:''Common names: ridge-nosed rattlesnake, Willard's rattlesnake, Willard's rattler Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates. 1,105 pp. (in 2 volumes). (7th printing, 1985, ). (''Crotalus willardi'', pp. 1034-1037, Figures 294-295 + Map 67 on p. 951).'' ''Crotalus willardi'' is a

venomous Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

pit viper The Crotalinae, commonly known as pit vipers,Mehrtens JM (1987). ''Living Snakes of the World in Color''. New York: Sterling Publishers. 480 pp. . or pit adders, are a subfamily (biology), subfamily of Viperidae, vipers found in Asia and the ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

found in the southwestern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. This snake is found mainly in the "sky island" region. The IUCN reports this snake's conservation status as being of Least Concern. It is the official state reptile of

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

Etymology

The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''willardi'', is in honor of its discoverer, "Professor" Frank Cottle Willard, a businessman from Tombstone, Arizona.

Taxonomy

Originally described in 1905, ''Crotalus willardi'' is the most recent rattlesnake species to be discovered in the United States. Five

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

are currently recognized, including the

nominate subspecies In biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. ...

, ''Crotalus willardi willardi'', described here. ''C. w. willardi'' is commonly known as the Arizona ridge-nosed rattlesnake, and is the

state reptile Twenty-eight U.S. states have named an official state reptile. As with other United States state symbols, state symbols, states compare admirable aspects of the reptile and of the state, within designating statutes. Schoolchildren often start c ...

Description

''Crotalus willardi'' is a rather small rattlesnake with all

measuring one to two feet (30–60 cm) in length. Color patterns are generally a dark brown base with pale or white horizontal striping, but vary slightly among subspecies. It has the odd distinction of being named last as a new species, as there is no mistaking the clear cut ridge that follows the countour of its snout, a ridge formed by turning up the scales on the end of its nose.

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.

Conservation status

The species ''C. willardi'' is classified as Least Concern on the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

Red List of Threatened Species The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological spe ...

(v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2007. Although four of the five

are secure, the New Mexico ridge-nosed rattlesnake (''C. w. obscurus'') is an endangered subspecies and listed as

threatened A threatened species is any species (including animals, plants and fungi) which is vulnerable to extinction in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensatio ...

by the

US Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is a U.S. federal government agency within the United States Department of the Interior which oversees the management of fish, wildlife, and natural habitats in the United States. ...

. Remaining populations are scattered throughout

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

and the northern part of Mexico.

Habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

is the cause of declining numbers, but critical habitat designations (recovery measures) have been proposed.

Behavior and diet

Rattlesnakes are primarily ambush hunters; they coil and lie waiting for prey to approach within striking distance. The diet of ''C. willardi'' includes small

mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

lizards Lizard is the common name used for all squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The ...

birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

, and large

centipedes Centipedes (from Neo-Latin , "hundred", and Latin language, Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphyl ...

. The young feed primarily on large

(''Scolopendra'' spp.) and lizards, whereas adults feed primarily on mammals and birds.

Reproduction

Like other rattlesnakes, ''C. willardi'' is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

, meaning it gives birth and does not lay eggs. Contrasting with

viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...

animals, the young still develop within an egg inside the female snake until their time of birth.

Copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...

occurs from late summer to early fall, and

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

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 400 mm (16 in) in body (snout to vent) length. Although captive snakes have reproduced annually, wild females probably reproduce every second or third year.Holycross & Goldberg, 2001.

Venom

Due to the generally small size of ''C. willardi'', venom discharge yields are low; thus, the largely

hemotoxic Haemotoxins, hemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''haemotoxin'' is to some degree a misnomer since toxins that damage ...

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 Biting is an action involving a set of teeth closing down on an object. It is a common zoological behavior, being found in toothed animals such as mammals, reptiles, amphibians, fishes, and arthropods. Biting is also an action humans participate ...

Subspecies

References

External links

*
Taxonomy of the New Mexican Ridge-nosed Rattlesnake
a
Virginia Tech
Accessed 12 December 2007.

a
Biopark
Accessed 12 December 2007.
US Fish & Wildlife Service Species Profile: ''Crotalus willardi''
a
U.S. Fish & Wildlife Service
Accessed 12 December 2007. {{Taxonbar, from=Q1517877 willardi Symbols of Arizona Reptiles described in 1905 Fauna of the Sierra Madre Occidental