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Ridge-Nosed Rattlesnakes - Crotalus willardi

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C. 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 between subspecies. The distinctive ridges along each side of its nose, which are a series of upturned scales, are unique to its genus and are the origin of its name.

Range & Habitat

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

Behavior

Rattlesnakes are primarily ambush hunters; they coil and lie waiting for prey to approach within striking distance. The diet of Crotalus willardi includes small mammals, lizards, birds, and large centipedes (Holycross et al. 2002). Young C. willardi feed primarily on large centipedes (Scolopendra sp.) and lizards, whereas adults feed primarily on mammals and birds.

Like other rattlesnakes, C. willardi is ovoviviparous, meaning it gives birth and does not lay shelled 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 approximately four to five months. Females give birth to two to nine (average 5) young in late July or August. Both sexes appear to reach reproductive maturity around 400 mm in body (snout to vent) length. Although captive snakes have reproduced annually, wild females probably reproduce every second or third year.

The Venom

Due to the general size of the snake, venom discharge yields are low; thus, the largely hemotoxic venom is not as potent as that of other rattlesnakes. There have been no documented deaths caused by Ridge-nosed rattlesnakes, but pain and discomfort can still result from a rare bite.

Subspecies

Subspecies Common name Geographic range

C. w. amabilis

Del Nido ridge-nosed rattlesnake

Mexico in north-central Chihuahua.

C. w. meridionalis

Southern ridge-nosed rattlesnake

Mexico in southern Durango and southwestern Zacatecas.

C. w. obscurus

Animas ridge-nosed rattlesnake

The United States in extreme southeastern Arizona and extreme southwestern New Mexico. Mexico in extreme northwestern Chihuahua and extreme northeastern Sonora.

C. w. silus

Chihuahuan ridge-nosed rattlesnake

Mexico in western Chihuahua and eastern Sonora.

C. w. willardi

Arizona ridge-nosed rattlesnake

The United States in southeastern Arizona, and Mexico in northern Sonora.