Peromyscus trueipinyon mouse

Geographic Range

Pinyon mice can be found as far east as the panhandle of north Texas and as far west as the Pacific coast. The northern limit of their range is central Oregon, and the southern limit is southern Mexico. (Hoffmeister, et al., 1981; Wilson and Ruff, 1999)


Pinyon mice are terrestrial mammals that can be found at altitudes ranging from sea level to elevations of greater than 2300 meters. They frequent arid or semi-arid climates, preferring brushland and desert, and are typically found near pinyon junipers, hence their common name. However, pinyon mice can also be found in open, grassy habitats, as well as landscapes including canyons, redwoods, yellow pine belts, sagebrush, scrub oak, boulders, cacti, and rocky slopes. Pinyon mice are able to endure warm, dry summers in addition to snowy winters. They make dens under rock ledges, outcrops, stone shelves and slabs, and in live or dead trees. (Hall and Morrison, 1997; Hoffmeister, et al., 1981; King, 1968; Wilson and Ruff, 1999)

  • Range elevation
    0 to greater than 2300 m
    0.00 to ft

Physical Description

Pinyon mice have long, silky fur that ranges from yellow-brown to dark gray on the back and fades to white on the under parts and feet. They may or may not have a pectoral spot. The tail is tipped with long hairs and has a dark dorsal stripe running down its length. The hind feet are large, and are typically 22 mm or more in length. Juveniles have gray pelage that changes with a series of molts, starting at 7 weeks and finishing at 10 to 11 weeks of age. Coat color matches the habitat regionally, allowing these mice to blend into vegetation and hide from predators. Males and females are similar in size, the average weight is about 20 g, and the head and body length ranges between 171 to 231 mm. Tail length varies from 76 to 123 mm. The size of pinyon mice often varies with location; pinyon mice in the western parts of their range tend to have a longer tail, smaller body size, smaller ears, and smaller hind feet than their counterparts in the east. (Hoffmeister, et al., 1981; King, 1968; Wilson and Ruff, 1999)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    20 g
    0.70 oz
  • Average mass
    25 g
    0.88 oz
  • Range length
    171 to 231 mm
    6.73 to 9.09 in
  • Average basal metabolic rate
    0.307 W


Pinyon mice have a promiscuous mating system in which females nest in small territories and males seek mating opportunities with nearby females. (Ribble and Stanley, 1998)

Although mating can occur in all seasons, pinyon mice breed primarily from mid-February to mid-November with a peak between April and June. Females give birth to a litter of three to six pups after a gestation period of approximately 26 days, though gestation may be as long as 40 days if the female is lactating. Females first come into estrus at approximately 50 days of age, and males are capable of inseminating females at approximately 9 weeks of age. (Hoffmeister, et al., 1981; King, 1968; Scheibe and O'Farrell, 1995; Scheibe, 1984; Wilson and Ruff, 1999)

  • Breeding interval
    Pinyon mice breed at intervals as frequent as once monthly.
  • Breeding season
    Pinyon mice will breed at any time between February and mid-November with a peak between April and June.
  • Range number of offspring
    3 to 6
  • Average number of offspring
  • Range gestation period
    40 (high) days
  • Average gestation period
    26 days
  • Range weaning age
    3 to 4 weeks
  • Range time to independence
    3 to 4 weeks
  • Average age at sexual or reproductive maturity (female)
    50 days
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    50 days
  • Average age at sexual or reproductive maturity (male)
    9 weeks

Newborn pinyon mice weigh around 2.3 grams at birth, and they are born completely hairless with their ears and eyes folded shut. The pups are capable of squeaking at one week of age, and their bodies are covered in hair by day 14. The pups nurse for three to four weeks, at which point they become independent. Females exclusively care for their young in a nest until they are weaned. (Wilson and Ruff, 1999)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


The lifespan of pinyon mice and other mice in the genus Peromyscus has not been studied in detail. An individual Peromyscus maniculatus lived to be eight years old in captivity, but studies have shown that mice in this genus rarely live more than a year in the wild. Only 20% of the young in each nest will survive their first year of life, and only 2-3% of adults live long enough to breed in consecutive seasons. (Hoffmeister, et al., 1981; King, 1968)

  • Average lifespan
    Status: wild
    1 years
  • Average lifespan
    Status: captivity
    5.4 years


Pinyon mice are nocturnal rodents that sleep periodically throughout the day. They are excellent climbers, frequently using their long tails for balance. Studies have shown that pinyon mice are more active foragers when ambient temperatures are higher. Pinyon mice are less active on moonlit nights, most likely because there is an increased risk of predation when it is brighter outside. In times of severe drought, pinyon mice can increase urine concentration, reduce the moisture content of their feces, and drop into a diurnal torpor to save energy. (Hall and Morrison, 1997; Hoffmeister, et al., 1981; King, 1968; Ribble and Stanley, 1998; Scheibe and O'Farrell, 1995; Scheibe, 1984)

Home Range

Pinyon mice frequently use multiple den sites during the day. Male dens are typically farther apart from each other than female dens, but the territories of males tend to overlap each other more than the territories of females. In general, male territories are larger, while female territories are smaller because females are constrained to their dens during breeding. This reproductive constraint is the basis for their promiscuous mating system in which males must search for females. (Hall and Morrison, 1997; Hoffmeister, et al., 1981; King, 1968; Ribble and Stanley, 1998; Scheibe and O'Farrell, 1995; Scheibe, 1984)

Communication and Perception

Communication in pinyon mice hasn't been well-studied. They are likely to use visual, auditory, chemical, and tactile modes of communication.

Peromyscus species are known for their acute senses of hearing and smell, which they use to navigate, find food, and escape predation at night. Their enlarged eyes suggest they have a well-developed sense of vision in low light conditions. Their long whiskers are used for tactile perception.

Food Habits

Pinyon mice are primarily frugivorous and granivorous, although they will also readily eat insects, spiders, and other invertebrates. Adults typically feed on juniper seeds (Juniperus) and berries in the winter and acorn mast (Quercus) in the summer. Pinyon mice are notorious at caching their food supply; they frequently dig holes and bury their food in various places around their territory, particularly around den sites. These cache networks may become quite extensive. Finally, pinyon mice are capable of surviving on a very limited water supply, which is crucial to their survival in the arid habitats they occupy. (Hoffmeister, et al., 1981; King, 1968; Wilson and Ruff, 1999)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit


Predation on pinyon mice has not been well studied, although predation most likely plays a role in the high mortality rate of these rodents. Their primary predators are owls, diurnal birds of prey, and snakes, especially rattlesnakes. They escape predation by remaining inactive during the day in dens, by their cryptic coloration, and by their acute senses at night. (King, 1968)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Pinyon mice are almost always found near pinyon junipers, hence their common name. Juniper seeds are the main food source of pinon mice, making them, like other members of the genus Peromyscus, significant predators of conifer seeds. Thus they impact their communities by impacting the composition of the plant community. Their seed caching behavior may also result in germination of seeds. Pinyon mice are also an important and abundant source of prey for many avian and mammalian predators. (King, 1968)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

It is not known whether pinyon mice have positive affects on human populations, aside from their important ecosystem roles.

Economic Importance for Humans: Negative

Pinyon mice serve as an important reservoir for several types of parasites. Some have speculated that they are capable of carrying plague-infested fleas, but this has not been well documented. Members of the genus Peromyscus are capable of carrying chiggers, a common pest, as well as the ticks that transmit Rocky Mountain Spotted Fever and Lyme disease to humans. Peromyscus species are also important reservoirs for hantaviruses. (King, 1968)

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

Pinyon mice are not currently threatened throughout much of their range. However, since pinyon junipers are a crucial part of their habitat, destruction of such habitats can imperil these mice. The subspecies Peromyscus truei comanche, found in the pandhandle of northwestern Texas, is considered near threatened by the IUCN. (King, 1968)


Tanya Dewey (editor), Animal Diversity Web.

Jennifer Gumas (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University.



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


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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.


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.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats seeds


An animal that eats mainly plants or parts of plants.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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


active during the night


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


remains in the same area


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


lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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.


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.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Hall, L., M. Morrison. 1997. Den and Relocation Site Characteristics and Home Ranges of <<Peromyscus truei>> in the White Mountains of California. Great Basin Naturalist, 57 (2): 124-130.

Hoffmeister, D., D. Williams, S. Anderson, T. Lawlor. 1981. Mammalian Species #161: <<Peromyscus truei>>. Pp. 1-5 in Mammalian Species, Vol. 151-200. The American Society of Mammalogists.

King, J. 1968. Biology of <<Peromyscus>> (Rodentia). The United States of America: The American Society of Mammalogists.

Ribble, D., S. Stanley. 1998. Home Ranges and Social Organization of Syntopic <<Peromyscus boylii>> and <<P. truei>>. Journal of Mammalogy, 79 (3): 932-941.

Scheibe, J. 1984. The Effects of Weather, Sex, and Season on the Nocturnal Activity of <<Peromyscus truei>> (Rodentia). The Southwestern Naturalist, 29 (1): 1-4.

Scheibe, J., M. O'Farrell. 1995. Habitat Dynamics in <<Peromyscus truei>>: Eclectic Females, Density Dependence, or Reproductive Constraints?. Journal of Mammalogy, 76 (2): 368-375.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington and London: Smithsonian Institution Press.