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Overview

Distribution

Range Description

This species is known from Ángel de la Guarda Island in the northern Gulf of California, México (Musser and Carleton 2005). It was historically also found on three nearby, smaller islands (i.e, Granito, Mejía, and Estanque).
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Ecology

Habitat

Gulf of California Xeric Scrub

This taxon occurs in the Gulf of California xeric scrub ecoregion, situated along the eastern coastal zone and Gulf of California versant of the Baja Peninsula in Mexico, and is delineated by the spine of the La Giganta Sierra Mountains. This ecoregion, located entirely within the nation of Mexico, is classified within the Deserts and Xeric Scrublands biome.  Species richness of plants is high in the ecoregion, but modest for fauna; however, endemism is high in this arid habitat, which receives some of the lowest precipitation in all of Mexico.

Dominant flora species are Creosote Bush (Larrea tridentata) and White Bursage (Ambrosia dumosa); moreover, other plant taxa occurring here include: Arizona Nettle-spurge (Jatropha cinerea), Desert Ironwood (Olneya tesota), Acacia brandegeana, Blue Palo Verde (Cercidium floridum), and Chloroleucon mangense var. leucospermum. Species of more mesic habitats occur on the many oases that are present on the Baja Peninsula: Mexican Fan Palm (Washingtonia robusta), Southern Cattail (Typha domingensis), Common Reed (Phragmites australis) and Date Palm (Phoenix dactylifera). The oases are remnants of more extensive mesic environments that existed in the peninsula in prehistoric times; these earlier habitats consisted of larger bodies of surface water distributed throughout the peninsula, surrounded by vegetation that belongs to wetlands interspersed with common elements of the xeric scrub.

The Isla Santa Catalina Leaf-toed Gecko (Phyllodactylus bugastrolepis) is an endemic reptile to the Gulf of California xeric scrub, occurring only on Isla Santa Catalina, and often found in dead cacti. Other reptile species found here include: the endemic Santa Catalina Island Whiptail (Cnemidophorus catalinensis), seen only on Santa Catalina Island in the Gulf of California; the endemic Santa Catalina Island Spiny Lizard (Sceloporus lineatulus); the endemic San Lorenzo Islands Lizard (Uta antiqua); the endemic Salsipuedes Island Whiptail (Cnemidophorus canus), restricted in occurrence to endemic to the islands of Salsipuedes, San Lorenzo Norte and San Lorenzo Sur ; the endemic Raza Island Leaf-toed Gecko (Phyllodactylus tinklei),  found on Raza Island; the endemic Santa Cruz Leaf-toed Gecko (Phyllodactylus santacruzensis); the endemic Isla Partida Del Norte Leaf-toed Gecko (Phyllodactylus partidus), found solely on Isla Partida Norte and Cardonosa Este, in the Gulf of California; the endemic Angel Island Leaf-toed Gecko (Phyllodactylus angelensis), found only on several Gulf of California islands in the county of Islas Angel de la Guarda; the endemic Las Animas Island Gecko (Phyllodactylus apricus); and the near-endemic Marbled Whiptail (Cnemidophorus marmoratus), the latter of which occupies burrows in sandy soils.

There are a number of mammalian taxa present in the Gulf of California xeric scrub, including: Angel Island Mouse (Peromyscus guardia CR), an ecoregion endemic known only from Ángel de la Guarda Island in the northern Gulf of California, México; the ecoregion endemic Burt's Deermouse (Peromyscus caniceps CR), known only from Montserrat Island, Baja California Sur, Mexico; Baja California Rock Squirrel (Spermophilus atricapillus EN), a Baja California endemic; and the Fish-eating Bat (Myotis vivesi VU), which is found along in the coastal zone of Baja California and Sonora. Bunker's Woodrat (Neotoma bunkeri EX) was previously endemic to the ecoregion and is now extinct.

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Habitat and Ecology

Habitat and Ecology
These islands are desert scrub.

Systems
  • Terrestrial
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
B2ab(iv,v)

Version
3.1

Year Assessed
2008

Assessor/s
Álvarez-Castañeda, S.T., Castro-Arellano, I., Lacher, T. & Vázquez, E.

Reviewer/s
McKnight, M. (Global Mammal Assessment Team) & Amori, G. (Small Nonvolant Mammal Red List Authority)

Contributor/s

Justification
Listed as Critically Endangered (Possibly Extinct) because there is no known location for the species at present, but the species may persist in small numbers on Ángel de la Guarda Island, and surveys are urgently needed to confirm this. Should the species be located, its area of occupancy will be very small; less than 10 km², in a single location, with a continuing decline in the number of mature individuals due to introduced predators and competitors. The species has likely been extirpated recently on the three other islands from which it was known.
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Population

Population
Although this species was apparently common in the mid-1960s, population declines have been observed over the past three decades to the extent that no population is currently known to be still extant, and the species could in fact be extinct. On Ángel de la Guarda Island, it was last recorded in 1991 (Mellink et al. 2002); populations are thought to be extremely low on this island due to predation by feral cats, and the species may possibly have been extirpated (Vázquez-Domínguez et al. 2004). No individuals have been recorded in several recent surveys on the Islands of Mejía and Granito (Álvarez-Castañeda and Ortega-Rubio 2003), and the species is likely extirpated from these islands (Mellink et al. 2002; Álvarez-Castañeda and Ortega-Rubio 2003). The species is said to be extirpated from Estanque Island (Vázquez-Domínguez et al. 2004).

Population Trend
Decreasing
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Threats

Major Threats
Major threats to this species include competition with introduced rodents, predation by feral or domestic cats, and intrinsic factors due to its small population size and limited distribution. There is a risk that more human activity will result from the Mexican government's plans to make the Gulf of California a major tourist destination, which will substantially increase the chances of detrimental introduction of non-native species (Álvarez-Castañeda et al. 2006).
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Management

Conservation Actions

Conservation Actions
This species' range occurs within the Islas del Golfo de California Biosphere Reserve. Surveys are urgently needed to determine whether populations of this species exist on Ángel de la Guarda Island (Vázquez-Domínguez et al. 2004). If populations are found they should be secured by controlling introduced competitors and predators, a captive breeding program should be instigated with the possibility of translocating individuals to Estanque Island where cats (or rather the single cat) was recently removed (Vázquez-Domínguez et al. 2004), and ways to mitigate possible increased human activity due to the Mexican government's plans to make the Gulf of California a major tourist destination should be explored (Álvarez-Castañeda et al. 2006).
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Wikipedia

Angel Island mouse

The Angel Island mouse or La Guarda deermouse (Peromyscus guardia) is a species of rodents in the family Cricetidae.[2] It is endemic to Mexico, where it is historically known only from the island of Ángel de la Guarda, and nearby islets. The species is believed to be extirpated from the three smaller islands, and may be extinct on Ángel de la Guarda, as well. The species is threatened by predation by feral cats, and by competition from introduced rodents.

Description[edit]

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 19 to 22 cm (7.5 to 8.7 in) in total length, including tails 9 to 12 cm (3.5 to 4.7 in) long. Females have four abdominal teats.[3]

Distribution and habitat[edit]

The Angel Island mouse is endemic to Ángel de la Guarda Island, a mountainous 359 sq mi (930 km2) island off the east coast of Baja California Sur, 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.[3]

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[edit]

The Angel Island mouse is believed to be descended from an isolated population of cactus mice,[4] possibly belonging to the P. e. fraterculus species or subspecies[5] 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.[6] The two species remain able to interbreed, although it is not known whether the resulting hybrids are fertile.[3] Little is known of the behaviour or detailed biology of the species, although it is believed to breed in the spring.[3]

Conservation status[edit]

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.[7] 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 and black rats, which compete with the endemic species for resources.[1][3] The subspecies resident on the two northern islets are now listed as extinct,[8] while the entire population on the southern islet of Estanque was probably driven to extinction by a single cat, present on the island only between 1998 and 1999.[9]

The species is currently listed as critically endangered by the IUCN, but since no living specimens have been seen for 20 years, as of 2011, it may well be entirely extinct. If the species still survives, it is likely restricted to an area of no more than 10 km2 (3.9 sq mi).[1]

References[edit]

  1. ^ a b c Álvarez-Castañeda, S.T., Castro-Arellano, I., Lacher, T. & Vázquez, E. (2008). "Peromyscus guardia". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature. Retrieved 5 March 2011. 
  2. ^ Musser, G. G.; Carleton, M. D. (2005). "Superfamily Muroidea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 1068. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  3. ^ a b c d e Rios, E. & Álvarez-Castañeda, S.T. (2011). "Peromyscus guardia (Rodentia: Cricetidae)". Mammalian Species 43 (1): 172–176. doi:10.1644/885.1. 
  4. ^ Lawlor, T.E. (1971). "Evolution of Peromyscus on northern islands in the Gulf of California, Mexico". Transactions of the San Diego Society of Natural History 16 (5): 91–124. 
  5. ^ Riddle, B.R. et al. (2000). "Phylogeography and systematics of the Peromyscus eremicus species group and the historical biogeography of the North American warm regional deserts". Molecular Phylogenetics and Evolution 17 (2): 145–160. doi:10.1006/mpev.2000.0841. 
  6. ^ Avise, J.C. et al. (1974). "Biochemical polymorphism and systematics in the genus Peromyscus: V. Insular and mainland species of the subgenus Haplomylomys". Systematic Zoology 23 (2): 226–238. doi:10.2307/2412134. 
  7. ^ Banks, R.C. (1967). "The Peromyscus guardia–interparietalis complex". Journal of Mammalogy 48 (2): 210–218. JSTOR 1378023. 
  8. ^ Álvarez-Castañeda, S.T. & Ortega-Rubio, A. (2003). "Current status of rodents on islands in the Gulf of California". Biological Conservation 109 (2): 157–163. doi:10.1016/S0006-3207(02)00121-0. 
  9. ^ Vázquez-Domínguez, E. et al. (2004). "Extirpation of an insular subspecies by a single introduced cat: the case of the endemic deer mouse, Peromyscus guardia on Estanque Island, Mexico". Oryx 38 (3): 347–350. doi:10.1017/S0030605304000602. 
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