Crotalus willardi is a venomous pit viper species found in the southwestern United States and Mexico. 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.
The specific name, willardi, is in honor of its discoverer, "Professor" Frank Cottle Willard, a businessman from Tombstone, Arizona.
Originally described in 1905, Crotalus willardi is the most recent rattlesnake species to be discovered in the United States. Five subspecies are currently recognized, including the nominate subspecies, Crotalus willardi willardi, described here.C. w. willardi is commonly known as the Arizona ridge-nosed rattlesnake, and is the state reptile of Arizona.
Crotalus willardi is a rather small rattlesnake with all subspecies 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. The distinctive ridges along each side of its nose, which are a series of upturned scales, are unique to this species and are the origin of one of its common names, ridge-nosed rattlesnake.
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.
The species C. willardi is classified as Least Concern on the IUCN Red List of Threatened Species (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 subspecies are secure, the New Mexico ridge-nosed rattlesnake (C. w. obscurus) is an endangered subspecies and listed as threatened by the US Fish and Wildlife Service. Remaining populations are scattered throughout New Mexico, Arizona and the northern part of Mexico. Habitat destruction is the cause of declining numbers, but critical habitat designations (recovery measures) have been proposed.
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, lizards, birds, and large centipedes. The young feed primarily on large centipedes (Scolopendra spp.) 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 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 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.
Due to the generally small size of C. willardi, venom discharge yields are low; thus, the largely hemotoxic 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.
|Subspecies||Taxon author||Common name||Geographic range|
|C. w. amabilis||Anderson, 1962||Del Nido ridge-nosed rattlesnake||Mexico in north-central Chihuahua|
|C. w. meridionalis||Klauber, 1949||Southern ridge-nosed rattlesnake||Mexico in southern Durango and southwestern Zacatecas|
|C. w. obscurus||Harris & Simmons, 1974||New Mexico ridge-nosed rattlesnake||The US in extreme southeastern Arizona and extreme southwestern New Mexico, Mexico in extreme northwestern Chihuahua and extreme northeastern Sonora|
|C. w. silus||Klauber, 1949||Chihuahuan ridge-nosed rattlesnake||Western Chihuahua and eastern Sonora|
|C. w. willardi||Meek, 1905||Arizona ridge-nosed rattlesnake||Southeastern Arizona, and northern Sonora|
Crotalus scutulatus is a highly venomous pit viper species found in the deserts of the southwestern United States and central Mexico. It is perhaps best known for its potent neurotoxic-hemotoxic venom, which is considered one of the world's most potent rattlesnake venom. Two subspecies are recognized, including the nominate subspecies described here.
The timber rattlesnake, canebrake rattlesnake or banded rattlesnake, is a species of venomous pit viper endemic to eastern North America. This is the only rattlesnake species in most of the populous northeastern United States and is second only to its cousins to the west, the prairie rattlesnake, as the most northerly distributed venomous snake in North America. No subspecies are currently recognized.
Crotalus molossus is a venomous pit viper species found in the southwestern United States and Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.
Crotalus lepidus is a venomous pit viper species found in the southwestern United States and northern central Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.
Crotalus basiliscus is a venomous pit viper species in the family Viperidae. The species is endemic to western Mexico. The specific name, basiliscus, is derived from the Greek word for king, βασιλισκος (basiliskos), and alludes to this snake's large size and potent venom. There are no subspecies which are recognized as being valid.
Crotalus ruber is a venomous pit viper species found in southwestern California in the United States and Baja California in Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.
Crotalus viridis is a venomous pit viper species native to the western United States, southwestern Canada, and northern Mexico. Currently, two subspecies are recognized, including the nominate subspecies described here.
Crotalus mitchellii is a venomous pit viper species in the family Viperidae. The species is endemic to the Southwestern United States and adjacent northern Mexico. The species was named in honor of Silas Weir Mitchell (1829–1914), an American medical doctor who also studied rattlesnake venoms. Five subspecies are currently recognized, including the nominate subspecies described here.
Crotalus ravus is a venomous pit viper species, found only in Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.
Crotalus viridis nuntius is a venomous pit viper subspecies native primarily to the desert plateau of the northeastern portion of the American state of Arizona, but also ranges into northwestern New Mexico. Named for the Native American Hopi tribe, which inhabits the region, its range overlaps that of the nominate subspecies and some interbreeding is believed to occur. The taxonomy of the C. viridis group is a matter of debate, many considering the various subspecies to be nothing more than locality variations.
Crotalus simus is a venomous pit viper species found in Mexico and Central America. The specific epithet is Latin for "flat-nosed", likely because its head is blunt compared with lanceheads (Bothrops). Three subspecies are recognized, including the nominate subspecies described here.
Crotalus oreganus is a venomous pit viper species found in North America in the western United States, and parts of British Columbia.
Crotalus atrox tortugensis is a venomous pit viper subspecies found only on Tortuga Island in the Gulf of California.
Crotalus aquilus is a venomous pit viper species found in the highlands of central Mexico. No subspecies is currently recognized. The specific name, aquilus, is Latin for "eagle" and refers to the high altitude at which this species is found.
Crotalus pricei is a species of venomous snake, a pit viper in the family Viperidae. The species is endemic to the southwestern United States and northern Mexico. Two subspecies are recognized, including the nominate subspecies described here.
The Mexican lance-headed rattlesnake or lance-headed rattlesnake is a venomous pit viper species found in central Mexico. No subspecies is currently recognized.
Crotalus stejnegeri is a venomous pit viper species found in western Mexico. No subspecies is currently recognized.
Crotalus willardi obscurus is a venomous pitviper subspecies found in northwestern Mexico and the southwestern United States.This is the only venomous snake listed as Threatened by the U.S. Fish and Wildlife Service.
Crotalus lorenzoensis is a species of pitviper, a venomous snake in the subfamily Crotalinae of the family Viperidae. The species is endemic to San Lorenzo Sur Island, Mexico.
Crotalus mitchellii muertensis is a venomous pitviper subspecies endemic to El Muerto Island, Mexico. It is sometimes treated as a full species, Crotalus muertensis.
|Wikimedia Commons has media related to Crotalus willardi .|