Common names: Tancitaran dusky rattlesnake.

Crotalus pusillus 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 west-central 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

Adult males may grow to more than 50 cm in length. Females are smaller. The largest recorded length for a specimen is 68.2 cm.

Behavior

Campbell and Lamar (2004) stated that they found this species only to be active during the day. Within its range, nighttime temperatures are low and apparently restrict its activity.

Geographic range

Found in west-central 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 Sierra de Coalcomán of southwestern Michoacán

Michoacán

Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...

, the Transverse Volcanic Cordillera of west-central Michoacán, and in adjacent Jalisco

Jalisco

Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...

. It is probably also found in northeastern Colima

Colima

Colima is one of the 31 states which, with the Federal District, make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima....

. The type locality given is "Tancítaro, Michoacán, Mexico, altitude 5,000 ft." (5,000 ft. = 3,000 m). Occurs at elevations between 1,525 m and 2,380 m.

Conservation status

This species is classified as Endangered (EN) 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 5000 km², estimates indicate that its range is severely fragmented or known to exist at no more than five locations, and that a continuing decline has been, observed, inferred or projected in the area, extent and/or quality of its habitat. Therefore it is considered to be facing a very high risk of extinction in the wild. The population trend is unknown. Year assessed: 2007.