Black-tailed Rattlesnake

The Black-tailed Rattlesnake, Crotalus molossus, is a species of venomous rattlesnake found in the South-Western United States and Mexico. Although they are good climbers and expert swimmers, they are mostly terrestrial and can be found in grasslands, desert areas, rocky and mountainous areas and higher altitude forested habitats.

This is a relatively small rattlesnake species. It averages between 30 and 40 inches long. The female tends to be larger than the male. Black-tailed Rattlesnakes range in color from olive green, to yellow, brown, and black. As their name implies, despite variations in body color, the tail scales are always entirely black. Occasionally these snakes 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, the Black-tailed has a rattle composed of keratin on the end of its tail. A new segment is added to the rattle each time the snake sheds its skin. In contrast, the rattle cannot be an accurate measure of the snakes age, as where it is fragile it can be easily broken during shedding. Black-tailed rattlesnakes can shed their skin several times per year.

All rattlesnakes are carnivorous, their primary food sources being rodents and other small mammals, birds, and small reptiles. Their behavior varies over the course of a year. In the spring and fall they are primarily diurnal. In the hot summer months they shift to a nocturnal behavior. During the winter months in the northern and colder part of their range they hibernate in dens created by other animals. Sometimes they will den with other species of snake.

Breeding occurs in the spring when the male follows the pheromone trail of the female. Copulation can last for hours and can occur multiple times over a period of days. After mating, the male often stays with the female for several days to prevent other snakes form mating with her. The female gives birth to live young in the summer, and the babies only stay with the mother less than a few days when they wander off on their own. Females usually breed every year giving birth to as many as 12 young, but generally averages 4 – 6. Black-tailed Rattlesnakes can live 15-20 years.

Photo by LA Dawson