The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2008: T63997A12728524
Trimorphodon vilkinsonii, Chihuahuan Lyre Snake
Assessment by: Frost, D.R., Hammerson, G.A. & Santos-Barrera, G.
View on www.iucnredlist.org
Citation: Frost, D.R., Hammerson, G.A. & Santos-Barrera, G. 2007. Trimorphodon vilkinsonii. The
IUCN Red List of Threatened Species 2007: e.T63997A12728524.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
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THE IUCN RED LIST OF THREATENED SPECIES™
Taxonomy
Kingdom
Phylum
Class
Order
Family
Animalia
Chordata
Reptilia
Squamata
Colubridae
Taxon Name: Trimorphodon vilkinsonii Cope, 1886
Synonym(s):
• Trimorphodon biscutatus subspecies vilkinsonii Cope, 1886
Common Name(s):
• English:
Chihuahuan Lyre Snake, Chihuahuan Desert Lyresnake, Texas Lyre Snake
Taxonomic Notes:
Using morphological data, LaDuc and Johnson (2003) reevaluated the status of T. biscutatus lambda and
T. biscutatus vilkinsonii and concluded that the latter should be regarded as a distinct species (T.
vilkinsonii). They found that specimens from Cochise County, Arizona, and Hidalgo County, New Mexico,
deemed by Gehlbach as intermediate between T. b. lambda and T. b. vilkinsonii, instead should be
regarded as T. b. lambda.
Assessment Information
Red List Category & Criteria:
Least Concern ver 3.1
Year Published:
2007
Date Assessed:
March 1, 2007
Justification:
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is
unlikely to be declining fast enough to qualify for listing in a more threatened category.
Geographic Range
Range Description:
The species' range encompasses southwestern New Mexico (west to the Florida and Tres Hermanas
mountains), western Texas, and adjacent Chihuahua and Coahuila in northeastern Mexico, at elevations
ranging from at least 860 to 1,856 m asl (LaDuc and Johnson 2003). The range probably includes many
of the Mexican mountain ranges bordering the Rio Grande (Rio Bravo) throughout Chihuahua and to the
Sierra del Carmen in western Coahuila, in addition to other uncollected intervening areas between
Ciudad Chihuahua and the United States border (LaDuc and Johnson 2003).
Country Occurrence:
Native: Mexico; United States
© The IUCN Red List of Threatened Species: Trimorphodon vilkinsonii – published in 2007.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
1
Distribution Map
© The IUCN Red List of Threatened Species: Trimorphodon vilkinsonii – published in 2007.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
2
Population
Degenhardt et al. (1996) mapped nine collection sites in New Mexico. Werler and Dixon (2000) mapped
about 30 collection sites in Texas. These represent roughly 14 to 15 distinct occupied areas in addition to
those in Mexico. Secretive habits and occurrence in rough terrain make it likely that this snake occurs in
substantially more locations than are presently known.
The total adult population size is unknown but presumably exceeds 10,000 and is probably much larger.
Though often regarded as rare, this secretive snake is fairly common in some areas (e.g., McCrystal
1991) and is probably generally more numerous than available records indicate.
Its extent of occurrence, area of occupancy, number of subpopulations, and population size are
probably relatively stable.
Current Population Trend: Stable
Habitat and Ecology (see Appendix for additional information)
This snake occurs most commonly in dry, rocky terrain of mountains, canyons, hills, rock outcrops,
fissured bluffs, and arroyos, in areas with desert plants (e.g., ocotillo, catclaw mimosa, white thorn,
yucca, lechuguilla, prickly pear, cholla, and grasses) or riparian vegetation (e.g., ash, hackberry, juniper,
oak), sometimes on desert flats dominated by creosote bush or in shallow canyons with mesquite
(Degenhardt et al. 1996, Tennant 1998, Werler and Dixon 2000, LaDuc and Johnson 2003).
Systems: Terrestrial
Threats
No major threats to this species are known.
Conservation Actions (see Appendix for additional information)
Several occurrences of this species are in protected areas. Its distribution in Mexico needs further study
(LaDuc and Johnson 2003).
Credits
Assessor(s):
Frost, D.R., Hammerson, G.A. & Santos-Barrera, G.
Reviewer(s):
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating
Team)
© The IUCN Red List of Threatened Species: Trimorphodon vilkinsonii – published in 2007.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
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Bibliography
Degenhardt, W.G., Painter, C.W. and Price, A.H. 1996. Amphibians and Reptiles of New Mexico.
University of New Mexico Press, Albuquerque, New Mexico. Xix + 431 pp.
IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed:
12th September 2007).
LaDuc, T.J. and Johnson, J.D. 2003. A taxonomic revision of Trimorphodon biscutatus vilkinsonii
(Serpentes: Colubridae). Herpetologica 59: 364-374.
McCrystal, H.K. 1991. The herpetofauna of the Big Bend region. Sonoran Herpetologist 9(4): 137-141.
Tennant, A. 1998. A Field Guide to Texas Snakes. Second edition. Gulf Publishing Company, Houston,
Texas.
Werler, J.E. and Dixon, J.R. 2000. Texas Snakes: Identification, Distribution, and Natural History.
University of Texas Press, Austin, Texas.
Citation
Frost, D.R., Hammerson, G.A. & Santos-Barrera, G. 2007. Trimorphodon vilkinsonii. The IUCN Red List of
Threatened Species 2007: e.T63997A12728524.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
Disclaimer
To make use of this information, please check the Terms of Use.
External Resources
For Images and External Links to Additional Information, please see the Red List website.
© The IUCN Red List of Threatened Species: Trimorphodon vilkinsonii – published in 2007.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
4
Appendix
Habitats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Habitat
Season
Suitability
Major
Importance?
0. Root -> 6. Rocky areas (eg. inland cliffs, mountain peaks)
-
Suitable
-
8. Desert -> 8.1. Desert - Hot
-
Suitable
-
8. Desert -> 8.2. Desert - Temperate
-
Suitable
-
Conservation Actions in Place
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Actions in Place
In-Place Land/Water Protection and Management
Occur in at least one PA: Yes
Research Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Research Needed
0. Root -> 100.2. OLD 3-Research actions
1. Research -> 1.1. Taxonomy
1. Research -> 1.2. Population size, distribution & trends
© The IUCN Red List of Threatened Species: Trimorphodon vilkinsonii – published in 2007.
http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63997A12728524.en
5
The IUCN Red List Partnership
The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species
Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership. The IUCN
Red List Partners are: BirdLife International; Botanic Gardens Conservation International; Conservation
International; Microsoft; NatureServe; Royal Botanic Gardens, Kew; Sapienza University of Rome; Texas
A&M University; Wildscreen; and Zoological Society of London.
THE IUCN RED LIST OF THREATENED SPECIES™