Crotalus molossus

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iCrotalus molossus

Northern black-tailed rattlesnake, Crotalus molossus molossus

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Subfamily:	Crotalinae
Genus:	Crotalus
Species:	C. molossus

Binomial name

Crotalus molossus
Baird and Girard, 1853

Crotalus molossus is a venomous rattlesnake species found in the South-Western United States and Mexico. Its common name is the black-tailed rattlesnake. Besides the typical form, three other subspecies are known.

1 Description
2 Behavior
3 Reproduction
4 Subspecies
5 See also
6 External links

[edit] Description

C. molossus is a relatively small rattlesnake species average between 30 and 40 inches long (~75-100cm). The females tend to be larger than the males. They range in color from olive greens, to yellows, to browns, all the way to black. As their name implies, one of their most distinguishing features is that despite variations capable in body color, the tail scales are entirely black. Often these rattlesnakes have a black band that goes across their eyes and diagonally down to the corners of their mouth forming a sort of facial 'mask'.

Like other rattlesnakes, C. molossus has a rattle composed of keratin on the end of the 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.

[edit] Behavior

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 snake. They are variable in their form of locomotion depending on what substrate the need to traverse and will actively change between sidewinding or rectilinear movement. Although they are able climbers and expert swimmers, C. molossus is primarily a terrestrial species and inhabits grasslands, desert areas, rocky and mountainous areas, as well as higher altitude forested habitats.

[edit] Reproduction

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 months, and the babies only 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 averages 4-6. Their lifespan averages 15-20 years.

[edit] Subspecies

Subspecies	Authority	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 and Girard, 1853	Northern black-tailed rattlesnake	United States (Arizona, New Mexico, South-West Texas), Mexico
C. m. nigrescens	Gloyd, 1936	Mexican black-tailed rattlesnake	Mexico (South Sonora, South-West Chihuahua, South Coahuila, south to Oaxaca and Veracruz, Tlaxcala)
C. m. oaxacus	Gloyd, 1948	Oaxacan black-tailed rattlesnake	Mexico (Oaxaca)