Chaetodipus formosuslong-tailed pocket mouse

Geographic Range

Chaetodipus formosus is found in the western United States including southern Nevada, western Utah, southeastern California into the Baja peninsula, and the northwest corner of Arizona. Chaetodipus formosus also is found in Northern Mexico. (Brylski, 1999; Guinn, 2002)


Chaetodipus formosus occupies a wide variety of elevations, from 85 m below sea level to 1,970 meters above. They are most often found in rocky desert areas that contain sagebrush, desert scrub, and desert succulent shrubs with hard groundcover and/or rocky soils. These areas are often at the base of cliffs or at the mouth of canyons. They are found in the lava beds of Vulcan's Throne, on rocky or gravelly soil of dry stream beds, or among marble-sized rocks of the desert scrub floor and Colorado River beaches. (Brylski, 1999; Guinn, 2002; "Long-tailed pocket mouse", 2004)

  • Range elevation
    -85 to 1,970 m
    -278.87 to ft

Physical Description

Body length of these animals is between 76 and 101 mm, with a crested tail usually adding 80 to 110 mm in length. They weigh between 10.5 and 17 grams. The dorsal pelage is grey with a white underside. Chaetodipus formosus has the same dental formula as all heteromyids: I 1/1, C 0/0, P 1/1, M 3/3 X 2 = 20 (Brylski, 1999; "Long-tailed pocket mouse", 2004)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    10.5 to 17.0 g
    0.37 to 0.60 oz
  • Range length
    76 to 101 mm
    2.99 to 3.98 in
  • Average basal metabolic rate
    0.103 W


The is no information found on the mating systems of long-tailed pocket mice (Brylski, 1999; Guinn, 2002)

Chaetodipus formosus is an iteroparous species breeding more than once in its life time. The breeding season occurs in the spring lasting about four months with a peak in the middle two months. Populations can increase rapidly, and under good conditions up to 70 per cent of the females in the population will become pregnant. With an average litter size just under 6 young, this can lead to up to a five fold increase in population size. In years with good precipitation and food suppy a second breeding season may occur, and those young born early in the year are able to reproduce by this second season. (Brylski, 1999; Geluso, 1999; Guinn, 2002)

  • Breeding interval
    These animals usually produce one litter per year, but can produce two if the conditions are good.
  • Breeding season
    Breeding season for these mice is from April to July.
  • Range number of offspring
    2 to 7
  • Average number of offspring
  • Average number of offspring
  • Average gestation period
    28 days
  • Range age at sexual or reproductive maturity (female)
    10 to 12 months
  • Range age at sexual or reproductive maturity (male)
    10 to 12 months

There is no information on the parental care of C. formosus. However, most small mice are altricial when they are born. Mothers typically care for the young in a nest of some sort until they are able to walk about. Most parental care in mice is provided by females, who groom, nurse, and protect the young. No information is available on the extent of male parental care in this species.

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


No information could be found on the lifespan of long-tailed pocket mice, but generally pocket mice only live 1 to 2 years.

  • Range lifespan
    Status: wild
    5 (high) years


Distribution and abundance seem to depend on soil characteristics rather than on characteristics of the shrub cover. Long-tailed pocket mice are found a variety of desert shrub species which provide sparse to dense cover for the mice. They are nocturnal, active on the surface throughout much of the year with exception of late fall through early spring. Below-ground activity and aestivation is related to periods of cold weather, with increasing above-ground ambient temperatures accompanied by increasing activity. In summer, 30 to 40% of time is spent above-ground Daily cycles involve bursts of activity shortly after sunset for 2 hr followed by a cessation of activity at 6 hr after sunset. Burrows are excavated in gravelly or rocky banks, or at base of shrubs. The species is solitary, and aggressively maintains a territory. Competition for food has also been documented. (Brylski, 1999; Geluso, 1999; Price, et al., 2002)

Home Range

Males have larger home range than females, and range size is inversely related to population density. In the Mojave desert, the average size of the home range was 0.55 hectares. (Brylski, 1999)

Communication and Perception

No information could be found on the communication techniques of C. formosus. However, as mammals, they are able to perceive visual stimuli, and have senses of smell and taste. It is likely that these senses are involved in communication. Tactile communication is probably important between mates, rivals, or between mother and offspring.

Food Habits

Chaetodipus formosus has external fur lined cheek pouches to carry seed and other food items. Seed caching and food storage is common among the family Heteromyidae. Although this species is primarily granivorous, they also eat fruits and arthropods, and feed opportunistically on stems and leaves of green vegetation. Seeds are collected on the ground beneath and between shrubs, and on rocky surfaces. Water is obtained from food, especially green vegetation. (Brylski, 1999; Guinn, 2002; Jenkins and Breck, 1998)

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


Predators include owls, snakes, leopard lizards, swift foxes, and other predatory mammals. (Brylski, 1999)

Ecosystem Roles

Burrows are excavated in gravely or rocky banks, or at the base of shrubs. This provides aeration of the soil because they are burrowing and turning up the soil. As seed cachers, they probably help to disperse seeds. Because they are a prey species, it is likely they could affect predator populations--especially in years where reproduction is high. (Brylski, 1999)

Commensal/Parasitic Species
  • 10 species of mite, 3 flea species and 3 tick species use this pocket mouse as a host.

Economic Importance for Humans: Positive

No information was found on positive economic impacts of long-tailed pocket mice.

Economic Importance for Humans: Negative

Burrowing could be a potential conflict for farmers if the species is creating burrows in farm fields. Heteromyid rodents are also reservoirs for many zoonotic diseases. (Brylski, 1999)

Conservation Status

Long-tailed pocket mice are not listed by IUCN or CITES.

Other Comments

Until recently, this species was refered to as Perognathus. Hafner suggested that, based on morphological and other characters, spiny perognathine pocket mice merited the elevation of the subgenus Chaetodipus to full generic status. (Hafner, 1983)


Nancy Shefferly (editor), Animal Diversity Web.

Amanda Eckhart (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor), University of Wisconsin-Stevens Point.



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.

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.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


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.


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.


union of egg and spermatozoan


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


an animal that mainly eats seeds


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


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.

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

soil aeration

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


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.


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.


The New Mexico Department of Game & Fish. 2004. "Long-tailed pocket mouse" (On-line). Biota Information System Of New Mexico. Accessed March 29, 2004 at

Brylski, P. 1999. "Long tailed Pocket Mouse" (On-line). California Wildlife Habitat Relationships System. Accessed March 29, 2004 at

Geluso, K. 1999. Long-tailed pocket mouse (Chaetodipus formosus). Pp. 511-512 in D Wilson, S Ruff, eds. The Smithsonian Book of North American Mammals. Washington, D.C.: Smithsonian Institution Press.

Guinn, E. 2002. "Long-tailed pocket mouse" (On-line). Utah Division of Wildlife Resources. Accessed March 29, 2004 at

Hafner, J. 1983. Evolutionary Relationships of Heteromyid Rodents. Great Basin Naturalist Memoirs, 7: 3-29.

Jenkins, S., S. Breck. 1998. Differences in Food Hoarding Among Six Species Of Heteromyid Rodents. Journal of Mammalogy, 79: 1221-1232.

Price, M., N. Waser, S. McDonald. 2002. Seed Caching By Heteromyid Rodents From Two Communities: Implications for Coexistence. Journal of Mammalogy, 81: 97-106.