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Smooth Greensnake - Opheodrys vernalis
State Rank Reason (see State Rank above)
The Smooth Green Snake is rarely observed and is only found within or near wetland habitat in far northeastern Montana. Conversion of grassland habitat to cropland threatens the species persistence within the state. Like many other reptiles we do not have data to assess changes in population, occupancy, or distribution over time.
- Details on Status Ranking and Review
Smooth Greensnake (Opheodrys vernalis) Conservation Status Review
Review Date = 05/03/2018
ScoreF - 20,000-200,000 km squared (about 8,000-80,000 square miles)
Comment20,233 square Kilometers from Natural Heritage Program range maps
ScoreU - Unknown. Long-term trend in population, range, area occupied, or number or condition of occurrences unknown
CommentNo data on trends available
ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentNo data on trends available
ScoreB - Moderate and imminent threat. Threat is moderate to severe and imminent for a significant proportion (20-60%) of the population or area.
CommentConversion of native habitat to agriculture, mortality on roads due to vehicles.
SeverityModerate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
CommentRecovery of grasslands could take over 50 years
ScopeModerate - 20-60% of total population or area affected
CommentGiven the species restricted distribution within the state, habitat changes would have a large impact on the population
ImmediacyHigh - Threat is operational (happening now) or imminent (within a year).
CommentGiven current commodity prices, conversion of sagebrush to agriculture is not profitable, but CRP acres are declining
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
CommentModerately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance within 5-20 years or 2-5 generations. Species has good dispersal ca
ScoreA - Very Narrow. Specialist. Specific habitat(s), substrate(s), food type(s), hosts, breeding/nonbreeding microhabitats, or other abiotic and/or biotic factor(s) are used or required by the Element in the area of interest, with these habitat(s) and/or other requirements furthermore being scarce within the generalized range of the species within the area of interest, and, the population (or the number of breeding attempts) expected to decline significantly if any of these key requirements become unavailable.
CommentFound only in grassland ecosystems with high densities of wetlands within the far north eastern corner of the state
Raw Conservation Status Score
3.5 + 0 (geographic distribution) + -0.5 (environmental specificity) + 0 ( trend) + -0.75 (threats) = 2.25
The Smooth Greensnake is a small to medium, slender, bright green snake with smooth dorsal scales (15 rows at mid-body), and a white or yellowish underside; each nostril is centered in a single scale; the anal scale is divided. In some regions, occasional individuals are tan, and in Texas the color may be light brown with an olive wash instead of green. Young are dark olive-gray above, hatchlings are gray to brown above; adults turn blue or gray after death. The total length is usually 30 to 51 centimeters and can reach 61 centimeters; hatchlings are about 8 to 17 centimeters long (Stebbins 2003, Conant and Collins 1991).
The Smooth Greensnake differs from the North American Racer (Coluber constrictor) by being smaller in size, in having the nostril centered in a single scale rather than placed between two scales, and in having a single anterior temporal scale on each side rather than two. It differs from the Rough Greensnake (Opheodrys aestivus) by having smooth rather than keeled dorsal scales. It differs from the Green Ratsnake (Senticolis triaspis) by having fewer dorsal scale rows (15 at mid-body vs. 25 or more) and by lacking keels on any of the dorsal scales.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
No information specific to Montana is known, but based upon habits in other areas of the species' range, the Smooth Greensnake may migrate between winter hibernaculum and summer range in some areas (Vogt 1981).
Little information is available for the species in Montana, though it has been reported from residential lawns, city parks, along ditches in prairie pothole country, and around wetland complexes. Based upon observations in other areas of its range, the Smooth Greensnake is known to occupy meadows, grassy marshes, moist grassy fields at forest edge, mountain shrublands, stream borders, bogs, open moist woodland, abandoned farmland, and vacant lots. Periods of inactivity are spent underground, beneath woody debris and rocks, or in rotting wood. They have been found hibernating in abandoned ant mounds. Most activity is restricted to the ground, but they may climb into low vegetation, and sometimes enter water (Hammerson 1999). This species may also be found in damp meadows bordering streams and lakes as well as drier, rocky areas, but usually only if grass or similar vegetation is present.
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: mtnhp.org/requests
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Human Land Use
Recently Disturbed or Modified
Sparse and Barren Systems
The primary diet is small terrestrial invertebrates (moths, caterpillars, crickets, grasshoppers, spiders, etc.). In Colorado, they are reported to also feed on small crayfish and aquatic snails (Hammerson 1999). Nothing is known regarding food habits in Montana.
This snake is active during May through September in Colorado (Hammerson 1999), and probably in Montana as well (Maxell et al. 2003), although little is known about its ecology in Montana. It is mostly diurnal. Hibernation may occur with other reptile species, and groups of 100 to 150 individuals have been found together in Manitoba and Minnesota hibernacula. Sources of mortality are poorly documented. Predators elsewhere in the range include gartersnakes. Reported predators in Montana include Loggerhead Shrike and Brown Thrasher. The first voucher specimen in the state was probably killed by hail. Considered mild-mannered, the Smooth Greensnake when handled may squirm and emit pungent, cloacal secretions.
No information specific to Montana is known. Throughout the species' range, courtship and mating behavior are poorly known. Based upon information from other locations within the species' range, females reach reproductive size in Colorado when 22 to 26 centimeters snout-vent length, or probably in about two years. Eggs are laid usually during the first three weeks of August in northern Michigan, mainly late June to late July in the Chicago, Illinois area, and July in Colorado and adjacent regions. Clutch size is 3 to 18 (generally 4 to 9). Ovipostion sites include spaces under rocks and wood, and in burrows. Eggs hatch in a few to about 30 days, early August to early September in northern Michigan, and the Black Hills of Wyoming and South Dakota; mostly early to mid-August in Chicago. Copulation has been recorded in August in Ontario. They sometimes nest communally (Fitch 1970, Hammerson 1999).
No special management activity is defined at this time. Hibernacula should not be altered or destroyed.
- Literature Cited AboveLegend: View Online Publication
- Conant, R. and J.T. Collins. 1991. A field guide to reptiles and amphibians of eastern and central North America. Third edition. Houghton Mifflin Company. Boston, MA. 450 pp.
- Fitch, H.S. 1970. Reproductive cycles of lizards and snakes. University of Kansas. Museum Natural History Miscellaneous Publication 52:1-247.
- Hammerson, G.A. 1999. Amphibians and reptiles in Colorado. University Press of Colorado & Colorado Division of Wildlife. Denver, CO. 484 p.
- Maxell, B.A., J.K. Werner, P. Hendricks, and D.L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Society for Northwestern Vertebrate Biology, Northwest Fauna Number 5. Olympia, WA. 135 p.
- Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
- Vogt, R. C. 1981. Natural history of amphibians and reptiles of Wisconsin. Milwaukee Public Museum. 205 p.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Baxter, G.T. and M.D. Stone. 1985. Amphibians and reptiles of Wyoming. Second edition. Wyoming Game and Fish Department. Cheyenne, WY. 137 p.
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- Blahnik, J.F. and P.A. Cochran. 1994. Opheodrys vernalis (smooth green snake). Herpetological Review 25(2): 77.
- Blanchard, F.N. 1933. Eggs and young of the smooth green snake, Liopeltis vernalis. Papers of the Michigan Academy of Science, Arts and Letters 27: 493-508.
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- Brunson, R.B. 1955. Check list of the amphibians and reptiles of Montana. Proceedings of the Montana Academy of Sciences 15: 27-29.
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- Collins, J.T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular 19: 41 pp.
- Cook, F.R. 1964. Communal egg laying in the smooth green snake. Herpetologica 20: 206.
- Cooper, J. G. 1869. The fauna of Montana Territory (concluded) III. Reptiles, IV Fish. American Naturalist 3(3):124-127
- Coues, E. and H. Yarrow. 1878. Notes on the herpetology of Dakota and Montana. Bulletin of the U.S. Geological Geographic Survey of the Territories 4: 259-291.
- Cox, D.L., T.J. Koob, R.P. Mecham, and O.J. Sexton. 1984. External incubation alters the composition of squamate egg-shells. Comparative Biochemistry and Physiology B Comparative Biochemisty 79(3): 481-488.
- Criddle, S. 1937. Snakes from an ant hill. Copeia 2:142.
- Crother, B.I. (ed.) 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico. SSAR Herpetological Circular No. 37:1-84.
- Cundall, D. 1986. Variations of the cephalic muscles in the colubrid snake genera Entechinus, Opheodrys, and Symphimus. Journal of Morphology 187(1): 1-21.
- DeFusco, R.P., D. Chiszar, and H.M. Smith. 1994. Liochlorophis vernalis blanchardi (smooth green snake). Herpetological Review 25(2): 77.
- Dymond, J.R. and F.E.J. Fry. 1932. Notes on the breeding habits of the green snake (Liopeltis vernalis). Copeia 2:102.
- Finch, D.M. 1992. Threatened, endangered, and vulnerable species of terrestrial vertebrates in the Rocky Mountain Region. General Technical Report RM-215. USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station, Ft. Collins CO. 38 p.
- Flath, D.L. 1998. Species of special interest or concern. Montana Department of Fish, Widlife and Parks, Helena, MT. March, 1998. 7 p.
- Fowler, J.A. 1966. A communal nesting site for the smooth green snake in Michigan. Herpetologica 22: 231.
- Gordon, D.M. and F.R. Cook. 1980. An aggregation of gravid snakes in the Quebec Laurentians. Canadian Field Naturalist 94(4): 456-457.
- Gregory, P.T. 1977a. Life history observations of three species of snakes in Manitoba. Canadian Field Naturalist 91(1): 19-27.
- Grobham, A.B. 1989. Clutch size and female length in Opheodrys vernalis. Herpetological Review 20(4): 84-85.
- Grobman, A. 1992. On races, clines, and common names in Opheodrys. Herpetological Review 23:14-15.
- Grobman, A.B. 1941. A contribution to the knowledge of variation in (Opheodrys vernalis) (Harlan), with the description of a new subspecies. Miscellaneous Publications Museum of Zoolology, University of Michigan 50: 7-38.
- Grobman, A.B. 1991. Does the smooth green snake occur in Missouri? Transactions of the Missouri Academy of Science 25(0): 1-3.
- Grobman, A.B. 1992a. Metamerism in the snake Opheodrys vernalis, with a description of a new subspecies. Journal of Herpetology 26(2): 175-186.
- Groves, John D. 1977. A note on the eggs and young of the smooth green snake, /Opheodrys vernalis/ in Maryland. Bulletin of the Maryland Herpetological Society 12(4): 131-132.
- Harlan, R. 1827. Genera of North American Reptilia, and a synopsis of the species. Journal of the Academy of National Sciences, Philadelphia 5: 317-372; 6: 7-38.
- Hayden, F.V. 1858. Catalogue of the collections in geology and natural history, obtained by the expedition under command of Lieutenant G.K. Warren, Topographical Engineers. pp. 104-105. In: F.N. Shubert (1981) Explorer on the northern plains: Lieutenant Gouverneur K. Warren's preliminary report of explorations in Nebraska and Dakota, in the years 1855-'56-'57. Engineer Historical Studies No. 2. Office of the Chief of Engineers, Washington, DC. 125 p.
- Hayden, F.V. 1862. On the geology and natural history of the upper Missouri. Transactions of the American Philosophical Society New Series 12(1): 1-218
- Hendricks, P. 1999a. Amphibian and reptile survey of the Bureau of Land Management Miles City District, Montana. Montana Natural Heritage Program, Helena, MT. 80 p.
- Hendricks, P., S. Lenard, D.M. Stagliano, and B.A. Maxell. 2013. Baseline nongame wildlife surveys on the Fort Peck Indian Reservation. Report to the Assiniboine and Sioux Tribes of the Fort Peck Indian Reservation. Montana Natural Heritage Program, Helena, MT. 83 p.
- Holman, J.A. and F. Grady. 1994. A Pleistocene herpetofauna from Worm Hole Cave, Pendleton County, West Virginia. NSS Bulletin 56(1): 46-49.
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- Hossack, B. and P.S. Corn. 2001. Amphibian survey of Medicine Lake National Wildlife Refuge Complex: 2001. USGS Northern Rocky Mountain Science Center, Aldo Leopold Wilderness Research Institute, Missoula, MT. 13 p.
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- Lachner, E.A. 1942. An aggregation of snakes and salamanders during hibernation. Copeia 4:262-263.
- Lawson, R. 1983. Opheodrys vernalis (smooth green snake). Reproduction. Herpetological Review 14(1): 20.
- Livo, L.J., D. Chiszar, and H.M. Smith. 1996. Liochlorophis (=Opheodrys) vernalis (smooth green snake). Herpetol. Rev. 27(3):154.
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- Minear, J. 1986. The nesting habits of the smooth green snake. Redstart 53(3): 113.
- Oldham, J.C. and H.M. Smith. 1987. Taxonomic significance of the intrinsic integumentary muscles of Opheodrys. Journal of the Colorado-Wyoming Academy of Science 19(1): 18.
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- Radaj, R.H. 1981. Opheodrys v. vernalis (smooth green snake). Reproduction. Herpetological Review 12: 80.
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