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.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Southern North America. From central Baja California, Mexico, north through southeastern California, northwestern Arizona, Nevada, and western Utah. To elevations of 8000 ft.

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

Range mass: 10.5 to 17.0 g.

Range length: 76 to 101 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 0.103 W.

Length: 21 cm

Weight: 24 grams

• Terrestrial

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.

Range elevation: -85 to 1,970 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: desert or dune

Comments: Gravelly ground; often inhabits rocky desert slopes and canyons. Sleeping and birthing occur in underground burrows.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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.

Animal Foods: insects; terrestrial non-insect arthropods

Plant Foods: leaves; seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: herbivore (Granivore )

Comments: Feeds mainly on seeds, but may also eat some green vegeta- tion and insects. Food is stored in underground storage chamber within burrow system.

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.

Ecosystem Impact: disperses seeds; soil aeration

Commensal/Parasitic Species:

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

Predators include owls, snakes, leopard lizards, swift foxes, and other predatory mammals.

Known Predators:

• owls (Strigiformes)
• swift foxes (Vulpes velox)

Primarily solitary. Populations probably fluctuate seasonally and year to year. In Nevada, population density was 0.04-1.3 per ha. Home ranges were estimated at 0.8 ha for females and 2.4 ha for males (Bureau of Land Management, no date).

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.

Perception Channels: visual ; acoustic

Comments: Remains in underground burrow during the winter (alternate periods of dormancy & activity, depending on weather). Periods of surface activity increase gradually in spring. In summer individuals spend 30-40% of their time above ground.

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.

The is no information found on the mating systems of long-tailed pocket mice

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.

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: 6.

Range age at sexual or reproductive maturity (female): 10 to 12 months.

Range age at sexual or reproductive maturity (male): 10 to 12 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 1 g.

Average gestation period: 28 days.

Average number of offspring: 5.

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)

In Nevada, breeding season may extend from March to September, usually ends in May. Average litter size is about 5.6 (Bureau of Land Management, no date. Young are born in May-June. May not reproduce in years of low precipitation (Kenagy and Bartholomew 1985).

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

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

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.

Negative Impacts: injures humans (carries human disease); crop pest; causes or carries domestic animal disease

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

Comments: This species formerly was included in the genus Perognathus. Subgenus Chaetodipus was elevated to full genus status by Hafner and Hafner (1983); this treatment was supported by a phylogenetic analysis of Heteromyidae based on myology (Ryan 1989). Chaetodipus was accepted as a full genus by Jones et al. (1992), Patton (in Wilson and Reeder 1993, 2005), and most other authors subsequent to Hafner and Hafner (1983). In a phylogeny based on molecular data, Riddle (1995) found support for the monophyly of Chaetodipus, including C. formosus, relative to Perognathus.