Peromyscus californicusCalifornia mouse

Geographic Range

Peromyscus californicus is found from San Francisco Bay south and east along the coast ranges and in the eastern Sierra Nevada from Mariposa Co. south to Kern Co. in California south to Bahia San Quintin on the Pacific coast of northwestern Baja California (Bryiski and Harris, 1984; Alvarez-Casteñada and Cortés-Calva, 1999). (Brylski and Harris, 1990)


Peromyscus californicus is generally restricted to dense chaparrel and broad-sclerophyll woodland (Meritt 1974). The limiting factor for its small geographic range may be the need for naturally occurring burrow holes of the proper size for these larger animals (Grinnell and Orr 1934), as they are poor natural burrowers. The co-occurrence of woodrat houses and a distributional association with the California laurel complex have also been noted as potential limiting factors (Meritt 1974), although there is no direct evidence to implicate any of these. (Grinnell and Orr, 1934; Meritt, 1974; Merritt, 1999)

  • Range elevation
    2440 (high) m
    8005.25 (high) ft

Physical Description

Peromyscus californicus is the largest species in its genus. Its total length is between 220-285 mm, with tail length ranging from approximately 117-156 mm (Whitaker 1997). It is distinctly bicolored. Adults have a yellowish brown or gray mixed with black dorsal coloring, and a white underside, and feet. Many individuals have a distinctly fulvous throat patch and a fulvous lateral line separating dorsal from ventral pelage in the shoulder region, sometimes extending to the thigh. Juveniles are gray on top with a white underside. The tail matches the dorsal pelage and is not sharply bicolored. The ears are large, ranging from 20-25 mm (Whitaker 1997).

  • Sexual Dimorphism
  • male larger
  • Range mass
    33.2 to 54.4 g
    1.17 to 1.92 oz
  • Range length
    220 to 285 mm
    8.66 to 11.22 in
  • Average basal metabolic rate
    0.267 W


Unlike most mice P. californicus is truly monogamous, and once mated will stay paired for life (McCade and Blanchard 1950; Ribble 1991; Ribble and Salvioni 1990; Guvernick and Nelson 1990). (McCabe and Blanchard, 1950; Ribble, 1992)

Mating may occur year round, but mainly from March to September. In the lab P. californicus can have up to 6 litters per year, but in the wild the average is 3-4. Gestation is 30 to 33 days and average litter size is 2 (from 1 to 3), with a slight increase in litter size with the age of the female. Compared to other species of Peromyscus, P. californicus young are rather precocious, although weaning is not completed for about 5 weeks. They also have a long period before reaching sexual maturity, approximately 11 weeks for females and even longer for males. (McCabe and Blanchard, 1950)

  • Breeding interval
    Females can have up to 6 litters per year, but 3 to 4 is more typical.
  • Breeding season
    Breeding can occur year round but most breeding occurs from March to September.
  • Range number of offspring
    1 to 3
  • Average number of offspring
  • Range gestation period
    30 to 33 days
  • Average weaning age
    5 weeks
  • Average age at sexual or reproductive maturity (female)
    11 weeks
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    46 days
  • Range age at sexual or reproductive maturity (male)
    11 (low) weeks

Males help extensively in caring for and protecting the young. (Merritt, 1999)

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


California mice generally live for 9 to 18 months. Populations tend to be fairly stable and at low densities, as compared to other Peromyscus species. (Merritt, 1999)

  • Typical lifespan
    Status: wild
    9 to 18 months
  • Average lifespan
    Status: captivity
    5.5 years


Peromyscus californicus is nocturnal, with a slight activity peak just before dawn (Hudson 1967). Usually a docile mouse, it will actively defend its nest from conspecifics of the same sex. A poor burrower, Peromyscus californicus readily uses woodrat (Neotoma fuscipes) houses for dens, and where found together, P. californicus actively excludes its conspecific P. truei from these woodrat houses (Meritt 1974). They build globular nests out of grasses or sticks, lined with fine grass. California mice are excellent climbers and are often found in trees and shrubs. Males and females form long-term pair bonds and these mice live in small family groups. (Meritt, 1974; Merritt, 1999)

Communication and Perception

Like other Peromyscus species, California mice have keen vision and hearing and use chemical cues extensively in communication.

Food Habits

Peromyscus californicus specializes on the fruits, seeds and flowers of shrubs (Meserve 1976). In woodland habitat the seeds of California bay laurel (Umbellularia californica) are the major food (Meritt 1974). Arthropods may make up a small percentage on the diet but these are not actively hunted (Meserve 1976). Water is most likely obtained from the food that it eats and supplimented with dew; P. californicus is not as good at water conservation as other species in the genus (Meritt 1974). (Meritt, 1974; Merritt, 1999; Meserve, 1977)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit
  • flowers


California mice, like other Peromyscus species, are an important prey base for many predators throughout their range. They are preyed on by hawks, owls, rattlesnakes, and small mammalian predators. Their nocturnal and secretive habits help to protect them from many predators.

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

California mice are important seed predators in the ecosystems in which they live and they form an important prey base for rattlesnakes, owls, and other predators.

Economic Importance for Humans: Negative

Like other members of Peromyscus, California mice fecal matter may transmit hantavirus.

  • Negative Impacts
  • injures humans
    • carries human disease

Conservation Status

Despite its relatively narrow habitat, limited geographic range, and generally low population densities, Peromyscus californicus populations remain healthy. (Merritt, 1999)


Tanya Dewey (editor), Animal Diversity Web.

Amy Jess (author), University of California, Berkeley, James Patton (editor), University of California, Berkeley.



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


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.


Referring to an animal that lives in trees; tree-climbing.

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.


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.


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.


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 fruit


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 one mate at a time.


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.


active during the night

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


associates with others of its species; forms social groups.


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.


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.

year-round breeding

breeding takes place throughout the year


Brylski, P., J. Harris. 1990. California's Wildlife Volume III. Sacramento, California: California Department of Fish and Game.

Cranford, J. 1982. The effects of Woodrat houses on population density of Peromyscus. Journal of Mammalogy, 63: 663-666.

Grinnell, J., R. Orr. 1934. Systematic review of the californicus group of the rodent s of the genus Peromyscus. Journal of Mammalogy, 15: 210-220.

McCabe, T., B. Blanchard. 1950. Three species of Peromyscus. Santa Barbara, California: Rood Association.

Meritt, J. 1974. Factors influencing the local distribution of Peromyscus californicus in Northern California. Journal of Mammalogy, 55: 102-113.

Merritt, J. 1999. California mouse. Pp. 565-566 in D Wilson, S Ruff, eds. The Smithsonian Book of North American Mammals. Washington, D.C.: Smithsonian Institution Press.

Meserve, P. 1977. Three-dimensional home ranges of cricetid rodents. Journal of Mammalogy, 58: 549-558.

Ribble, D. 1992. Lifetime reproductive success and its correlates in the monogamous rodent, Peromyscus californicus. Journal of Animal Ecology, 61: 457-468.