Crotalus willardi

Meek, 1905

Ridge-nosed Rattlesnake

G5Secure Found in 1 roadless area NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
PSESA Status
MediumThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.102294
Element CodeARADE02130
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassReptilia
OrderSquamata
FamilyViperidae
GenusCrotalus
USESAPS
Other Common Names
Ridegenose Rattlesnake (EN)
Concept Reference
Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
Taxonomic Comments
Barker (2016) recommended elevating the five subspecies of C. willardi to species, which Crother (2017) do not follow until data are available for evaluation.

The traditional view of rattlesnake taxonomy that recognizes the two monophyletic sister genera Crotalus and Sistrurus (e.g. Brattstrom 1964) has recently been challenged. Stille (1987) and McCranie (1988) presented data that suggested Sistrurus is not monophyletic and rendered Crotalus paraphyletic. Parkinson (1999) found Sistrurus monophyletic but its position rendered Crotalus paraphyletic. Knight et al. (1993) used mtDNA to defend the traditional generic taxonomy, but in order to do so ignored the most parsimonious tree. The genus Crotalus is monophyletic when including the Mexican C. ravus (Murphy et al. 2002), and is supported as such in most recent phylogenies, as well as being the sister taxon to a monophyletic Sistrurus (e.g., Pyron et al. 2013) (Crother 2017).

See Campbell et al. (1989) for record of apparent hybridization with C. lepidus in southwestern New Mexico.
Conservation Status
Review Date2006-08-29
Change Date1996-10-31
Edition Date2006-08-29
Edition AuthorsHammerson, G.
Threat ImpactMedium
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences21 - 300
Range Extent Comments
The 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 1,460-2,750 meters (4,790-9,020 feet) (Campbell and Lamar 2004).

Subspecies obscurus occurs locally in the Animas Mountains (New Mexico), Peloncillo Mountains (Arizona and New Mexico), and Sierra de San Luis (Sonora and Chihuahua, Mexico) (Campbell et al. 1989, Holycross and Smith 1997, Campbell and Lamar 2004).

Subspecies willardi occurs in the Huachuca, Patagonia, Santa Rita, and Whetstone mountains of Arizona and southward into the Sierra de los Ojos, Sierra de Cananea, and Sierra Azul in north-central Sonora (Thirkhill and Starrett, 1992, Herpetol. Rev. 23:124; Campbell and Lamar 2004).
Occurrences Comments
This species is represented by a fairly large number of occurrences (subpopulations). On a range-wide scale, Campbell and Lamar (2004) mapped about 43 collection sites.
Threat Impact Comments
On a range-wide basis, no major threats are known. As of the early 1980s, populations in Arizona were not threatened (Johnson, cited by Ernst 1992). Threats in Arizona include illegal collecting, mining, recreational development, and wood cutting (Lowe et al. 1986).
Ecology & Habitat

Habitat

Habitat includes montane areas of pine-oak, oak scrub, oak-juniper, and pine-fir woodland, foothill canyons in pinyon-juniper woodland, and relatively humid canyon bottoms with canopies of sycamore, alder, box elder, and maple, often along stream courses, in areas with rock outcrops or talus, or among downed logs (Lowe et al. 1986, Ernst 1992, Degenhardt et al. 1996, Ernst and Ernst 2003, Stebbins 2003, Campbell and Lamar 2004). At the southern end of the range, habitats include pine-covered plateaus with scattered open meadows, hillsides with scattered pines, oaks, madrones, and rocks, and brushy hilltops (Armstrong and Murphy 1979). This snake is basically terrestrial buy may climb into low vegetation (Rossi and Feldner, 1993, Herpetol. Rev. 24:35). It seeks cover in crevices, among or under rocks, wood, or other debris, in old stumps, or in similar sites.

Ecology

Distance per move in New Mexico averaged less than 27 m, and daily activity areas averaged less than 225 sq m, but annual home range size was not reported (Smith et al. 2001).

Reproduction

Northern part of range: copulates in midsummer to early fall; ovulation and fertilization occur probably in early spring; bears 2-9 young, late July through August; adult females typically produce young at intervals of two years or more (Holycross and Goldberg 2001).
Terrestrial Habitats
Woodland - HardwoodWoodland - ConiferWoodland - MixedBare rock/talus/scree
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN2
ProvinceRankNative
New MexicoS1Yes
ArizonaS2Yes
Roadless Areas (1)
New Mexico (1)
AreaForestAcres
Peloncillo (NM)Coronado National Forest43,339
References (25)
  1. Armstrong, B. L., and J. B. Murphy. 1979. The natural history of Mexican rattlesnakes. Univ. Kansas Museum Natural History Special Publication. No. 5. vii + 88 pp.
  2. Barker, D.G. 2016. Ridgenose Rattlesnake, <i>Crotalus willardi</i> (Meek 1906). Pages 655-699 in G.W. Schuett, M.J. Feldner, C.F. Smith, and R.S. Reiserer (eds). 2016. Rattlesnakes of Arizona, Volume 1. ECO Herpetological Publishing, Rodeo, NM.
  3. Behler, J. L., and F. W. King. 1979. The Audubon Society field guide to North American reptiles and amphibians. Alfred A. Knopf, New York. 719 pp.
  4. Brattstrom, B. H. 1964. Evolution of the pit vipers. Transactions of the San Diego Society of Natural History 13(11):185-268.
  5. Campbell, et al. 1989. An apparent natural hybrid rattlesnake and <i>Crotalus willardi</i> (Viperidae) from the Peloncillo Mountains of southwestern New Mexico. Herpetologica 45:344-349.
  6. Campbell, J. A., and E. D. Brodie, Jr., editors. 1992. Biology of the pit vipers. Selva, Tyler, Texas.
  7. Campbell, J. A., and W. W. Lamar. 1989. The venomous reptiles of Latin America. Comstock Publ. Associates, Division of Cornell Univ. Press, Ithaca, New York. xii + 425 pp.
  8. Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
  9. Crother, B. I. (editor). 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 7th edition. SSAR Herpetological Circular 39:1-92.
  10. Crother, B. I. (editor). 2017. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 8th edition. SSAR Herpetological Circular 43:1-104. [Updates in SSAR North American Species Names Database at: https://ssarherps.org/cndb]
  11. Ernst, C. H. 1992. Venomous reptiles of North America. Smithsonian Institution Press, Washington, D.C. ix + 236 pp.
  12. Gloyd, H. 1940. The rattlesnakes. Chicago Academy Science, Special Publication No. 4.
  13. Holycross, A. T., and S. R. Goldberg. 2001. Reproduction in northern populations of the ridgenose rattlesnake, <i>Crotalus willardi</i> (Serpentes: Viperidae). Copeia 2001:473-481.
  14. Klauber, L. M. 1972. Rattlesnakes: their habits, life histories, and influence on mankind. Second edition. Two volumes. Univ. California Press, Berkeley.
  15. Knight, A., D. Styer, S. Pelikan, J. A. Campbell, L. D. Densmore III, and D. P. Mindell. 1993. Choosing among hypotheses of rattlesnake phylogeny: a best-fit rate test for DNA sequence data. Systematic Biology 42(3):356-367.
  16. Lowe, C. H., C. R. Schwalbe, and T. B. Johnson. 1986. The venomous reptiles of Arizona. Arizona Game and Fish Department. ix + 115 pp.
  17. McCranie, J. R. 1988. Description of the hemipenis of <i>Sistrurus ravus </i>(Serpentes: Viperidae). Herpetologica 44:123-126.
  18. Murphy, R. W., J. Fu, and A. Lathrop. 2002. Phylogeny of the rattlesnakes (<i>Crotalus </i>and <i>Sistrurus</i>) inferred from sequences of five mitochondrial DNA genes. Pages 69-92 in G. W. Schuett, M. Hoggren, M. E. Douglas, and H. W. Greene, editors. Biology of the Vipers. Eagle Mountain Publishing, Eagle Mountain, Utah.
  19. Parkinson, C. L. 1999. Molecular systematics and biogeographical history of pitvipers as determined by mitochondrial ribosomal DNA sequences. Copeia 1999:576-586.
  20. Pyron, R. A., F. T. Burbrink, and J. J. Wiens. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evolutionary Biology 29:131.
  21. Smith, L. J., A. T. Holycross, C. W. Painter, and M. E. Douglas. 2001. Montane rattlesnakes and prescribed fire. Southwestern Naturalist 46:54-61.
  22. Stebbins, R. C. 1985a. A field guide to western reptiles and amphibians. Second edition. Houghton Mifflin Company, Boston, Massachusetts. xiv + 336 pp.
  23. Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. Third edition. Houghton Mifflin Company, Boston.
  24. Stille, B. 1987. Dorsal scale microdermatoglyphics and rattlesnake (<i>Crotalus </i>and <i>Sistrurus</i>) phylogeny (Reptilia: Viperidae: Crotalinae). Herpetologica:98-104.
  25. U.S. Fish and Wildlife Service (USFWS). 1990. Endangered and threatened species recovery program: report to Congress. 406 pp.