The Angel Island mouse (''Peromyscus guardia''), or La Guarda deermouse, 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 na ...
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 has m ...
.
Distribution
It is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to Mexico, where it is historically known only from the island of
Ángel de la Guarda and nearby islets in the northwestern
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 Ca ...
,
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
.
The species is believed to be
extirpated
Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
from the three smaller islands, and may be
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
on Ángel de la Guarda, as well. The species is threatened by predation by
feral cat
A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact: it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...
s, and by competition from introduced rodents.
Description
The Angel Island mouse has pale grey-brown fur with white underparts and feet, and large, hairless ears. It is most readily distinguished from closely related species on the mainland by subtle characteristics of the skull, or through genetic or biochemical analysis. Adults range from in total length, including tails long. Females have four abdominal teats.
Distribution and habitat
The Angel Island mouse is endemic to Ángel de la Guarda Island, a mountainous island off the east coast of
Baja California Sur
Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...
, and to three much smaller islands in the same group. Within the islands, the species appears to be confined to sandy beaches, and perhaps to rockier areas nearby, and has not been found in the high mountainous terrain that forms most of their land area.
[
Three subspecies are formally recognised, although two of these are now extinct:
* ''P. g. guardia'' - Ángel de la Guarda, Estanque
* † ''P. g. harbisoni'' - Isla Granito
* † ''P. g. mejiae'' - Mejia
]
Biology
The Angel Island mouse is believed to be descended from an isolated population of cactus mice, possibly belonging to the ''P. e. fraterculus'' species or subspecies The critically endangered San Lorenzo mouse, which inhabits a smaller group of islands to the south, may be descended from the same stock, isolated when the islands separated from the mainland as sea levels rose at the end of the last ice age. The two species remain able to interbreed, although it is not known whether the resulting hybrids are fertile.[ Little is known of the behaviour or detailed biology of the species, although it is believed to breed in the spring.][
]
Conservation status
As recently as the 1960s, the Angel Island mouse was reported to be abundant on at least three of the four islands it was known to inhabit. However, no specimens have been found on the islands since 1991, despite a number of surveys. The main risks to the species come from feral cats, and from introduced house mice
The house mouse (''Mus musculus'') is a small mammal of the order Rodentia, characteristically having a pointed snout, large rounded ears, and a long and almost hairless tail. It is one of the most abundant species of the genus '' Mus''. Althoug ...
and black rat
The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
s, which compete with the endemic species for resources.[ The subspecies resident on the two northern islets are now listed as ]extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
, while the entire population on the southern islet of Estanque was probably driven to extinction by a single cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
, present on the island only between 1998 and 1999.
The house mouse
The house mouse (''Mus musculus'') is a small mammal of the order Rodentia, characteristically having a pointed snout, large rounded ears, and a long and almost hairless tail. It is one of the most abundant species of the genus '' Mus''. Althoug ...
now occupies the habitat and the trophic niche that the Angel Island mouse occupied when it was abundant. This replacement of species in a habitat enhances the biotic homogenization of species. The species is currently listed as critically endangered by the IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
, but since no living specimens have been seen for 20 years, , it may well be entirely extinct. If the species still survives, it is likely restricted to an area of no more than .
References
{{Taxonbar, from=Q1769295
Peromyscus
Endemic mammals of Mexico
Fauna of Gulf of California islands
Endemic fauna of the Baja California Peninsula
Rodents of North America
Natural history of Baja California
Mammals described in 1912
Taxa named by John Kirk Townsend
Critically endangered fauna of North America
Taxonomy articles created by Polbot