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Perognathus flavus

Baird, 1855

Silky Pocket Mouse

G5Secure Found in 2 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.103740
Element CodeAMAFD01030
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassMammalia
OrderRodentia
FamilyHeteromyidae
GenusPerognathus
Other Common Names
silky pocket mouse (EN)
Concept Reference
Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at: http://www.nmnh.si.edu/msw/.
Taxonomic Comments
There are 14 recognized subspecies of P. flavus, although some questions remain regarding the taxonomy.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2021-06-25
Change Date1996-11-07
Edition Date2021-08-04
Edition AuthorsSears, N. (2021)
Threat ImpactUnknown
Range Extent>2,500,000 square km (greater than 1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
This species is ranked as secure in view of its wide distribution, stable population trends, and lack of substantial immediate threats (although invasive grasses are a growing threat). There is an isolated subspecies in Arizona (P. f. goodpastori) that is considered threatened due to its restricted range.
Range Extent Comments
This species occurs in the southwestern and west-central Great Plains and intermountain plateaus in the US 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, extending to the central plateau of Mexico to Puebla, Mexico. A disjunct population occurs along the coastal plain of the Gulf of California in Sonora, Mexico. It occurs at elevations of 975-2490 meters.
Occurrences Comments
This species is represented by a large number of occurrences (subpopulations) (e g. see map in VertNet 2020).
Threat Impact Comments
Overall threats are likely to be low, however, some possible stressors include habitat loss and degradation due to cattle grazing and conversion to cropland, invasive species (e.g. nonnative plants such as Cheat Grass, Bromus tectorum), and pollution/littering (e.g. being trapped and killed in discarded bottles and cans) (Johnson and Geluso 2019). Climate change can cause shifts in Silky Pocket Mouse populations, however results by Cárdenas et al. (2021) predicted that this species may benefit as climates become more variable, and its sensitivity to climate will depend on how the ecosystem modulates thermal or desiccation thresholds. A study on the effects of fire and livestock grazing on rodent numbers at a desert grassland site in Arizona found this species responded positively to fire in ungrazed grasslands (Bock et al. 2011).

This species has been shown, experimentally, to be highly susceptible to plague (Holdenreid and Quan 1956). Poisoning to control other species of rodents is also a possible threat. Finally, competition with sympatric congeners may limit P. flavus to some extent, but this is somewhat speculative, and the species certainly co-exists with several congeners in various parts of its range. In Utah, there is an "inverse" relationship between the abundances of P. flavus and P. flavescens in places where they co-occur (G. Oliver, pers. comm. 2021). Williams (1978) discussed possible competition and displacement.

In Wyoming, energy developments (wind, natural gas, and oil) are in all phases of development and planning that will impact a large portion of the species’ range and may lead to increased cover of invasive grasses. In sagebrush ecosystems, Peromyscus mice increase dramatically in energy development areas which could change competition dynamics (I. Abernathy, pers. comm. 2021). In eastern Wyoming, various invasive grasses such as Ventenata grass (Ventenata dubia) and Medusahead (Taeniatherum caput-medusae) are increasing, degrading habitat for the species (I. Abernathy, pers. comm. 2021).
Ecology & Habitat

Description

A small mouse (the smallest heteromyid) with fur-lined cheek pouches, upperparts finely lined with black on ochraceous buff (and in some subspecies yellowish-buff and pinkish-buff), a faint buff lateral line, white underparts (may be a faint tawny suffusion), and clear buffy postauricular patches; dorsal pelage color, particularly the abundance of black hairs, varies geographically; the tail is buffy or dusky dorsally, whitish ventrally; length of head and body averages about 60 mm in adults; tail is shorter than the head and body and averages less than 57 mm and rarely is more than 60 mm; mass is 6-10 g. See Best and Skupski (1994) for cranial characteristics and other further details.

Diagnostic Characteristics

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).

Habitat

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.

Ecology

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.

Reproduction

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).
Terrestrial Habitats
Shrubland/chaparralGrassland/herbaceousDesert
Other Nations (1)
United StatesN5
ProvinceRankNative
UtahS3Yes
ArizonaS5Yes
NebraskaS1Yes
Navajo NationS5Yes
South DakotaSUYes
OklahomaSNRYes
New MexicoS5Yes
KansasS4Yes
WyomingS3Yes
TexasS5Yes
ColoradoS3Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureUnknownUnknownHigh (continuing)
2.3 - Livestock farming & ranchingUnknownUnknownHigh (continuing)
5 - Biological resource useUnknownUnknownHigh (continuing)
5.1 - Hunting & collecting terrestrial animalsUnknownUnknownHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesUnknownUnknownHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesUnknownUnknownHigh (continuing)
9 - PollutionUnknownUnknownHigh (continuing)
9.4 - Garbage & solid wasteUnknownUnknownHigh (continuing)
11 - Climate change & severe weatherUnknownUnknownHigh (continuing)

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Roadless Areas (2)
Arizona (1)
AreaForestAcres
Lower San FranciscoApache-Sitgreaves National Forests59,310
New Mexico (1)
AreaForestAcres
Peloncillo (NM)Coronado National Forest43,339
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