Mohave ground squirrel (Xerospermophilus mohavensis)

Description

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Mohave ground squirrel fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Mohave ground squirrel description

The Mohave ground squirrel (Xerospermophilus mohavensis) is a calm, solitary ground squirrel ⁽³⁾, with a uniformly brown or pink-brown upperside, which contrasts with its cream-white underside ^{(3) (4)}. The lack of markings on its back makes this species one of the only uniformly-coloured ground squirrels throughout most of its range ⁽⁵⁾.

The tail of the Mohave ground squirrel is short and tufted ⁽³⁾, and is generally narrower at the base and somewhat banded near the tip ⁽⁴⁾. The underside of the tail is creamy-white ^{(3) (4) (5) (6) (7)}, and the tail is often held up against the squirrel’s back, hiding the grey-brown upperside ^{(3) (6)}. The ears of the Mohave ground squirrel are small ⁽⁴⁾ and the large, round eyes are surrounded by a pale ring ⁽³⁾, which is conspicuous against its brown cheeks ^{(3) (7)}.

The feet of the Mohave ground squirrel are large with long, curved claws on the toes and a long, blunt claw on the thumb ⁽³⁾. The front feet are pink-brown or pink-cinnamon and have hairless palms, while the palms of the hind feet are heavily furred ⁽³⁾.

The male, female and juvenile Mohave ground squirrel are all similar in appearance ⁽³⁾.

Although it is usually silent, the Mohave ground squirrel sometimes produces both low and shrill whistles, as well as a high-pitched ‘peep’ ^{(3) (4)}. The young of this species are capable of producing a high-pitched squeak, which is thought to be associated with feeding ⁽³⁾. 

Synonyms

Spermophilus mohavensis.

Size

Total length: 21 - 23 cm ⁽²⁾

Head-body length: 12.8 - 16.5 cm ⁽³⁾

Tail length: 5.7 - 7.2 cm ⁽²⁾

Pre-aestivation weight: 165 - 300 g ⁽²⁾

Post- aestivation weight: 70 - 80 g ⁽²⁾

Mohave ground squirrel biology

A generally solitary species ^{(3) (4)}, the Mohave ground squirrel is only gregarious during the mating season in early spring, when the male and female will enter a burrow within the male’s territory for several hours to mate ⁽³⁾. After copulation, the female usually stays within the male’s territory the following day, then leaves to establish its own home range ⁽³⁾. In March or April ⁽²⁾, the female gives birth to a litter of between 4 and 9 young, after a gestation period of 29 or 30 days. The young ground squirrels are usually weaned after around 32 days ^{(3) (4)}. In years of drought, the Mohave ground squirrel may not reproduce ^{(2) (3)}.

In spring and early summer ⁽⁵⁾, the Mohave ground squirrel is active above ground, coinciding with the growing season of green plants ⁽³⁾. During this time, seeds, fungi, fruits and forbs are most abundant, which are the primary components of the Mohave ground squirrel’s diet ^{(2) (4) (6) (9)}. However, this species is omnivorous ⁽³⁾, and arthropods such as caterpillars are also taken ⁽⁴⁾. The late winter months and early summer are spent accumulating fat for aestivation ⁽⁹⁾, with some individuals gaining up to 200 grams in weight ⁽³⁾. During the time the Mohave ground squirrel is active, it is diurnal, and although it is a ground squirrel, it is occasionally known to climb Joshua trees while foraging ^{(3) (4)}.

Aestivation begins in August and ends in February or March ^{(2) (3) (4)}, with males generally emerging up to two weeks earlier than females ⁽³⁾. The Mohave ground squirrel occupies three different burrows: a home burrow used to sleep in during the active period, an accessory burrow which is used for social interactions and thermoregulation, and an aestivation burrow, where it spends six or seven months aestivating ⁽³⁾. The burrows built by the Mohave ground squirrel are usually around 5.5 metres long and 1 metre deep ^{(3) (4)}. 

Mohave ground squirrel range

The Mohave ground squirrel is endemic to the northwest Mohave Desert in California, United States ^{(2) (3) (4) (8)}.

Mohave ground squirrel habitat

The Mohave ground squirrel is found in open areas ⁽³⁾, such as deserts ⁽²⁾, where there is an abundance of herbaceous, shrubby plants and sandy or gravelly soil, which this species uses to build burrows ^{(2) (3) (4) (5) (7)}.

The Mohave ground squirrel is found between elevations of 610 and 1,800 metres ⁽²⁾, where there are plenty of creosotebush (Larrea tridentate), saltbush (Atriplex spp.) and Joshua trees (Yucca brevifolia) ^{(3) (5) (8)}.

Mohave ground squirrel status

The Mohave ground squirrel is classified as Vulnerable (VU) on the IUCN Red List ⁽²⁾.

Mohave ground squirrel threats

The patchy and fragmented distribution of Mohave ground squirrel populations increases this species’ vulnerability to local extinctions, especially during times of drought when most reproduction is halted ^{(2) (3) (9)}. The range of the Mohave ground squirrel has been greatly reduced due to urbanisation, agriculture and military land use ^{(2) (3) (5) (8)}. Off-road vehicle use is permitted in certain parts of this species’ range, and is highly destructive to the habitat ⁽²⁾.

Rodenticides are used in areas occupied by the Mohave ground squirrel, especially in alfalfa plantations, which are an important food source for some populations ⁽³⁾. The specific habitat requirements of this species means that many areas throughout its range are unsuitable for it ⁽²⁾. 

Mohave ground squirrel conservation

Part of the Mohave ground squirrel’s range falls within a number of protected areas, offering it a certain degree of protection, although this may be insufficient for its future conservation ⁽²⁾. The habitat of the Mohave ground squirrel needs protection from development and off-road traffic to prevent local extinctions from occurring ^{(2) (9)}. Improving the existing habitat by restoring disturbed vegetation, modifying grazing practices and banning rodenticide use could be vital to the survival of this threatened rodent ^{(2) (9)}.

The West Mojave Coordinated Management Plan could provide protection for certain areas within the Mohave ground squirrel’s range, although areas of suitable habitat must first be identified for this method of conservation to be successful ⁽⁹⁾.

The Mohave ground squirrel was listed as ‘threatened’ in 2011 by the California Department of Fish and Game and is therefore protected under the California Endangered Species Act ⁽¹⁰⁾.

More research needs to be done into various aspects of the Mohave ground squirrel’s biology, including studies on its reproduction, dispersal, feeding habits, population size, the genetic variation within populations and the effects of certain threats, to ensure that effective conservation measures can be established and implemented ^{(2) (9)}.

Find out more

Find out more about the Mohave ground squirrel and the conservation of other North American rodents:

• Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents:Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at: 
  http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
• Best, T.L. (1995) Spermophilus mohavensis. Mammalian Species, 509: 1-7. Available at:
  http://www.science.smith.edu/msi/pdf/i0076-3519-509-01-0001.pdf

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Glossary

Aestivation

Period of dormancy occurring the summer or dry season, comparable to hibernation in winter.

Arthropods

A major grouping of animals that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).

Diurnal

Active during the day.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Forb

Any herbaceous (non-woody) flowering plant that is not a grass.

Genetic diversity (genetic variation)

The variety of genes within a particular species, population or breed causing differences in morphology, physiology and behaviour.

Gestation

The state of being pregnant; the period from conception to birth.

Herb

A small, non-woody, seed bearing plant in which all the aerial parts die back at the end of each growing season.

Home range

The area occupied by an animal during routine activities, which is not actively defended.

Omnivorous

Feeding on both plants and animals.

Territory

An area occupied and defended by an animal, a pair of animals or a group.

Thermoregulate

To control body temperature.

References

1. Helgen, K.M., Cole, F.R., Helgen, L.E. and Wilson, D.E. (2009) Generic revision in the holarctic ground squirrel genus Spermophilus. Journal of Mammalogy, 90(2): 270-305.
2. IUCN Red List (April, 2012)
   http://www.iucnredlist.org/
3. Best, T.L. (1995) Spermophilus mohavensis. Mammalian Species, 509: 1-7. Available at:
   http://www.science.smith.edu/msi/pdf/i0076-3519-509-01-0001.pdf
4. Reid, F. (2006) A Field Guide to the Mammals of North America, North of Mexico. Peterson Field Guides, New York.
5. Bowers, N., Bowers, R. and Kaufman, K. (2007) Kaufman Field Guide to Mammals of North America. Houghton Mifflin Harcourt, New York.
6. Feldhamer, G.A., Thompson, B.C. and Chapman, J.A. (Eds.) Wild Mammals of North America: Biology, Management, and Conservation. Second Edition. The Johns Hopkins University Press, Baltimore.
7. Kays, R.W. and Wilson, D.E. (2009) Mammals of North America. Princeton University Press, Princeton.
8. Bell, K.C. and Matocq, M.D. (2010) Development and characterisation of polymorphic microsatellite loci in the Mohave ground squirrel. Conservation of Genetic Resources, 2(2): 197-199. Available at:
   http://www.cabnr.unr.edu/matocq/publications/Xerospermophilus_primers.pdf
9. Hafner, D.J., Yensen, E. and Kirkland Jr, G.L. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at: 
   
   http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
10. California Department of Fish and Game (2011) State and Federally Listed Endangered and Threatened Animals of California. California Department of Fish and Game, California. Available at:
    http://www.dfg.ca.gov/biogeodata/cnddb/pdfs/TEAnimals.pdf