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Chaetodipus californicusCalifornia pocket mouse

By Matthew Johnson

Geographic Range

The distribution of California pocket mice (Chaetodipus californicus) is restricted to the state of California, ranging from San Francisco Bay south to the border of Baja California, and eastward to the edge of the Central Valley. C. californicus is also encountered on the west side of the Central Valley, along the foothills of the Sierra Nevada. This species is found from the town of Auburn south, and west across the Tehachapi Mountains to the coast. (Zeiner, et al., 1990)

Habitat

C. californicus occupies a wide variety of habitats year-round within its range in the Upper Sonoran and Transition life zones. These include montane hardwood, valley foothill hardwood-conifer, valley foothill hardwood, annual grassland, sagebrush, chamise-redshank and montane chaparral, and coastal scrub. C. californicus occurs in greatest abundance in habitats where grassland and chaparral are in close proximity. In central California, this species is found at low to moderate elevations, whereas in southern California it is found primarily at moderate elevations. The species is restricted to high elevations at the southernmost portion of its range in the Sierra San Pedro Martir, with an overall range in elevation from sea level to 2400 m. (Erickson and Patten, 1999; Zeiner, et al., 1990)

  • Range elevation
    0 to 2,400 m
    0.00 to ft

Physical Description

C. californicus is large for a pocket mouse. Its overall body length is 190-224 mm, with a tail length of 103-143 mm. The tail features a distinctive tuft measuring 9-14 mm. The ears and hind feet, import characters when distinguishing C. californicus from other members of its genus, measure 9-144 mm and 24-29 mm respectively. Overall body coloration is brownish-gray on top, and yellowish-white underneath, with a distinctive brownish line on the side. Conspicuous white, grooved hairs, or spines, are found on the rump. Like the body, the tail is brownish above and light below, with a prominent tuft of hairs at its base. Ears are large for a pocket mouse, with long black or buffy hairs at their base nearly as long as the ear. Hind feet are also large, and their color is yellowish-white. The average weight for this species is 23 g.

The San Diego Pocket Mouse (C. fallax) is easily confused with C. californicus. Although the two species are largely allopatric, with C. californicus to the north and C. fallax to the south, some overlap between species ranges can occur in cismontane southern California. As mentioned above, length of the ears and hind feet are the most reliable characters for distinguishing between the two species. The ears of C. fallax are shorter and rounder, with a length of 7-9 mm and its hind feet, at 21-26 mm, are slightly smaller than those of C. californicus. (Erickson and Patten, 1999; Ingles, 1965; Whitaker, Jr., 1996)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    23 g
    0.81 oz
  • Range length
    190 to 224 mm
    7.48 to 8.82 in

Reproduction

The mating system of these animals has not been reported.

C. californicus typically produce one litter a year (occasionally two) between April and July. Litter size ranges from 2-7, with and average of 4 young. Gestation takes about 25 days, and young are typically weaned in about three weeks. Females reach reproductive maturity around the age of 3 months, which is when they reach their adult size. Little other information is available on the reproductive biology of this species. (Williams, 1999; Zeiner, et al., 1990)

  • Breeding interval
    These mice are reported to produce one litter annually.
  • Breeding season
    These mice breed between March and June, producing litters between April and July.
  • Range number of offspring
    2 to 7
  • Average number of offspring
    4
  • Average gestation period
    3-4 weeks
  • Average weaning age
    3 weeks
  • Average age at sexual or reproductive maturity (female)
    3 months

Not much is known about the parental behavior of these animals. Adult females give birth to their young in burrows dug in soft soil. The young are nursed for approximately 3 weeks. They probably disperse sometime shortly after weaning. No male parental care has been reported for these animals. (Williams, 1999; Zeiner, et al., 1990)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The longevity of this species has not been reported. However, a congener, C. fallax, was reported to have lived an amazing 8 years and 4 months in captivity--an impressive lifespan for such a small rodent. (Nowak, 1999)

Behavior

C. californicus is nocturnal and aggressively solitary. During the day they remain in their burrow systems, the entrances of which are plugged with earth to keep the temperature low and humidity high. The existence of C. californicus, like all pocket mouse species, is largely fossorial, with above ground activity reduced to the essentials of food gathering and reproduction . Above ground forays are not necessarily local, and movement of adult individuals of up to 850 m in a 24 hour period have been recorded in trapping studies. (Nowak, 1999; Zeiner, et al., 1990)

On their nightly food gathering expeditions, C. californicus endeavor to fill their external, fur-lined pouches with food. When their pockets are filled, they return to their burrows to cache the contents in small pits along the passageways. C. californicus use their forepaws to push out the contents of their pouches, sometimes turning them inside out to remove remaining seeds. (Berry and Berry, 1960)

In response to hypothermia, C. californicus can enter torpor at a variety of ambient temperatures. While this response is common to all Chaetodipus species, C. californicus is unique in that arousal is always within 24 hours. (Merritt, 1985)

Although these mice are mainly terrestrial and fossorial, they are known to be agile in climbing tinot small trees and shrubs. They are quadrupedal. (Williams, 1999)

Home Range

Trapping studies suggest an extensive home range of up to 56.74 ha. (Spiegel, et al., 1995)

Communication and Perception

These mice have a variety of means of communication. Scent marking of the territory occurs when these animals take dust baths near the periphery of their territories, depositing some of their odorous secretions (produced by glands at the base of the tail) in the dirt. C. californicus is also known to make an aggressive, tooth-chattering noise, and will growl when threatened. These animals make a higher-pitched squeal when they are injured or attacked. (Williams, 1999)

Food Habits

C. californicus is primarily a grainivore, consuming the seeds from annual grasses and forbs. Insects and leafy vegetation supplement this diet seasonally. C. californicus rarely, if ever, drinks water, obtaining its water through moisture stored in seeds and leafy vegetation. The forefeet of C. californicus are equipped with long claws, which are used to sift for seeds buried in soil. The mice then place the seeds in external cheek pouches. (Nowak, 1999; Williams, 1999; Zeiner, et al., 1990)

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

Predation

C. californicus is preyed upon by a variety of terrestrial and avian predators common in California. (Zeiner, et al., 1990)

Ecosystem Roles

As small prey items, these animals probably affect populations of their predators. As seed cachers, they likely play some role in distributing seeds. As fossorial animals, they help to aerate the soil.

Economic Importance for Humans: Positive

These animals are not known to positively affect humans.

Economic Importance for Humans: Negative

No negative impact on humans has been reported for this species.

Conservation Status

C. californicus is threatened by habitat loss where human development occurs in its range. Grazing activity of domestic livestock reduces cover necessary for predator avoidance. (Zeiner, et al., 1990)

IUCN: A subspecies, C. californicus femoralis (Dalzura pocket mouse), is listed as DD (Data deficient).

Other Comments

Studies indicate that hypothermic C. californicus show significantly higher hepatic ATP levels than non-hypothermic control groups. This suggests a metabolic heat arousal mechanism similar to that used by 13-lined ground squirrels Citellus tridecemlineatus. (Merritt, 1985)

Eight subspecies have been described in southern California: C. californicus bensoni, C. californicus bernardinus, C. californicus califonicus, C. californicus dispar, C. californicus femoralis, C. californicus mariniensis, C. californicus mesopolius,and C. californicus ochrus. (Williams, 1999)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Matthew Johnson (author), California State University, Sacramento, James Biardi (editor), California State University, Sacramento.

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

acoustic

uses sound to communicate

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

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.

fertilization

union of egg and spermatozoan

forest

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

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

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).

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.

nocturnal

active during the night

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

soil aeration

digs and breaks up soil so air and water can get in

solitary

lives alone

stores or caches food

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

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

territorial

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

visual

uses sight to communicate

viviparous

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

References

Berry, W., E. Berry. 1960. Mammals of the San Francisco Bay Region. Berkely: University of California Press.

Erickson, R., M. Patten. 1999. Identification and Distribution of Spiny Pocket Mice (*Chaetodipus*) in Cismontane Southern California. Bulletin of Southern California Academy of Sciences, 98(2): 57-65.

Ingles, L. 1965. Mammals of the Pacific States. Palo Alto: Stanford University Press.

Merritt, J. 1985. The Effects of Torpor on Adenosine Triphosphate Storage in the California Pocket Mouse, *Perognathus californicus*. Journal of Neurobiology, Biochemistry, and Physiology, 82: 297-299.

Nowak, R. 1999. Walkers Mammals of the World, Sixth Edition. Baltimore: The Johns Hopkins University Press.

Spiegel, L., M. Small, J. Tom, T. Dao. 1995. An iccurrance of long range movement in the California pocketmouse (*Chaetodipus californicus*). The Southwestern Naturalist, 40: 225-226.

Whitaker, Jr., J. 1996. National Audobon Society Field Guide to North American Mammals. New York: Chanticleer Press.

Williams, D. 1999. California Pocket Mouse (Chaetodipus californicus). Pp. 508-510 in D Wilson, S Ruff, eds. The Smithsonian Book of North American Mammals. Washington D.C., London: Smithsonian Institution Press.

Zeiner, D., W. Laudenslayer, K. Mayer, E. White, (eds.). 1990. California's Wildlife. Vol. 3, Mammals. Sacramento: California Department of Fish and Game.

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