Chaetodipus formosus
long-tailed pocket mouse

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; The New Mexico Department of Game and Fish, 2004)

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; The New Mexico Department of Game and Fish, 2004)

No information could be found on the lifespan of long-tailed pocket mice, but generally pocket mice only live 1 to 2 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, Waser, and McDonald, 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)

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.

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)

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

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)

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)

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

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

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)