Thamnophis brachystoma - (Cope, 1892)
Short-headed Gartersnake
Other English Common Names: Short-headed Garter Snake, Shorthead Garter Snake
Taxonomic Status: Accepted
Related ITIS Name(s): Thamnophis brachystoma (Cope, 1892) (TSN 174138)
Unique Identifier: ELEMENT_GLOBAL.2.104011
Element Code: ARADB36010
Informal Taxonomy: Animals, Vertebrates - Reptiles - Snakes
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Reptilia Squamata Colubridae Thamnophis
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
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Concept Reference: 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 No. 19. 41 pp.
Concept Reference Code: B90COL01NAUS
Name Used in Concept Reference: Thamnophis brachystoma
Conservation Status
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NatureServe Status

Global Status: G4
Global Status Last Reviewed: 05Sep2006
Global Status Last Changed: 10Jul1998
Rounded Global Status: G4 - Apparently Secure
Reasons: Small range in New York and Pennsylvania (and introduced in Ohio); population densities maybe lower than historical numbers, but believed to be maintaining a steady population density; several introduced populations have become established; apparently secure.
Nation: United States
National Status: N4 (05Oct1996)

U.S. & Canada State/Province Status
United States New York (S3), Ohio (SNR), Pennsylvania (S3)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 5000-20,000 square km (about 2000-8000 square miles)
Range Extent Comments: The native range includes southwestern New York and northwestern Pennsylvania, mainly in the unglaciated portions of the upper Allegheny River drainage, at elevations of 270 to over 700 meters (Ernst and Barbour 1989, Rossman et al. 1996, Ernst and Ernst 2003). This species is introduced and established at Pittsburgh and apparently also in Butler, Clearfield, and Erie counties (e.g., Lethaby, 2004, Herpetol. Rev. 35:73), Pennsylvania, in south-central New York (Conant and Collins 1991), and in Youngstown, Mahoning County, Ohio (Novotny, 1990, Herpetol. Rev. 21:42). In New York, this snake is restricted to the Allegheny River drainage in Chatagua, Cattaraugus, and Allegheny counties and two isolated (possibly introduced) areas at Horseheads straddling the Susquehanna and St. Lawrence river drainages, Chemung County (Bothner 1986).

Number of Occurrences: 21 - 300
Number of Occurrences Comments: This species is represented by a large number of occurrences (subpopulations). Bothner (1976) mapped 69 records in New York and Pennsylvania and five questionable records. McCoy (1982) mapped 73 records in 11 counties from Pennsylvania. Hulse et al. (2001) mapped 70+ collection sites in Pennsylvania plus 9 additonal locations with established introductions.

Population Size: 10,000 - 1,000,000 individuals
Population Size Comments: Adult population size is unknown but presumably exceeds 10,000. This snake is common to abundant in its small range (Harding 1997, Hulse et al. 2001).

Overall Threat Impact: Medium
Overall Threat Impact Comments: In some areas the preferred habitat has disappeared as old farms have been developed or abandoned and reforested (Bothner 1986). It has been suggested that Thamnophis sirtalis may be encroaching on the range of T. brachystoma in some reforested areas (Bothner 1986), but whether or not this poses a threat independent of that associated with habitat change is unknown.

This species becomes established easily when introduced in suitable areas in urban settings outside the natural range (McCoy 1982). However, it disappears from areas that have undergone intensive development.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Current trend is uncertain, but extent of occurrence, area of occupancy, number of subpopulations, and populations size probably are relatively stable (see Bothner 1986) or declining at a rate of less than 10 percent over 10 years or three generations. This species appears to be common and secure within Pennsylvania. Large populations have become established through translocations outside of the native range (Hulse et al. 2001).

Long-term Trend: Decline of <30% to increase of 25%
Long-term Trend Comments: Early references commented on high population densities, while Bothner (1976) commented on drastic declines, yet this species remains locally abundant in many areas.

Other NatureServe Conservation Status Information

Inventory Needs: Obtain current information on abundance, monitor population trends, and determine if any threats exist.

Distribution
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Global Range: (5000-20,000 square km (about 2000-8000 square miles)) The native range includes southwestern New York and northwestern Pennsylvania, mainly in the unglaciated portions of the upper Allegheny River drainage, at elevations of 270 to over 700 meters (Ernst and Barbour 1989, Rossman et al. 1996, Ernst and Ernst 2003). This species is introduced and established at Pittsburgh and apparently also in Butler, Clearfield, and Erie counties (e.g., Lethaby, 2004, Herpetol. Rev. 35:73), Pennsylvania, in south-central New York (Conant and Collins 1991), and in Youngstown, Mahoning County, Ohio (Novotny, 1990, Herpetol. Rev. 21:42). In New York, this snake is restricted to the Allegheny River drainage in Chatagua, Cattaraugus, and Allegheny counties and two isolated (possibly introduced) areas at Horseheads straddling the Susquehanna and St. Lawrence river drainages, Chemung County (Bothner 1986).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States NY, OH, PA

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted.

Range Map Compilers: NatureServe, 2005


U.S. Distribution by County Help
State County Name (FIPS Code)
PA Clearfield (42033), Crawford (42039), Elk (42047), Erie (42049), Forest (42053), Jefferson (42065), McKean (42083), Mercer (42085), Potter (42105), Venango (42121), Warren (42123)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Sinnemahoning (02050202)+
04 Chautauqua-Conneaut (04120101)+
05 Upper Allegheny (05010001)+, Conewango (05010002)+, Middle Allegheny-Tionesta (05010003)+, French (05010004)+, Clarion (05010005)+, Middle Allegheny-Redbank (05010006)+, Connoquenessing (05030105)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A colubrid snake; adults usually about 36-46 cm long.
Diagnostic Characteristics: Differs from THAMNOPHIS SIRTALIS in usually lacking a longitudinal series of black spots between the dorsal and lateral stripes. Differs from THAMNOPHIS BUTLERI in having a shorter head and 17 scale rows at mid-body (vs. usually 19).
Reproduction Comments: Mating occurs in spring. Litters of 5-14 young are born late July-September (Behler and King 1979), mostly in August. Sexually mature in second year. Mature females do not produce young every year.
Ecology Comments: Commonly aggregates under cover objects.
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Terrestrial Habitat(s): Forest Edge, Grassland/herbaceous, Old field
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Habitats include old fields, meadows, pastures, forest edges, and other open herbaceous fields, often in areas close to water or wetlands; this snake scarcely penetrates wooded areas; it can be found active or basking on the ground or in stone piles or under debris (Rossman et al. 1996, Hulse et al. 2001, Ernst and Ernst 2003). Introduced populations are well established in urban settings. Hibernating individuals have been found underground on a steep rocky slope.
Adult Food Habits: Carnivore, Invertivore
Immature Food Habits: Carnivore, Invertivore
Food Comments: Diet is exclusively, or nearly exclusively, earthworms (Ernst and Barbour 1989).
Adult Phenology: Hibernates/aestivates
Immature Phenology: Hibernates/aestivates
Length: 56 centimeters
Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation
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Group Name: Medium And Large Colubrid Snakes

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs) in or near appropriate habitat where the species is presumed to be established and breeding.
Separation Barriers: Busy highway or highway with obstructions such that snakes rarely if ever cross successfully; major river, lake, pond, or deep marsh (this barrier pertains only to upland species and does not apply to aquatic or wetland snakes); densely urbanized area dominated by buildings and pavement.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Available information on movements of colubrid snakes is limited to a small minority of species. These data indicate that nearly all species have home ranges smaller or much smaller than 25 ha (e.g., less than 3 ha, Pituophis catenifer in California, Rodriguez-Robles 2003), with some up to about 75 ha (Heterodon platirhinos, average 50 ha, Plummer and Mills 2000), and the largest up to 225 ha in the biggest colubrids (Drymarchon, summer mean 50-100 ha, USFWS 1998).

Radiotelemetry data for Pantherophis indicate that residents of hibernacula that are 1-2 km apart (with suitable intervening habitat) probably interbreed (Prior et al. 1997, Blouin-Demers and Weatherhead 2002). However, "evidence of genetic structure even over short distances (e.g., 2-20 km) implies that gene flow among rat snake populations can be easily disrupted" (Prior et al. 1997). Loughheed et al. (1999) found evidence of substantial genetic exchange among local hibernacula (< 6 km apart), but gene flow over distances of 10s of km appears to be substantially less. Based on extensive radio-tracking data, Blouin-Demers and Weatherhead (2002) found that home range size of Pantherophis averaged 18.5 ha and ranged up to 93 ha; based on the most mobile individuals, Pantherophis from hibernacula up to 8 km apart can come together for mating. Pantherophis and probably other colubrids exhibit high fidelity to hibernacula and shift even to nearby sites only rarely (Prior et al. 2001).

Many of the several studies that report small home ranges for colubrids did not employ methods (e.g., radio telemetry) suitable for detecting full annual or multi-annual home range size, dispersal, or other long-distance movements, so these may have yielded underestimates of home ranges or activity areas.

At least some colubrids, including medium-sized species such as garter snakes, not uncommonly move between areas up to a few kilometers apart, and several species make extensive movements of up to several kilometers, so separation distances of 1-2 km for suitable habitat are too small for medium-sized and large colubrids.

A separation distance of 10 km for suitable habitat was selected as most appropriate for snakes assigned to this Specs Group because it seems generally unlikely that two locations separated by less than 10 km of suitable habitat would represent distinct occurrences.

For the purposes of these occurrence specifications, upland habitat is regarded as unsuitable habitat for aquatic and wetland snakes. For upland snakes, shallow or patchy wetlands are treated as unsuitable habitat whereas large deepwater habitats (subjective determination) are barriers.

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Date: 12Feb2013
Author: Hammerson, G.
Notes: Separation distance for suitable habitat was changed from 5 km to 10 km based on comments from Dale Jackson (12 Feb 2013).
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 05Sep2006
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 05Sep2006
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Behler, J. L., and F. W. King. 1979. The Audubon Society field guide to North American reptiles and amphibians. Alfred A. Knopf, New York. 719 pp.

  • Bothner, R. C. 1976. Thamnophis brachystoma. Cat. Am. Amph. Rep. 190.1-190.2.

  • Bothner, R. C. 1986. A survey of the New York state populations of the short-headed garter snake, THAMNOPHIS BRACHYSTOMA (Cope) (REPTILIA: COLUBRIDAE). Unpulished report for the New York State Engangered Species Unit. Contract no. Coo1340.

  • 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 No. 19. 41 pp.

  • Conant, R. and J. T. Collins. 1991. A field guide to reptiles and amphibians: eastern and central North America. Third edition. Houghton Mifflin Co., Boston, Massachusetts. 450 pp.

  • Conant, R., and J. T. Collins. 1998. A field guide to reptiles and amphibians: eastern and central North America. Third edition, expanded. Houghton Mifflin Co., Boston, Massachusetts. 616 pp.

  • Crother, B. I. (editor). 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Sixth edition. Society for the Study of Amphibians and Reptiles Herpetological Circular 37:1-84. Online with updates at: http://www.ssarherps.org/pages/comm_names/Index.php

  • Crother, B. I. (editor). 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 7th edition. SSAR Herpetological Circular 39:1-92.

  • Ernst, C. H., and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.

  • Ernst, C. H., and R. W. Barbour. 1989. Snakes of eastern North America. George Mason Univ. Press, Fairfax, Virginia. 282 pp.

  • Harding, J. H. 1997. Amphibians and reptiles of the Great Lakes region. University of Michigan Press, Ann Arbor. xvi + 378 pp.

  • Hulse, A. C., C. J. McCoy, and E. Censky. 2001. Amphibians and reptiles of Pennsylvania and the Northeast. Comstock Publishing Associates, Cornell University Press, Ithaca. 419 pp.

  • Lawson, R. 1987. Molecular studies of thamnophiine snakes: 1. The phylogeny of the genus NERODIA. J. Herpetology 21:140-157.

  • McCoy, C. J. 1982. Amphibians and reptiles of Pennsylvania. Carnegie Musuem of Natural History, Special publication 6.

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