frogs, many toads, and rodents. There was an increase in species and number of individuals caught after replacing some coffee cans with 18.9-L (5-gallon) buckets. Dip netting resulted in mainly tadpole or salamander larvae absence/presence data. Artificial and natural cover structures were the only methods besides visual observation to locate snakes.

The study began the last week of May and ended the third week of August. Visits per site averaged 11 days and trap nights averaged 75. For potentially occurring species, documentation for the chorus frog (Pseudacris triseriata) and mudpuppy (Necturusmaculosus maculosus) were submitted to the WI Herpetological Atlas for Iron County. The required evidence was collected from DNR employees. The chorus frog was the only new species found by the survey methods. All others remain on the wanted list (Fig. 2).

Based on the paucity of data, a comparison of habitats is highly subjective. The internship began after the first salamander movements and frog calling periods. Starting the study earlier may have provided more data. "Ice out" is the time to establish drift fences and begin audio surveys (Watermolen 1996 ).

Larval and tadpole sampling is considered an integral part of any sampling program by being a quick and efficient sampling method (McDiarmid 1994). However, lacking the expertise on identification of larval and tadpole stages, sampling this stage did not provide specie names. All Wisconsin anurans call during certain breeding periods (Mossman and Hine 1984). I recommend audio sampling in place of tadpole sampling.

Dip netting, leaf bags, and funnel traps are not recommended techniques for future monitoring. The microhabitat provided by the leaf bags was naturally available at each site. Dip netting and funnel trapping did not capture herptiles which were not surveyed by the other techniques. Emphasizing drift fences with pit falls would provide more information. Pitfall variations are able to determine species richness, detect the presence of rare species, and yield data on relative abundance and habitat use (Corn 1994).

The artificial cover objects were not highly successful. The unusually wet season may have resulted in salamander populations utilizing the damp leaf litter instead of crawling under artificial or natural cover objects (Jaeger 1980). Cover objects may work better in dryer seasons. More cover objects in the Birch Hill area may provide for quicker location of sand loving potential species such as the eastern hognose snake (Heterodon platirhinos) and northern prairie skink (Eumeces septentrionalis septentrionalis). Time - constrained searches are best for presence/absence data and microhabitat information. Searching the microhabitats with the highest probability of containing the targeted species is a quick and inexpensive way to attain a species list (Corn and Bury 1990). This would be a good method to fill gaps in the herptile atlas.

An inventory, which collects a list of species, is very intensive and would work well to study the DNR's concerns for logging and road impacts on herptile microhabitat. Microhabitat is very important to the ecology of amphibians; Keen (1984) shows that salamander activity is suppressed under low moisture conditions, resulting in less foraging, courtship, and mating time. However, slash piles left over from cut areas are helpful in supporting herptiles. Sensitive species, such as the red-backed salamander, are also more likely to immigrate if the cut is adjacent to "older growth" (Pough et al. 1987) Perhaps this explains the herptile presence in the clear-cut study area located adjacent to Liddicoats mixed forest.

It is important to continue surveying Iron County's herptiles to show trends over time. To collect substantial data, a greater time investment is required along with a narrower scope. Continued efforts to collect casual observations from employees and the public will expand the knowledge of herptile distribution while increasing awareness of these low profile animals.

Casper, G. S. 1996. Geographic distributions of the amphibians and reptiles of Wisconsin. Milwaukee Public Mus., Inc. Milwaukee, Wis. 87 pp.

Corn P. S. 1994. Standard techniques for inventory and monitoring: straight-line drift fences and pitfall traps. Page 109 in W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. A. C. Hayek, and M. S. Foster, eds. Measuring and monitoring biological diversity: standard methods for amphibians. Smithsonian Inst. Press. Washington, D. C.

Corn, P. S. and R. B. Bury. 1990. Sampling methods for terrestrial amphibians and reptiles. USDA, For. Serv. Gen. Tech. Rep. PNW - GTR - 256. 34 pp.

Fellers, G. M. and C. A. Drost. 1994. Sampling with artificial cover. Pages 146-150 inW. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. A. C. Hayek, and M. S. Foster, eds. Measuring and monitoring biological diversity: standard methods for amphibians. Smithsonian Inst. Press. Washington, D. C.

Garwood, A. N., editor. 1996. Weather America. Toucan Valley Publ., Milpitas, Calif. 1412 pp.

Jaeger, R. G. 1980. Microhabitats of a terrestrial forest salamander. Copeia 1980:265-268 pp.

Keen, W. H. 1984. Influence of moisture on the activity of a plethodontid salamander. Copeia 1984:684-688 pp.

Kotar, J., J. A. Kovach, and C. T. Locey. 1988. Field guide to forest habitat types of northern Wisconsin. Dep. For., Univ. of Wis. - Madison, and Wis. Dep. Nat. Resour. 134 pp.

Kutka F. J. and M. D. Bachmann. 1990. Acid sensitivity and water chemistry correlates of amphibian breeding ponds in northern Wisconsin, USA. Hydrobiologia 208:153-160.

Lannoo, M. 1996. Aquatic amphibian surveys. Online. Internet. Available: 11 June 1996.

McDiarmid R. W. 1994. Amphibian diversity and natural history: an overview. Page 73 in W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. A. C. Hayek, and M. S. Foster, eds. Measuring and monitoring biological diversity: standard methods for amphibians. Smithsonian Inst. Press. Washington, D. C.

Mossman, M. and R. Hine. 1984. The Wisconsin frog and toad survey: establishing a long-term monitoring program. Wis. Dep. Nat. Resour., Bur. of End. Resour. 13 pp.

Pough, F. H., E. M. Smith, D. H. Rhodes, and A. Collazo. 1987. The abundance of salamanders in forest stands with different histories of disturbance. For. Ecol. and Manage. 20:1-9.

Watermolen, D. J. 1996. All about amphibians. Wis. Nat. Resour. 20:4-10.

Wyman, R. L. 1990. What's happening to the amphibians? Conserv. Biol. 4:350-353.


U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
Contact: Sam Droege, email:
Last Modified: June 2002