Coluber bilineatus - (Jan, 1863)
Sonoran Whipsnake
Synonym(s): Masticophis bilineatus Jan, 1863
Taxonomic Status: Accepted
Related ITIS Name(s): Masticophis bilineatus Jan, 1863 (TSN 174237)
Unique Identifier: ELEMENT_GLOBAL.2.104217
Element Code: ARADB21010
Informal Taxonomy: Animals, Vertebrates - Reptiles - Snakes
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Reptilia Squamata Colubridae Coluber
Genus Size: A - Monotypic genus
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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: Masticophis bilineatus
Taxonomic Comments: Subspecies lineolatus was proposed as a distinct species by Collins (1991), but no supporting data were presented. Camper and Dixon (1994) concluded that none of the nominal subspecies of C. bilineatus are worthy of recognition, and they regarded the species as monotypic. Populations south of the Rio Fuerte in northern Sinaloa have relatively low numbers of ventral scales and may be described as a distinct subspecies (C. H. Lowe, pers. comm., cited by Camper 1996). However, scale counts may be affected by conditions during embryonic development; genetic data are needed to determine whether this variation has phylogenetic significance.

Crother et al. (in Crother 2008, 2012) cited published studies in transferring all Masticophis species to the genus Coluber, but they also stated that there is unpublished evidence that might reject this.
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 05Dec2005
Global Status Last Changed: 30Oct1996
Rounded Global Status: G5 - Secure
Nation: United States
National Status: N5 (09Jan1997)

U.S. & Canada State/Province Status
United States Arizona (S5), New Mexico (S3)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: The range extends from central Arizona to extreme southwestern New Mexico and south through western Mexico to Colima, Mexico, with an eastward extension onto the Mexican Plateau in Jalisco, Aguascalientes, and Zacatecas (Camper and Dixon 1994, Camper 1996). Camper and Dixon regarded records from Isla San Pedro Martir, Coahuila, and Oaxaca as erroneous. Elevational range extends to 2,300 meters (Camper 1996).

Number of Occurrences: 81 - 300
Number of Occurrences Comments: This species is represented by a large number of occurrences or subpopulations. Camper (1996) mapped over 200 collection sites.

Population Size: 100,000 - 1,000,000 individuals
Population Size Comments: Total adult population size is unknown but likely exceeds 100,000. This snake is relatuvely common in many areas of suitable habitat.

Overall Threat Impact: Low
Overall Threat Impact Comments: No major threats are known. The habitat often is unsuitable for most incompatible human uses.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable.

Long-term Trend: Decline of <30% to increase of 25%

Intrinsic Vulnerability: Moderately vulnerable

Other NatureServe Conservation Status Information

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range extends from central Arizona to extreme southwestern New Mexico and south through western Mexico to Colima, Mexico, with an eastward extension onto the Mexican Plateau in Jalisco, Aguascalientes, and Zacatecas (Camper and Dixon 1994, Camper 1996). Camper and Dixon regarded records from Isla San Pedro Martir, Coahuila, and Oaxaca as erroneous. Elevational range extends to 2,300 meters (Camper 1996).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AZ, NM

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)
AZ Pima (04019)
NM Catron (35003), Hidalgo (35023)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
15 Animas Valley (15040003)+, San Francisco (15040004)+, Rio Sonoyta (15080102)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Reproduction Comments: Lays a clutch of 6-13 eggs, June-July (Stebbins 1985).
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Palustrine Habitat(s): Riparian
Terrestrial Habitat(s): Bare rock/talus/scree, Desert, Shrubland/chaparral, Woodland - Conifer, Woodland - Mixed
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Habitats include semiarid lower mountain slopes, with growth of grass, saguaro cactus, paloverde, and ocotillo, and extend through chaparral and juniper into pine-oak belt in mountains (Stebbins 2003); desert, grassland, and montane forest habitats (Camper 1996), often found along rocky streams. This snake is basically terrestrial but also climbs in vegetation.
Adult Food Habits: Carnivore
Immature Food Habits: Carnivore
Food Comments: Eats bird nestlings, lizards, and frogs.
Adult Phenology: Diurnal, Hibernates/aestivates
Immature Phenology: Diurnal, Hibernates/aestivates
Phenology Comments: Inactive in cold temperatures and extreme heat.
Length: 170 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: 05Dec2005
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 05Dec2005
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
Help
  • 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.

  • Camper, J. D. 1996. MASTICOPHIS BILINEATUS. Catalogue of American Amphibians and Reptiles 637.1-637.4.

  • Camper, J. D., and J. R. Dixon. 1994. Geographic variation and systematics of the striped whipsnakes (MASTICOPHIS TAENIATUS complex; Reptilia: Serpentes: Colubridae). Annals of Carnegie Museum 63(1):1-48.

  • 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.

  • Collins, J. T. 1991. Viewpoint: a new taxonomic arrangement for some North American amphibians and reptiles. SSAR Herpetol. Review 22:42-43.

  • 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.

  • Crother, B. I., J. Boundy, F. T. Burbrink, and J. A. Campbell. 2008. Squamata: Snakes. IN B. I. Crother (ed.), Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, pp. 46-65 SSAR Herpetological Circular 37.

  • Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and reptiles of New Mexico. University of New Mexico Press, Albuquerque. xix + 431 pp.

  • Dowling, H. G. 1993. Viewpoint: a reply to Collins (1991, 1992). Herpetol. Rev. 24:11-13.

  • Stebbins, R. C. 1985a. A field guide to western reptiles and amphibians. Second edition. Houghton Mifflin Company, Boston, Massachusetts. xiv + 336 pp.

  • Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. Third edition. Houghton Mifflin Company, Boston.

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