Because they use energy and water so efficiently, Little Pocket Mice can inhabit some of the driest and least vegetated parts of North America. They are abundant in deserts of the southwestern United States and northwestern Mexico, and readily inhabit coastal sage, shrub-steppe, and open grasslands in those regions. This Mouse is able to get by on the water generated through its normal metabolic processes. Its urine and feces are so concentrated, and evaporation is so reduced, that it never requires a drink. When given the choice, Little Pocket Mice invariably select the warmest available environment (below about 30° C). During the summer they inhabit the shallow, warmer parts of the burrow system. When it is cold, the Mice move deeper into the burrow where temperatures are warmest. They typically remain underground for months every year, frequently in a state of torpor, their metabolism and body temperatures lowered, waking occasionally to feed on the seeds they have stored.

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Mammal Species of the World

The species' distribution extends from southeast Oregon and western Utah in the United States, to north Sonora and Baja California Sur in Mexico.

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Western U.S. and northwestern Mexico: southeastern Oregon and southwestern Idaho south through eastern, central and southern California, Nevada, western and southern Utah, and scattered parts of Arizona to northern Baja California and western Sonora. Does not occur in central California west of the Sierra Nevada (Williams et al. 1993).

Length: 15 cm

Weight: 9 grams

Sexual Dimorphism: None

Length:
Average: 131 mm
Range: 110-151 mm

Weight:
Range: 6.5-10.5 g

Differs from Chaetodipus spp. in softer pelage that lacks spines or bristles (see Hall 1981 for cranial differences between Chaetodipus and Perognathus). Differs from P. ALTICOLUS, P. XANTHONOTUS, P. PARVUS, and P. FORMOSUS in smaller hind foot (less than 20 mm vs. more than 20 mm), unlobed antitragus, and occipitonasal length usually less than 24 mm rather than usually more than 24 mm (Hall 1981). Differs from P. FASCIATUS, P. FLAVUS, and P. FLAVESCENS in having the tail longer than the head and body rather than equal to or shorter than the head and body. Adults differ from P. AMPLUS in smaller size (maximum total length 15 cm vs. 17 cm) and shorter tail (usually 67-81 mm vs. 75-88 mm; less than 75% of head and body length in LONGIMEMBRIS, more than 75% in AMPLUS) (Hall 1981, Hoffmesiter 1986); see Hoffmeister (1986) for a detailed account of the differences between the very similar P. LONGIMEMBRIS and P. AMPLUS. Differs from P. INORNATUS in smaller mastoidal bullae.

Habitat and Ecology

Systems

• Terrestrial

Comments: Sandy soil in valleys; firm sandy soil, overlain with pebbles, on slopes with widely spaced shrubs. In sagebrush, creosote bush, and cactus communities in Lower and Upper Sonoran life zones. Young are born in a nest in an underground burrow.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Comments: Feeds primarily on seeds, plus green vegetation in spring. Forages mainly under shrub canopy. Stores food in underground burrow.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

10,000 to >1,000,000 individuals

Primarily solitary. Populations may fluctuate markedly from year to year and seasonally. In some areas this is the most abundant mammal; populations have been estimated to be as high as 400/acre (Hall 1946); other estimates generally have been not more than about 1-6/ha (see Zeiner et al. 1990). Home range size generally averages not more than a few hectares (see Zeiner et al. 1990).

Comments: Remains in den during severe weather. Not active above ground during cold weather (Hall 1946); hibernates 6.5 months in southeastern California (Kenagy and Bartholomew 1985). In spring most active 2-5 hours after sunset, second peak just before sunrise (Hoffmeister 1986).

Maximum longevity: 8.3 years (captivity) Observations: Specimens have been reported to live 8.3 years in the laboratory (Ronald Nowak 1999).

Breeding season generally peaks in spring, varies with temperatures, food supply, and plant growth. Produces 1 (usually) or 2 litters/year, 2-8 young/litter. Gestation lasts 21-31 days. Young are weaned in 30 days. Sexually mature in 2-5 months. May not reproduce in years with below average precipitation (Kenagy and Bartholomew 1985).

The following is a representative barcode sequence, the centroid of all available sequences for this species. 

 
There are 2 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
 

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Species: 2
Species With Barcodes: 1

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Large range in western North America; common in many areas.

Perognathus longimembris pacificus, the Pacific pocket mouse, is a Critically Endangered subspecies; the subspecies P. longimembris brevinasus, the Los Angeles pocket mouse, is Vulnerable.

Population

Population Trend

Major Threats

Conservation Actions

Comments: Has been regarded as possibly conspecific with P. amplus (Hoffmeister 1986); amplus and longimembris were regarded as distinct species by Jones et al. (1992) and Patton (in Wilson and Reeder 1993, 2005). McKnight (1995) examined mtDNA variation in populations in and around Arizona and concluded that P. amplus and P. longimembris are distinct lineages that have completed the speciation process. Williams et al. (1993) referred P. l. psammophilus (and synonym sillimani) to P. inornatus. Based on molecular data, Riddle (1995) found a phylogenetic distinction between P. longimembris and P. inornatus, though these taxa formed a clade relative to P. amplus.

See McKnight and Lee (1992) for information on karyotypic variation. See Best (1994) for a key to the species of Perognathus.