January 1, 1987 to December 31, 2011
These tables give a rough idea of the relative abundance of Vermont’s reptiles and amphibians. The comparisons are subject to bias by the audibility, visibility, notoriety, and ease of identification of species. For example, since salamanders don’t call and are usually under cover, they are reported less often than frogs. Consequently, the species are sorted by taxonomic group so that some of these biases are alleviated. However, some other biases remain. For instance, Eastern Ribbonsnakes when observed may be assumed to be Common Gartersnakes and hence they may be under-reported. Aquatic species of turtle that bask only infrequently are probably reported less often than terrestrial or basking species.
Still, these tables help the Scientific Advisory Group decide if the state rank and/or state status of a species needs to be reevaluated. Species are listed in descending order of the number of “sites” from which they have been reported. Errors in the number of known sites and towns for the more abundant species are almost certainly included and those numbers are changing monthly. There are a total of 255 “towns” (political units including towns, cities, gores, and unincorporated areas) in the state of Vermont.
State Ranks in the tables below are as of December 2013.
|Species||# of Towns||# of Sites||State Rank||State Status||Site Size||SGCN Status|
|Northern Map Turtle||19||39||S3||SC||4.2km|
|Eastern Musk Turtle||13||14||S2||SC||8.0km||Medium|
|Eastern Box Turtle||6||7||N/A||Hypothetical||2.6km|
|Species||# of Towns||# of Sites||State Rank||State Status||Site Size||SGCN Status||Last Observation|
|North American Racer||10||7||S1||T||9.6km||High||2014|
|Eastern Hog-nosed Snake||2||2||N/A||Hypothetical||3.2km|
The Ring-necked Snake’s state rank was changed from S3 to S4 in 2013 by the Scientific Advisory Group.
|Species||# of Towns||# of Sites||State Rank||State Status||Site Size||SGCN Status|
|Common Five-lined Skink||2||17||S1||E||0.5km||High|
Methods used for Relative Abundance Tables for Vermont Reptiles and Amphibians
These tables are intended to give the reader an idea of the relative abundance and distribution of Vermont herptiles based on the data in the Vermont Reptile and Amphibian Database. The more common the species, the less accurate the data presented. Exact locations of some reports are difficult to pin down and the large number of reports of more common species makes it certain that some mistakes are included, particularly in the number of sites per species for S4 and S5 species. Detailed location maps have only been generated for a handful of the rarest species. Still, the relative rankings within taxonomic groups should be accurate. Numbers of towns and sites for this set of tables were generated by volunteer Elizabeth Volpe and edited by Jim Andrews. Site sizes were generated by Erin Talmage and also edited by Jim Andrews.
Both the reptile and amphibian charts summarize data that were gathered by volunteers and professionals using a variety of methods. Historical records (before January 1, 1987) were not included, nor were records entered after December 31, 2011. All reports that had been assigned an unverified status in the Vermont Reptile and Amphibian Database were omitted and have not been included in these charts. For rare and often misidentified species, records without vouchers (photos, shed skins, specimens) that came from disjunct locations were not included. In addition, records that were assumed to be released pets were not included. However, for common species in appropriate habitat we did include records that were well described but not accompanied by a voucher photo or specimen. Salamanders identified as Jefferson X Blue-spotted Complex were omitted since they could not be placed in any one species or group.
The size of a “site” varies with the species. Since many herptiles have one or more central habitat features that are required for the persistence of a population (dens and hibernacula, breeding sites, foraging sites, drought refugia, ponds, streams) we estimated a maximum traveling distance based on the literature and unpublished local research. We then doubled this distance assuming that individual organisms might travel in opposite directions from any one feature. Two records further apart than this distance were counted as separate sites. For all amphibians and the most common (S5) small snakes, we defined a site as a location that is equal to or greater than one-half kilometer from the nearest reported location. If two or more records were gathered within a half-kilometer of each other, they were considered to be the same site. For all other species, we used a site-size we felt was appropriate for the species based on its natural history as observed in the field and reported in the literature (see details below). Over time, as additional data are gathered, these site sizes may need to be adjusted.
Determining site size for selected reptiles
North American Racer (Coluber constrictor) – We have found (Andrews unpublished research) that Eastern Racers in Vermont traveled almost 3 miles (4.8 km). Therefore, snakes sharing the same den could potentially be found 4.8 km in any direction or up to 6 miles apart (9.6 km). Hence records had to be more than 9.6 miles apart to be considered separate sites (site size = 9.6 km).
Timber Rattlesnake (Crotalus horridus) – Male Timber Rattlesnakes have a home range of 65 – 207 ha (Ernst and Ernst 2005). Unpublished local data suggest a probable maximum travel distance of less than 4 miles (6.4 km). Therefore we used a site size as an area 8 miles (12.8 km) in diameter with a known denning area as the center. Only reports from currently-vouchered sites were included.
Eastern Ratsnake (Pantherophis alleghaniensis) – As with all snakes there is a variety of home range size and average distances traveled. A study in Maryland found individual snakes traveling between 0 – 1.2 km with the diameter of an individual’s home range for males to be at least 600 m and for females to be 500 m (Ernst and Ernst 2005, Stickel et al. 1980). However, our own radio-tracking studies in Vermont showed that snakes traveled at least 1.75 miles (2.8 km) between denning and foraging areas. Additional reports strongly suggest that other ratsnakes using known dens were traveling slightly over two miles (3.2 km). If two reports were less than 6.4 km (4 miles) apart they were counted as one site.
Eastern Hog-nosed Snake (Heterodon platirhinos) – This species was only recently discovered in Vermont and has not yet been added to our resident breeding species list, but it may be in the future. According to Platt (1969) in Ernst and Ernst (2005) the longest distance moved by any of the snakes in their study was 1.6 km. So, we have used a minimum distance of 3.2 km (2 miles).
Common Watersnake (Nerodia sipedon) – A distinct water body, such as Bristol Pond, was counted as one site. Fitch (1999) found that the greatest straight-line distance a watersnake traveled was between 1.15 and 1.73 km and movements over 1 km were made by both sexes in almost all compass directions. Therefore, in situations where they were found along a waterbody (river or lake shore), distances greater than 2 km were counted as separate sites.
Eastern Ribbonsnake (Thamnophis saurita) – We could find no reports in the literature of maximum travel distances from foraging habitat to denning sites for this species. Maximum travel distances to den sites reported for the closely related Common Gartersnake (Thamnophis sirtalis) ranged widely from 1.3 km in Kansas (Fitch 1999) to 17.7 km in Manitoba (Gregory and Stewart 1975). Based on the clusters of records from sites in Vermont and our knowledge of wintering areas, the most conservative distance (1.3 km) seemed to fit our known distributions. Consequently we used a site size of 2.6 km (1.6 miles). In locations where we are aware of suitable denning habitat closer to the sighting than the site size would allow, we broke clusters of sightings into separate sites.
Spiny Softshell (Apalone spinifera) – Based on the literature and studies within Lake Champlain, we know that softshells frequently traveled from the Causeway north up the Pike River to Route 133, a distance of as long as 15.5 miles (25 km) so we assume that they can travel about 15.5 (25 km) miles south, thereby giving this species a large site area (31 miles (50 km)), with one site covering a number of towns.
Snapping Turtle (Chelydra serpentina) – One study found that the average distance moved (N=107) was 1.1 km. (Ernst et al. 1994). Consequently, we used a maximum travel distance of 1.5 km and all turtles found within a small water body or along a river less than or equal to 3.0 km were considered 1 site.
Painted Turtle (Chrysemys picta) – If a small water body was less than or equal to 2 km long it was considered one site. The literature suggests that their home range is relatively small (Howe 2003) but an individual can travel a considerable distance for nesting or other purposes.
Spotted Turtle (Clemmys guttata) – During a spring movement study in South Carolina researchers (Lovich 1990a, Ernst et al. 1994) found both turtles moved more than a kilometer during the study period. For this table we used 2.0 km. Disjunct individual reports from populated areas were assumed to be released pets and not included in this table.
Wood Turtle (Glyptemys insculpta) – Based on Steve Parren’s study of Wood Turtles in Vermont, males travel up to a mile (1.6 km) and females up to 1.25 miles (2 km). Based on his recommendation we used a maximum travel distance of 2.4 km (Parren, personal communication). As a result, reports greater than 4.8 km apart were considered separate sites.
Northern Map Turtle (Graptemys geographica) – A study in central Pennsylvania found that males had a linear home range along a river of 2.1 km and females had a linear home range of 1.2 km (Ernst et al. 1994). We used 2.1 km as a maximum travel distance. Lake Champlain and its tributaries hold the only known breeding populations in Vermont but they do not appear to be contiguous. Along Lake Champlain, reports greater than 4.2 km distant from the nearest site were counted as two distinct sites.
Eastern Musk Turtle (Sternotherus odoratus) – Bill Barnard’s work in Vermont showed that individual turtles traveled the length of Lake Hortonia (3.75 km). Expanding on this we used 4 km for a maximum travel distance and 8 km for a required distance between sites on the same water body with smaller water bodies counted as separate sites since this species is not known to travel extensively on land.
Eastern Box Turtle (Terrapene carolina) has not been shown to breed in Vermont and is currently considered a hypothetical species here. One issue with reports of this species is that it is frequently bought and kept as a pet and it is sometimes released far from its natural habitat. All reports of this species in Vermont outside of the southern Connecticut River Valley are assumed to be released pets and not included in this data set. The cluster of reports in the Southern Connecticut River Valley may represent a current or historic breeding population. We used a maximum territory length of 1.3km based on Ernst and Lovich (2009). As a result, two Box Turtle reports needed to be over 2.6 km apart to be considered separate sites.
Ernst, C.H. and E.M. Ernst. 2005. Snakes of the United States and Canada. Washington: Smithsonian Books.
Ernst, C.H. and J.E. Lovich. 2009. Turtles of the United States and Canada, Second Edition. Johns Hopkins University Press.
Ernst, C.H, J.E. Lovich, and R.W. Barbour. 1994. Turtles of the United States and Canada. Washington: Smithsonian Books.
Fitch, H.S. 1999. A Kansas snake community: Composition and changes over 50 years. Malabar, Florida: Krieger Publishing Co.
Gregory, P.T. and K. W. Stewart. 1975. Long distance dispersal and feeding strategy of the Red-sided Gartersnake (Thamnophis sirtalis parietalis) in the Interlake of Manitoba. Canadian Journal of Zoology 53:238-245.
Rowe, J.W. 2003. Activity and Movements of Midland Painted Turtles (Chrysemys picta marginata) Living in a Small Marsh System on Beaver Island, Michigan. Journal of Herpetology 37 (2) 342-353.
Stickel, L.F., W.H. Stickel, and F.C. Schmid. 1980. Ecology of a Maryland population of black rat snakes (Elaphe o. obsolete). American Midland Naturalist 103:1-14.