Crotalus molossus

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Crotalus molossus
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Subfamily: Crotalinae
Genus: Crotalus
Species: C. molossus
Binomial name
Crotalus molossus
Baird & Girard, 1853
Synonyms
  • Crotalus molossus
    Baird & Girard, 1853
  • Crotalus ornatus Hallowell, 1854
  • Caudisona molossusCope, 1860
  • C[audisona]. molossa
    – Cope, 1867
  • [Crotalus durissus] Var. molossusGarman, 1884
  • Crotalus terrificus
    Boulenger, 1896 (part)
  • Crotalus molossus molossus
    Gloyd, 1936[1]
Common names: black-tailed rattlesnake, green rattler,[2] Northern black-tailed rattlesnake.[3]

Crotalus molossus is a venomous pit viper species found in the southwestern United States and Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.[4]

Description[edit]

C. m. molossus

This medium-sized species[2] averages from 76 to 107 cm (30 to 42 in) in length.[5] Large specimens are usually not much more than 100 cm (39 in) long, although lengths of 125.0 cm (49.2 in) (Gloyd, 1940), 125.7 cm (49.5 in) (Klauber, 1972), and 129.5 cm (51.0 in) (Shaw & Campbell, 1974) have been reported.[2] The females tend to be larger than the males.

They range in color from yellows and olive greens to browns and black. As their name implies, one of their most distinguishing features is, despite variations in body color, the tail scales are entirely black. Often, this rattlesnake has a black band across its eyes and diagonally down to the corners of its mouth, forming a sort of facial 'mask'.

Like other rattlesnakes, C. molossus has a rattle composed of keratin on the end of its tail. Each time the snake sheds its skin, a new segment is added to the rattle. They can shed their skin several times a year, and the rattle is fairly fragile and can be broken, so the length of a rattlesnake's rattle is not an accurate measure of its age, unless the terminal button is intact.

Geographic range[edit]

It is found in the southwestern United States in Arizona, New Mexico and west and central Texas, and Mexico as far south as Oaxaca. Also it is found in the Gulf of California on San Estéban and Tiburón Islands. The distribution reaches a maximum elevation of 2930 m. The type locality given is "Fort Webster, St. Rita del Cobre, N. Mex." (Fort Webster, Santa Rita del Cobre, Grant County, New Mexico, USA).[1]

Conservation status[edit]

This species is classified as Least Concern IUCN Red List of Threatened Species (v3.1, 2001).[6] Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2007.[7]

Behavior[edit]

CrotalusMolossus.jpg

All rattlesnakes are carnivorous, their primary food sources being rodents, other small mammals, birds, and small reptiles. The behavior of northern black-tailed rattlesnakes varies over the course of a year. In the spring and fall, they are primarily diurnal. In the summer, they shift to a nocturnal behavior, to avoid the heat of summer. In the winter, they hibernate in dens created and abandoned by other animals, often with other species of snakes. They are variable in their form of locomotion depending on what substrate they need to traverse and will actively change between sidewinding or rectilinear movement. Although it is an able climber and expert swimmer, C. molossus is primarily a terrestrial species and inhabits grasslands, desert areas, and rocky and mountainous areas, as well as high-altitude forested habitats.

Reproduction[edit]

Breeding occurs in the spring when males follow the pheromone trails of the females. Copulation can sometimes last for hours and happen multiple times over a period of days. After mating, the male often stays near the female for several days to prevent any other males from mating with her. The female gives birth to live young in the summer, and the babies stay with the mother only until they wander off on their own, usually less than a day or two. Females are believed to breed every year, and can have litters as large as 10-12 young, but usually average four to six. Their lifespans average 15–20 years.

Subspecies[edit]

Subspecies[4] Taxon author[4] Common name Geographic range
C. m. estebanensis Klauber, 1949 San Esteban Island black-tailed rattlesnake Mexico: Isla San Esteban (Gulf of California)
C. m. molossus Baird & Girard, 1853 Northern black-tailed rattlesnake United States (Arizona, New Mexico, southwest Texas), Mexico
C. m. nigrescens Gloyd, 1936 Mexican black-tailed rattlesnake Mexico (South Sonora, southwest Chihuahua, southern Coahuila, south to Oaxaca and Veracruz, Tlaxcala)
C. m. oaxacus Gloyd, 1948 Oaxacan black-tailed rattlesnake Mexico (Oaxaca)

See also[edit]

References[edit]

  1. ^ a b McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
  2. ^ a b c Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  3. ^ Wright AH, Wright AA. 1957. Handbook of Snakes of the United States and Canada. Comstock Publishing Associates. Ithaca and London. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.
  4. ^ a b c "Crotalus molossus". Integrated Taxonomic Information System. Retrieved 24 February 2007. 
  5. ^ Conant R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Second Edition. [First published in 1958]. Houghton Mifflin Company. Boston. 429 pp. 48 plates. ISBN 0-395-19979-4 (hc), ISBN 0-395-19977-8 (pb).
  6. ^ Crotalus molossus at the IUCN Red List. Accessed 13 September 2007.
  7. ^ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.

External links[edit]