Description: Crotalus willardi is a rather small rattlesnake with all subspecies measuring one to two feet in length. Color patterns are generally a dark brown base with pale or white horizontal striping, but vary slightly among subspecies. The distinctive ridges along each side of its nose, which are a series of upturned scales, are unique to this species and are the origin of one of its common names, ridge-nosed rattlesnake.

Habitat: C. willardi is rarely found outside habitats at high elevation. Wooded mountain ranges, primarily in the southwest, are where this reclusive species is found. Each subspecies’ range is limited to select mountain ranges, making human encounters rare events.

Range: The species' range extends from southeastern Arizona and extreme southwestern New Mexico south in the Sierra Madre Occidental through north-central and northeastern Sonora to western Chihuahua and (possibly disjunctly) to southern Durango and western Zacatecas, Mexico, at elevations of about 1,460 to 2,750 m.

Found in these States: AZ | NM

Venom: Due to the generally small size of C. willardi, venom discharge yields are low; thus, the largely hemotoxic venom is not as life-threatening as that of other rattlesnakes. No documented deaths have been caused by ridge-nosed rattlesnakes, but pain and discomfort can still result from a rare bite.

Diet: The diet of C. willardi includes small mammals, lizards, birds, and large centipedes. The young feed primarily on large centipedes (Scolopendra spp.) and lizards, whereas adults feed primarily on mammals and birds.

Reproduction: Like other rattlesnakes, C. willardi is ovoviviparous, meaning it gives birth and does not lay eggs. Contrasting with viviparous animals, the young still develop within an egg inside the female snake until their time of birth. Copulation occurs from late summer to early fall, and gestation lasts about four to five months. Females give birth to two to 9 (average five) young in late July or August. Both sexes appear to reach reproductive maturity around 16 inches in body (snout to vent) length. Although captive snakes have reproduced annually, wild females probably reproduce every second or third year.

Status: Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Subspecies: Five, with just two found in the United States:
   Del Nido Ridge-nosed Rattlesnake - (Crotalus willardi amabilis)
   Southern Ridge-nosed Rattlesnake - (Crotalus willardi meridionalis)
   New Mexico Ridgenose Rattlesnake - (Crotalus willardi obscurus)
   Western Chihuahuan Ridge-nosed Rattlesnake - (Crotalus willardi silus)
   Arizona Ridgenose Rattlesnake - (Crotalus willardi willardi)

Taxonomy: