Is the black-tailed rattlesnake venomous?

The black-tailed rattlesnake is venomous. Medically significant venom requiring emergency care, even though the species is relatively even-tempered.

How do you identify a black-tailed rattlesnake?

Entirely black tail, with no banding, ahead of the rattle. Dark mask across the face between and below the eyes.

Where do black-tailed rattlesnakes live?

They are found in 3 US states, in habitats including rocky, desert and woods.

Black-tailed Rattlesnake

Venomous

Crotalus molossus · also called blacktail

The black-tailed rattlesnake is a handsome southwestern species of rocky canyons and mountain slopes. The uniformly black tail and dark facial mask identify it at a glance, and it has a reputation among herpetologists as one of the most placid rattlesnakes in the region.

Before anything else

Back away and leave it alone. A snake that can see you leaving has no reason to bite. Most bites in the United States happen to people who picked up, cornered, or tried to kill a snake.
Never handle a snake to identify it. Every identification on this site can be made from a photo or from several feet away.
If someone is bitten, call emergency services now. Keep the limb still and below the heart, remove rings and watches, and go to hospital. Do not cut, suck, apply ice, or use a tourniquet — all of these make outcomes worse.
Do not try to catch the snake for identification. A photo from a distance is enough, and hospitals treat symptoms rather than species.

In the US, the Poison Help line is 1-800-222-1222. This site is a reference, not medical advice.

Venom: Medically significant venom requiring emergency care, even though the species is relatively even-tempered.
Adult length: 28–48 inches (71–122 cm)
Markings: Olive, yellow or greenish ground with dark diamond or blotch markings, and an entirely black tail. A black mask crosses the face between the eyes.
Habitat: rocky, desert, woods
Family: pit viper
Range: 3 US states

How to identify a black-tailed rattlesnake

Entirely black tail, with no banding, ahead of the rattle.
Dark mask across the face between and below the eyes.
Olive to yellowish ground colour.
Usually found in rocky terrain rather than open sand.

What it does when it sees you

Generally calm and slow to rattle compared with diamondbacks. Still a rattlesnake and still to be given a wide berth.

What the black-tailed rattlesnake is confused with

One test settles each of these.

Timber rattlesnake →

Ranges do not overlap — timber rattlesnakes are eastern. Timber rattlers also have chevron bands rather than diamonds.

Where it lives

Arizona New Mexico Texas

Not sure it was a black-tailed rattlesnake? Identify it step by step →