Federal Status:
Date Listed:
43 FR 34479; August 4, 1978.
Longer fangs than other rattlesnakes. Upturned or "pinched" internasal and canthal scales which form a ridge around the front of the snout. Relatively small body sixe. Dorsal coloration: pale cross-bands with dark edges in a grayish tan background. Resembles an oak branch.
U.S.A. (NM, AZ), Mexico. Sierra de San Luis (Sonora and Chihuahua), Animas Mountain (New Mexico), and the Peloncillo Mountains (Arizona and New Mexico). Less than 30 individuals have been documented in the Peloncillo Mtns.
Mountainous terrain at moderate elevations. Pine-Oak vegetation in sheltered canyon bottoms in NM & AZ with rocks, leaf litter, and mesic conditions. In Mexico in the central and southern parts of its range it is found on elevated plateaus.
Exhibits arboreal behavior occasionally.
Life Cycle:
Active from July through September. Ovoviviparous (female gives birth to live young which are hatched inside her oviduct). C. willardi is biennial (females mate in one summer, give birth in the next). Gestation is 13 months and young are born between August 1 and October 15. Newborns share the same space with the mother and leave within a few days. Mortality of newborns is caused by predation, lack of food and freezing. Active from late March through early October, with increased surface activity through early October. Gestation is around 5 months. Litter size averages 5-6 young. (Gestation is fetilization to birth.) Female willardi probably store male sperm until spring (late March?) when they ovulate. Birth is in August.
Adults prey primarily on small mammals and lizards, and occassionally consume birds. Juveniles prey primarily on lizards and giant centipedes.
Collecting. Alteration of habitat: type conversion via fire, cattle grazing, mining, and deforestation through logging. Predation, starvation, and disease.
Freezing may not be a real big source of martality. Probably more wothy of mention is desication due to low surface area/volume ratio combined with late or absentee monsoon rains.

graphic Andrew Rodman ©2002
July 3, 2003
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