New Mexican Ridge-Nosed rattlesnake (Crotalus willardi obscurus)
Where Listed: WHEREVER FOUND
This is a small (maximum length 66 cm) montane species that is usually pale gray to gray-brown and does not have prominent facial markings. The back is marked with pale crossbars lined with darker coloration along the front and back edges. The underside is cream to white with occasional mottling of grayish to reddish brown.Young have dark gray/black or light yellow tails.
- States/US Territories in which the New Mexican Ridge-Nosed rattlesnake, Entire is known to or is believed to occur: Arizona , New Mexico
- US Counties in which the New Mexican Ridge-Nosed rattlesnake, Entire is known to or is believed to occur: View All
- Countries in which the the New Mexican Ridge-Nosed rattlesnake, Entire is known to occur: Mexico
- Additional species information
|Status||Date Listed||Lead Region||Where Listed|
|08/21/1978||Southwest Region (Region 2)||Entire|
» Federal Register Documents
|05/26/1977||42 FR 27007 27009||Proposed Endangered Status and Critical Habitat for New Mexico Ridge-Nosed Rattlesnake; 42 FR 27007 27009 (Crotalus willardi obscurus)|
|08/04/1978||43 FR 34476 34480||Listing of the New Mexican Ridge-nosed Rattlesnake as a Threatened Species with Critical Habitat|
|04/23/2007||72 FR 20134 20136||5-Year Reviews of 24 Southwestern Species|
|Date||Title||Plan Action Status||Plan Status|
|03/22/1985||New Mexico Ridge-nosed Rattlesnake||View Implementation Progress||Final|
|Date||Citation Page||Title||Document Type|
|04/23/2007||72 FR 20134 20136||5-Year Reviews of 24 Southwestern Species||
» Critical Habitat
|Date||Citation Page||Title||Document Type||Status|
|08/04/1978||43 FR 34476 34480||Listing of the New Mexican Ridge-nosed Rattlesnake as a Threatened Species with Critical Habitat||Final Rule||Final designated|
|05/26/1977||42 FR 27007 27009||Proposed Endangered Status and Critical Habitat for New Mexico Ridge-Nosed Rattlesnake; 42 FR 27007 27009 (Crotalus willardi obscurus)||Proposed Rule||Not Required|
To learn more about critical habitat please see http://ecos.fws.gov/crithab
» Conservation Plans
|HCP Plan Summaries|
» Life History
This is a montane woodland species found in Madrean evergreen woodland and Petran montane conifer forests, using the bottoms of steep, rocky canyons with intermittant streams or talus slopes. Elevations range from 5,000 to 8,500 feet, with lower elevation habitats being more arid and less well vegetated. Rock shelters and perennial bunch grasses are used as cover, with rocks, leaf litter, and downed logs also used for concealment. Winter dens (hibernacula) are often in talus slopes or other rocky areas with crevices and holes that protect the snakes from frost.
Adults mostly prey on small mammals, spiny lizards, and passarine birds. Juveniles mostly prey on spiny lizards and centipedes. The species is active during the day, and may use caudal or facial lures to attract prey. The juveniles have either black or yellow tail-tips, a feature that may assist in prey luring.
Movement / Home Range
Rattlesnakes are active on the surface as early as April and as late as October, with heightened activity between July and September. Temperature and rainfall (summer monsoons) are important factors in activity levels. This species moves only relatively short distances, and moves less frequently compared to other rattlesnake species. This sedentary nature contributes to the limited area known to be occupied by the species.
Adults reach sexual maturity when 80 percent full grown. Individuals reproduce biennially, with a gestation period of 13 months. Females mate in summer to fall with ovulation and fertilization occurring the early the following spring. The female carries the young in her oviducts until they are born alive in late July through August. Mean litter size for 12 broods was 5.5 young. There is no maternal care, and the young disperse from the natal area within a few days of their birth
Loss of habitat due to wildfire, improperly conducted prescribed fire, livestock grazing, and other land management actions that contribute to degraded watersheds have adverse effects to the rattlesnake. Human activity is also a threat, in part from illegal collection, but also from contacts between humans and snakes in the wild. The small size and limited habitat areas occupied by the extant populations increases the risks of extirpation due to loss of habitat or loss of individuals that come into contact with people.
» Other Resources
NatureServe Explorer Species Reports -- NatureServe Explorer is a source for authoritative conservation information on more than 50,000 plants, animals and ecological communtities of the U.S and Canada. NatureServe Explorer provides in-depth information on rare and endangered species, but includes common plants and animals too. NatureServe Explorer is a product of NatureServe in collaboration with the Natural Heritage Network.
ITIS Reports -- ITIS (the Integrated Taxonomic Information System) is a source for authoritative taxonomic information on plants, animals, fungi, and microbes of North America and the world.
FWS Digital Media Library -- The U.S. Fish and Wildlife Service's National Digital Library is a searchable collection of selected images, historical artifacts, audio clips, publications, and video.