Common names: Long-tailed rattlesnake.

Crotalus stejnegeri is a venomous

Venomous snake

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...

 pitviper

Crotalinae

The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 found in western Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. No subspecies are currently recognized.

Description

Adults do not usually grow to more than 60 cm in length. The greatest length recorded for a specimen is 72.4 cm. The tail is relatively long, representing 11-14.8% of the total length of adult male snakes and 9.8-12.5% in females. Klauber (1940) suggested that, since the rattle is tiny, it is probably not audible. A very rare species known only from approximately twelve specimens.

Geographic range

Found in western Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 in the mountains and foothills of eastern Sinaloa

Sinaloa

Sinaloa officially Estado Libre y Soberano de Sinaloa is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 18 municipalities and its capital city is Culiacán Rosales....

, western Durango

Durango

Durango officially Estado Libre y Soberano de Durango is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. The state is located in Northwest Mexico. With a population of 1,632,934, it has Mexico's second-lowest population density, after Baja...

 and probably northern Nayarit

Nayarit

Nayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico...

, between 500 m and 1,200 m altitude. The type locality given is "Plumosas [Plomosas], Sinaloa, Mexico."

Conservation status

This species is classified as Vulnerable (VU) on the IUCN

World Conservation Union

The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...

 Red List of Threatened Species

IUCN Red List

The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

with the following criteria: B1ab(iii) (v3.1, 2001). A species is listed as such when the best available evidence indicates that its extent of occurrence is estimated to be less than 20,000 km², estimates indicate that it is severely fragmented or known to exist at no more than 10 locations, and a continuing decline has been observed, inferred or projected in its area, extent and/or quality of habitat. Therefore, it is considered to be facing a high risk of extinction in the wild. The population trend is down. Year assessed: 2007.