Brandon La Forest (HERP.MX)
New Mexico Ridge-nosed Rattlesnake
Crotalus willardi obscurus
Federal and State Protections
Federally listed as threatened. State protected in Arizona. State listed as Endangered in New Mexico.
Countries of Occurrence
United States of America and Mexico
States or Providence
USA: Arizona, New Mexico; Mexico: Sonora and Chihuahua
Cochise (AZ), Hidalgo (NM)
The New Mexico Ridge-nosed Rattlesnake is a small, montane, rattlesnake restricted to a narrow range of mountain ranges in the desert southwest of the United States and Mexico. The Ridge-nosed rattlesnake complex consists of five subspecies that can be clearly identified from genetic and phenotypic markings. The New Mexico Ridge-nosed Rattlesnake can be identified by the lack of a "white flash mark" on the side of the head and lack of white vertical line on the rostral (in-between the nares) or mental scale (scale directly in the center of the bottom jaw.
The drab coloration of the New Mexico Ridge-nosed Rattlesnake is liken to their habitat, where they occur in narrow stretches of suitable habitat. In the Animas Mountains, they are known to occur in areas of semi-evergreen oaks (Quercus sp.), conifers, and other tree-shrub combinations. The species is known to brumate in talus slides and will surface periodically for water on warm days.
The diet of the New Mexico Ridge-nosed Rattlesnake was recently more thoroughly investigated (Holycross et al. 2002). The principle diet of the ridge-nosed rattlesnake consists of rodents (Peromyscus spp.) and lizards (primarily Sceloporus spp.); although like some other small snakes, they do consume centipedes! Other incidental prey they have been recorded consuming includes birds and other small mammals.