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Crotalus molossus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA VIPERIDAE

Scientific Name: Crotalus molossus
Species Authority: Baird & Girard, 1853
Common Name(s):
English Black-tailed Rattlesnake, Blacktail Rattlesnake

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Hammerson, G.A., Vazquez Díaz, J. & Quintero Díaz, G.E.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
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 [top]

Range Description: The species' range extends from western, central, and southern Arizona, central and southern New Mexico, and southwestern and central Texas in the United States, south through Mexico to the southern edge of the Mexican Plateau and Mesa del Sur (Oaxaca), including Isla Tiburon in the Gulf of California, at elevations from near sea level up to around 2,930 m asl (9,600 feet) (Grismer 2002, Stebbins 2003, Campbell and Lamar 2004).
Countries:
Native:
Mexico; United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species is represented by a large number of occurrences (subpopulations). On a range-wide scale, Campbell and Lamar (2004) mapped more than 200 collection sites. The adult population size is unknown but presumably exceeds 100,000. It is common in Mexico and in some areas of the United States. Its extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at less than 10% over 10 years or three generations.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: The species' habitat includes rocky areas (rock slides, outcrops, canyon slopes, areas near cliff, stream courses), with vegetation ranging from arid tropical scrub, tropical deciduous forest, mixed boreal-tropical forest, paloverde-cactus-thorn bush associations, oak-grass savanna, and mesquite grasslands to chaparral and the pine-oak and pine-fir belts (Werler and Dixon 2000, Ernst and Ernst 2003, Stebbins 2003, Campbell and Lamar 2004). In Arizona and northern Mexico, this snake often occurs in rocky areas in pine-oak association. A population in southeastern Arizona frequented rocky areas but used arroyos (dry creeks) and creosote bush flats in late summer and autumn (fall) (Beck 1995). Other habitats include creosote bush-covered hills, grassy prairie, giant-dagger flats, and the vicinity of abandoned buildings (Tennant 1984). This species occupies a wide range of habitats in Mexico, where at the southern end of the range habitats include pine-oak, oak savanna, sweet-gum/oak forest, and mesquite grassland (Armstrong and Murphy 1979). Refuges during inactivity include rock crevices, caves, animal burrows, or wood rat houses. This snake is mostly terrestrial but sometimes climbs into trees or bushes.
Systems: Terrestrial

Threats [top]

Major Threat(s): No major threats to this species are known.

Conservation Actions [top]

Conservation Actions: Many occurrences of this species are in protected areas.

Citation: Hammerson, G.A., Vazquez Díaz, J. & Quintero Díaz, G.E. 2007. Crotalus molossus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 23 October 2014.
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