The Santa Cruz mouse (''Peromyscus sejugis'') is a species of

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

in the family

Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At almost 608 species, it is the second-largest family of mammals, and h ...

. It is endemic to

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, where it is found only on two small islands in the southern

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

. Feral cats on

Santa Cruz Island Santa Cruz Island ( Spanish: ''Isla Santa Cruz'', Chumash: ''Limuw'') is located off the southwestern coast of Ventura, California, United States. It is the largest island in California and largest of the eight islands in the Channel Islands ...

are a threat.

Description

The Santa Cruz mouse is a relatively large member of its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

, measuring in total length, including a tail long, and weighing an average of . The fur on the upper parts of the body is a dull greyish color, with a yellow-brown face, and sometimes a yellowish line along the flanks. The underparts are white, and the tail is distinctly darker on its upper surface than on its lower. It is generally similar in appearance to the North American deermouse, but is larger, with a longer snout and a duller color.

Distribution and habitat

The mouse is found only on

and the neighboring islet of

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...

, both of which lie in the south-western

, about from the mainland. The larger island, with an area of , is rocky and rugged, with the dominant vegetation including elephant trees, clustervines, and nettlespurge. Mice have been collected from the bottoms of ravines on the island, rather than on the hilltops. San Diego Island, with an area of just , is little more than a single rocky mound with some ground vegetation and cacti. Santa Cruz mice are the only native mammals known to live on the islands.

References

Peromyscus Endemic mammals of Mexico Endemic fauna of the Baja California Peninsula Rodents of North America Fauna of Gulf of California islands Endangered biota of Mexico Endangered fauna of North America Mammals described in 1932 Taxonomy articles created by Polbot {{Peromyscus-stub