Mojave ground squirrel
| Mojave ground squirrel | ||||||||||||
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Mojave ground squirrel ( Xerospermophilus mohavensis ), graphic from Natural History of the Ground Squirrels of California , 1918 |
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| Xerospermophilus mohavensis | ||||||||||||
| ( Merriam , 1889) |
The Mojave ground squirrel ( Xerospermophilus mohavensis , syn .: Spermophilus mohavensis ) is a species of squirrel from the genus Xerospermophilus . He lives exclusively in the northwest Mojave Desert and the Owens Valley in southern California .
features
The Mojave ground squirrel reaches a head-torso length of about 21.0 to 23.0 centimeters and weighs 70 to 300 grams. The tail is about 57 to 72 millimeters long and is thus significantly shorter than the rest of the body. A sexual dimorphism does not occur, the females and males differ neither in size nor in color. The back coloring of the animals is monochrome light brown to gray brown without a pattern or dots. They often have a cinnamon-colored wash in the head area. The belly is white to creamy white, the feet are pale sand-colored to cinnamon-colored. The tail is broad and very short. The top of the tail is reddish-brown, the underside white to creamy white, and the entire tail is frosted whitish.
Within the entire distribution area, besides the Mojave ground squirrel, only the white-tailed antelope ground squirrel ( Ammospermophilus leucurus ) occurs, which, however, differs significantly from the Mojave ground squirrel due to the striking stripe color. Adjacent and overlapping in narrow areas is the distribution area of the closely related round-tailed squirrel ( Xerospermophilus tereticaudus ). The main distinguishing feature compared to this is the shorter and wider tail with the white underside, which is sandy brown in the round-tailed ground squirrel. In addition, the claws are shorter and more blunt and the cheeks are brownish instead of whitish. The distribution area of the California ground squirrel ( Otospermophilus beecheyi ) is also overlapping , but it is significantly larger than the Mojave ground squirrel and the round-tailed ground squirrel and has a spotted fur.
distribution
The Mojave ground squirrel is endemic to southern California in the northwest Mojave Desert and Owens Valley . It occurs spotty in this slightly cooler area of the desert, depending on the available vegetation and the climate. The individual distribution areas are in southwestern Inyo County , eastern Kern County , the extreme northeastern part of Los Angeles County and northwestern San Bernardino County , from Olancha in Inyo County to Victorville in San Bernardino County and from the Tehachapi Mountains in Kern County to the Granite Mountains in San Bernardino County. The southern limit of distribution is the Mojave River , but historically the species also occurred east of the river in the Lucerne Valley. The altitude distribution ranges from 610 to 1800 meters.
Way of life
The Mojave ground squirrel is diurnal and lives in dry desert areas with sufficient vegetation on sandy to gravelly crumbly soils. Stocks of creosote bushes ( Larrea tridentata ) and the corresponding associated plants are preferred. They are omnivorous and the diet consists primarily of parts of vegetation such as leaves, flowers and sprouts as well as available seeds from grasses, herbs, bushes, cacti and yuccas . In addition, there are comparatively large amounts of insects and other animal foods. The food is collected in the cheek pouches and is usually eaten on a slightly more prominent stone as an observation post.
The animals live like other ground squirrels on the ground and in underground burrows. These are usually located on the edge of the districts at a distance of up to 250 meters from the center and individual animals inhabit several burrows that they use as hiding places, for rearing young and for wintering. In the evening, the overnight accommodation is locked to prevent predators from entering. The activity of the animals ranges from spring, usually February or March, to summer in August. From August to spring the animals overwinter in their burrows and live on their fat reserves during this time. The males usually wake up and leave their burrows about two weeks before the females. Then they start to define territories. Outside of the mating season, the animals are loners and they defend their territories by aggressively chasing away intruders. The territories of the male animals are significantly larger than those of the female, on average males use 6.74 ha and females 0.73 ha.
The mating season begins immediately after the females wake up in the burrows in February to March. After a gestation period of 29 to 30 days, the females give birth to a litter of four to nine young in late March to April. In years with very severe drought, no offspring are born, and the animals can also disappear completely in certain regions. After the young animals leave the nest, they look for their own territory and can move up to more than six kilometers from the brood nest. The average distance for males is 1.5, for females 0.5 kilometers from the brood burrow.
The most important predators for the Mojave brick are birds of prey, snakes, silver badgers ( Taxidea taxus ), coyotes ( Canis latrans ) and bobcats ( Lynx rufus ). The animals are not shy of people and when threatened they usually do not flee, but rather push themselves to the ground and rely on their camouflage. Your alarm calls consist of a loud and high-pitched harsh beep.
Systematics
The Mojave ground squirrel is classified as a separate species within the genus Xerospermophilus , which consists of four species. The species has long been classified as part of the ground squirrel and within the subgenus Xerospermophilus , but after a comprehensive molecular biological investigation, this was considered as an independent genus together with several other genera. The first scientific description comes from the American zoologist Clinton Hart Merriam from 1889. He described the species as Spermophilus mohavensis on the basis of nine individuals from the region on the Mojave River , later this was narrowed to Rabbit Springs east of the city of Hesperia in San Bernardino County .
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Phylogenetic system of the genus Xerospermophilus according to Fernández 2012
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The Mojave ground squirrel is closely related to the round-tailed ground squirrel, with the distribution areas overlapping in a narrow strip. In this zone it is in the areas of Helendale and the Coyote Dry Lake to hybridization between the two species. In a phylogenetic study with a focus on the relationship of the Perote ground squirrel ( Xerospermophilus perotensis ), the Mojave ground squirrel and the round-tailed ground squirrel were identified as sister species and compared to the other two species of the genus Xerospermophilus . Apart from the nominate form, no subspecies are distinguished within the species .
Status, threat and protection
The Mojave ground squirrel is classified as endangered (vulnerable) by the International Union for Conservation of Nature and Natural Resources (IUCN), but no concrete population figures are available. This is justified by the limited distribution area with an area of less than 20,000 km 2 as well as the strong fragmentation by human settlements and roads and the qualitative deterioration of the habitats for the squirrels.
The populations are also subject to strong fluctuations, partly as a result of extreme drought, which prevents the animals from reproducing in a few years. In this case, regionally populations can disappear completely and a new colonization of these regions takes place in the following years coming from the neighboring areas. For this reason above all, a wide distribution of the offspring is necessary.
supporting documents
- ↑ a b c d e f g h i j k l m Richard W. Thorington Jr. , John L. Koprowski, Michael A. Steele: Squirrels of the World. Johns Hopkins University Press, Baltimore MD 2012, ISBN 978-1-4214-0469-1 , pp. 292-293 .
- ↑ a b c Troy L. Best : Spermophilus mohavensis. Mammalian Species 509, 1995; Pp. 1-7. ( Full text )
- ↑ a b c d e f Xerospermophilus mohavensis in the IUCN Red List of Threatened Species 2015.4. Posted by: DJ Hafner & NatureServe (G. Hammerson, DF Williams), 2008. Retrieved April 19, 2016.
- ↑ Matthew D. Herron, Todd A. Castoe, Christopher L. Parkinson: Sciurid phylogeny and the paraphyly of holarctic ground squirrels (Spermophilus). Molecular Phylogenetics and Evolution 31, 2004; Pp. 1015-1030. ( Full text ( Memento of the original from April 17, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. , PMID 15120398 )
- ↑ Kristofer M. Helgen, F. Russell Cole, Lauren E. Helgen, Don E. Wilson: Generic Revision in the holarctic ground squirrels genus Spermophilus. Journal of Mammalogy 90 (2), 2009; Pp. 270-305. doi : 10.1644 / 07-MAMM-A-309.1
- ^ Clinton Hart Merriam : Description of a new spermophile from Southern California. North American Fauna 2, 1889; Pp. 15-16. . ( Full text )
- ↑ a b c Spermophilus (Xerospermophilus) mohavensis In: Don E. Wilson , DeeAnn M. Reeder (Ed.): Mammal Species of the World. A taxonomic and geographic Reference. 2 volumes. 3. Edition. Johns Hopkins University Press, Baltimore MD 2005, ISBN 0-8018-8221-4 .
- ^ A b Jesús A. Fernández: Phylogenetics and biogeography of the microendemic rodent Xerospermophilus perotensis (Perote ground squirrel) in the Oriental Basin of Mexico. Journal of Mammalogy 93 (6), 2012; Pp. 1431-1439. doi : 10.1644 / 11-MAMM-A-409.1
literature
- Richard W. Thorington Jr. , John L. Koprowski, Michael A. Steele: Squirrels of the World. Johns Hopkins University Press, Baltimore MD 2012, ISBN 978-1-4214-0469-1 , pp. 292-293 .
- Troy L. Best : Spermophilus mohavensis. Mammalian Species 509, 1995; Pp. 1-7. ( Full text )
Web links
- Xerospermophilus mohavensis inthe IUCN Red List of Threatened Species 2015.4. Posted by: DJ Hafner & NatureServe (G. Hammerson, DF Williams), 2008. Retrieved April 19, 2016.
- Caleb Eckloff: Spermophilus mohavensis in the Animal Diversity Net