Crotalus molossus, commonly known as the black-tailed rattlesnake, inhabits rocky hillsides and forests in the southwestern United States and Mexico. It is recognized by its distinctive black tail and variable body coloration, ranging from olive to brown. This species is known for its potent venom and its role as both predator and prey in its ecosystem.

Crotalus molossus, commonly known as the black-tailed rattlesnake, is native to the southwestern United States and parts of Mexico. Its geographical distribution includes the states of Arizona, New Mexico, and Texas in the United States, and extends southward into Mexico, covering regions such as Sonora, Chihuahua, Durango, Zacatecas, and Sinaloa.

The black-tailed rattlesnake typically inhabits rocky hillsides, deserts, and scrublands where there is a mixture of open and covered areas. It thrives in environments featuring arid to semi-arid climates with hot summers and mild winters. The species is adaptable to a range of elevations, from lowland deserts to mountainous regions.

Crotalus molossus occupies a niche as both predator and prey within its ecosystem. It primarily feeds on small mammals, birds, and occasionally lizards, playing a crucial role in controlling the population of these species. Its presence is indicative of healthy, balanced ecosystems with sufficient prey availability. The rattlesnake's ability to thermoregulate allows it to be active during different times of the day, depending on the temperature, thereby maximizing its hunting efficiency.