Black-Tailed Rattlesnakes
Author: Anne Schultz


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Scientific Name: Crotalus Molussus Nigresins
Common Name: Black-tailed Rattlesnake
Spanish Name: Serpiente de Cascabel Negro-atada

Description:
Adult black-tailed rattlesnakes are between 28 and 49 inches long. The background body color ranges from olive greens to yellow or gray. The snake's back (dorsal side) has unevenly shaped black patches, with a single or double patch of white scales in the center. The tail is black or dark brown, which is much different from its body. The top of the head is also a dark brown or black. Young snakes have similar coloration, but often have visible dark bands on their tails.

Geographic range:
Black-tailed rattlesnakes are found in Arizona, New Mexico, and western and central Texas. Their range extends south of the border into central Mexico.

Habitat:
These snakes are found in many habitats. In New Mexico, they are typically found in rocky, mountainous areas between 3280 feet and 10,334 feet in elevation. They may also be found in rocky stream beds or canyons.

Food Web:
Rattlesnakes are predators. They eat several different kinds of small animals. Common prey animals for black-tailed rattlers include: pocket mice, wood rats, kangaroo rats, deer mice, and fence lizards. A black-tailed rattlesnake is even known to have eaten a Gila monster that was over a foot long!

Black-tailed rattlesnakes are venomous snakes. When a snake bites, venom is injected into the victim's body through the fangs. Rattlesnake venom is a hemotoxin, meaning it mainly affects the blood and the circulatory system, which circulates the blood through the body.

Reproduction and Development:
Female black-tailed rattlesnakes bear live young. They have litters of between 3 and 6 snakes, but as many as 16 young have been found in one litter. The mother will protect her young until they have gone through their first molt (lost their skin). Offspring are usually born in July or August.

Behavior:
Black-tailed rattlesnakes are not particularly aggressive snakes, but some will rattle and prepare to strike quickly. Don't disturb them!

These snakes are known to be “sit and wait” predators. They find areas in which their potential prey are active – near rodent burrows, for example – and wait for an animal to pass by. Rattlesnakes have also been observed in trees, where they are either sunning themselves, or hunting for nesting birds .

Ecosystem roles:
Like other snakes that prey on small mammals, rattlesnakes can help people by keeping mouse populations in check. Mice and other rodents often become pests in areas where people live, particularly on farms or ranches.

Conservation:
Rattlesnakes are only offered limited protection in New Mexico by the Department of Game and Fish. People are often afraid of rattlesnakes because they are venomous. When we take time to learn about snakes, we often realize that they are interesting creatures and are not actually a threat to humans when we treat them with respect.

Cool Links: Taxonomy:

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Family: Viperidae
Genus: Crotalus
Species: Crotalus molossus

References:
Degenhardt, William G., Charles W. Painter, and Andrew H. Price. 1996. Amphibians and Reptiles of New Mexico. Albuquerque: University of New Mexico Press.

Stebbins, Robert C. 2003. A Field Guide to Western Reptiles and Amphibians. New York: Houghton Mifflin Company.