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Perognathus flavussilky pocket mouse

By Todd Brilliant

Geographic Range

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.

Habitat

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.

Physical Description

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
    0.21 to 0.32 oz
  • Average basal metabolic rate
    0.097 W
    AnAge

Reproduction

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.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    4
    AnAge
  • Average gestation period
    26 days
    AnAge

Behavior

The silky pocket mouse constructs burrows at the base of plants like yucca, cactus, or shrubs. There are usually 2-3 entrances to each burrow, and the openings are plugged during the day. The burrows have blind side tunnels used for defecation and food storage. One individual may maintain more than one burrow system. The silky pocket mouse constructs nests out of grasses and weeds. They primarily live underground for the 5 coldest months of the year, and go through periods of torpor that last approximately 48 hours each. Other than these brief periods of torpor, they remain active all winter long and forage above ground almost nightly. The silky pocket mouse is generally sedentary, and tends not to move more than 40-60 m from their burrows.

Communication and Perception

Food Habits

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).

Conservation Status

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.

Contributors

Todd Brilliant (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

1993. World Checklist of Threatened Mammals. Peterborough: Joint Conservation Committee.

1994. "The Mammals of Texas- Online Edition" (On-line). Accessed September 30, 1999 at www.nsrl.ttu.edu/tmot/perflalvu.html.

1997. "World Conservation Monitoring Centre" (On-line). Accessed November 9, 1999 at http://www.wcmc.org.uk.

Fitzgerald, J. 1994. Mammals of Colorado. Niwot: Denver Museum of Natural History.

Nowak, R. 1997. "Electronic Walkers Mammals Of The World" (On-line). Accessed September 30, 1999 at www.press.jhu.edu/books/walkers_mammals_of_the_world/rodentia/heteromyidae.perogn -athus.html.

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