Photo credit:

Eric Centenero Alcala

Common name

Mexican Black-tailed Rattlesnake

Scientific name

Crotalus molossus nigrescens

Conservation Status

Least Concern

Federal and State Protections

Countries of Occurrence


States or Providence 


Adult size

Species Description

This beautiful, large rattlesnake ranges throughout most of Mexico. The Mexican black-tailed rattlesnake occurs in rocky hillsides and other montane habitats. It is active year-round but can more commonly be found during the spring and summer months around the breeding season. The diet of adults primarily consists of small mammals.

Fun fact: Juveniles and adults of this species have different venom compositions. Juveniles have a crotamine-like myotoxin which causes limb paralysis in prey; adults lack this myotoxin completely! Juveniles need this addition to their venom to help catch prey and grow in size. Adults, on the other hand, have venom that prioritizes pre-digestion.

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