The silky pocket mouse can be found only in western and southwestern North America. Specifically, it can be found as far west as Colorado, as far east as Texas, as far north as South Dakota, and as far south as Mexico.

Biogeographic Regions: nearctic (Native )

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: Southwestern and west-central Great Plains and intermountain plateaus from South Dakota, eastern Wyoming and southeastern Utah south through Arizona, Colorado, New Mexico, western Nebraska, western Kansas, western Oklahoma, north-central and western Texas, and the central plateau of Mexico to Puebla, Mexico; a disjunct population occurs along the coastal plain of the Gulf of California in Sonora; elevations of 975-2490 m (Patton, in Wilson and Reeder 1993; Best and Skupski 1994).

Perognathus flavus is one of the smallest mice in North America. It has soft, silky fur, short ears, and a sparsely haired tail. The dorsal area is a pinkish buff, lightly mixed with black. The ventral area is pure white. They have a conspicuous postauricular patch of buffy fur, which is usually twice as large as the ear (ear is 4-7 mm). The total length is 95-118 mm, tail length is 41-58 mm, hindfoot length is 12-18 mm, and weight is 6-9 g. The main things that will differentiate this mouse from other mice is the incredibly soft fur, small size, and relatively large ear patch. Also, the interparietal bone is more narrow than the interorbital breadth of the skull.

Range mass: 6 to 9 g.

Average basal metabolic rate: 0.097 W.

Length: 12 cm

Weight: 9 grams

Differs from allopatric P. ALTICOLUS, P. INORNATUS, and P. PARVUS in being smaller and having a relatively shorter, nonpenciled tail (Best and Skupski 1994).

Differs from P. AMPLUS in having a nonpenciled tail that is shorter, a tail that is always shorter than the head and body (Hoffmeister 1986), shorter hind feet (rarely longer than 18 mm vs. rarely shorter than 19 mm), a more conspicuous pale-colored postauricular patch, and a smaller skull (see Best and Skupski 1994).

In the Great Plains, differs from P. FASCIATUS in being smaller and in having more inflated auditory bullae, a narrower interbullar region, a shorter tail, conspicuous postauricular patches, and a shorter, broader skull (see Best and Skupski 1994).

Differs from P. FLAVESCENS in having narrower interparietals (average less than 3.6 mm vs. more than 4.0 mm in Great Plains FLAVESCENS), generally darker dorsal coloration (due to numerous black-tipped guard hairs), and larger, more contrasting postauricular patches; in Arizona, hind foot length averages 16.8 mm vs. 19.4 mm in FLAVESCENS; in New Mexico, total length usually is less than 120 mm and cranium length is less than 21 mm, vs. total length usually at least 120 mm cranium length more than 21 mm in FLAVESCENS; in Chihuahua, FLAVUS has longer ears relative to length of head and body (see Best and Skupski 1994 for further details).

Differs from P. LONGIMEMBRIS in having an absolutely and relatively shorter, nonpenciled tail, smaller average size, smaller hind feet, narrower interorbital width, wider upper molars, and shorter nasals (see Best and Skupski 1994).

Differs from sympatric P. MERRIAMI in having a shorter tail, head-body length, and hind foot; longer, softer, and laxer pelage; darker, more contrasting middorsal color with a pinkish rather than yellowish or yellowish-orange hue; larger postauricular spots; and in several cranial features; no single set of characters will distinguish all FLAVUS from all MERRIAMI, and the two species may hybridize at a few localities (see Best and Skupski 1994 for further details).

See also Williams et al. in Genoways and Brown (1993).

• Terrestrial

The silky pocket mouse prefers to live in low valley bottoms with good soils, where they can live among weeds and shrubs and burrow in the sand. However, they are also more tolerant to harsh habitat conditions than other pocket mice; they can be found in rocky areas and hard and stony soils.

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral

Comments: Sandy, sometimes rocky, soils in arid grasslands, shrublands, and pinyon-juniper woodland, in valley bottoms, hillsides, and mesas, sometimes in rather barren areas. Habitats in Arizona include plains and desert grassland, sagebrush-cactus association, grassy bajadas (often up to the oak woodland or woodland-chaparral zone), and mesquite grassland; grassy cover may be the most important element of the habitat (Hoffmeister 1986). In New Mexico, high densities occurred in areas with sparse or clumped grass cover with considerable open spaces (see Best and Skupski 1994, which see for further details on habitat in different areas). Occupies underground burrow when inactive; burrows often open at edge of rock, in crevice, or under edge of bush. Sometimes burrows into old pocket gopher mounds; may use occupied or abandoned burrows of kangaroo rats. Sometimes under surface debris during daylight hours.

Young are born in underground burrows.

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.

The food habits of the silky pocket mouse are similar to other small pocket mice, mainly consuming seeds from various grasses and weeds. They also eat some green vegetation and some insects. They have been found to eat pigweed, goosefoot, Russian-thistle, prickly-pear, globemallow, sand-bur, phlox, juniper berries, gaura, and mustard seeds and grasses. The silky pocket mouse feeds primarily on stored seeds during midday to prepare energetically for foraging in early evening. They store much of the food that they find, placing it in their burrows. The silky pocket mouse is adapted to conserve water very efficiently. They rarely, or never, drink water. Instead, they obtain all of the moisture needed for survival through the breakdown of their food (metabolic water).

Comments: Feeds almost entirely on seeds of grasses, forbs, and woody plants. Stores food in underground burrows.

Basically solitary and intraspecifically aggressive.

Home range generally is less than 0.3 ha and home range length averages around 60 m (Best and Skupski 1994).

Population density and age composition often fluctuate greatly among seasons and years; reported density ranges up to 53/ha but generally is not more than a few per hectare in most areas (Best and Skupski 1994).

Predators include various raptors, Carnivora, and snakes.

Comments: Primarily nocturnal. Apparently hibernates December-January in some areas; in Arizona and New Mexico, may exhibit torpor and/or short periods of dormancy during adverse weather, but apparently does not hibernate for extended periods (may forage above ground in subfreezing temperatures) (Hoffmeister 1986, Best and Skupski 1994).

The breeding season extends from early spring to late fall, as pregnant females have been found from March through October. The gestation period is 28 days. Usually, females have one litter per year of 2-6 young, and there is occasionally a second litter in late summer. The silky pocket mouse becomes sexually active after its postjuvenile molt, which means that some of the individuals born early in the spring season are able to breed by late summer.

Average gestation period: 26 days.

Average number of offspring: 4.

In Texas, the breeding season is April-November. In Arizona, most births may occur in winter, spring, or summer (Hoffmeister 1986), but there are some pregnant females in all months. In New Mexico, most reproduction reportedly occurs April-July and September-October, with little or none in winter (see Best and Skupski 1994). Gestation lasts about 3-4 weeks. Litter size is 1-6 (average 3-4). Young are weaned in about 30 days. In New Mexico, young born in late summer do not becme sexually active until the following spring (see Best and Skupski 1994). Apparently 1 litter/year in much of Great Plains, 2+/year in Texas. Most individuals live only a few months; few live more than 20 months; a very few may live as long as three years (see Best and Skupski 1994).

While there is no special status assigned to the silky pocket mouse, there is an increasing concern for particular subspecies. Certain Californian subspecies (P. longimembris brevinasus, P. inornatus psammophilus, p. alticola alticola, P. longimembris pacificus) are losing a vast amount of habitat due to construction and urbanization.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Comments: There has been uncertainty as to whether subspecies merriami is specifically distinct from P. flavus. Based on morphological evidence, Wilson (1973) concluded that P. flavus merriami and P. f. gilvus probably interbreed and intergrade in eastern New Mexico and western Texas. However, an electrophoretic analysis by Lee and Engstrom (1991) indicated that introgression between flavus and merriami in western Texas and eastern New Mexico is limited; the two taxa exhibit substantial sympatry and appear to interact as distinct species. Jones et al. (1992), Baker et al. (2003), and Patton (in Wilson and Reeder 1993, 2005) accepted merriami as a distinct species. In a phylogenetic analysis based on molecular data, Riddle (1995) found that Chihuahuan P. flavus grouped with P. merriami relative to P. flavus of the Southern Intermountain Basins.

See Best (1994) for a key to the species of Perognathus.