Chaetodipus nelsoni
Nelson's pocket mouse

Chaetodipus nelsoni is found in the Chihuahuan Desert of the Mexican Plateau from southeastern New Mexico, to western Texas, to Jalisco Mexico. (Best, 1994; Lee, 1990)

Chaetodipus nelsoni occupies upper and lower Sonoran life zones at 365 to 2,025 m elevation. Habitat between the desert shrub vegetation and pine-oak-juniper woodland zones is preferred. In Durango, the Rio Nazas canyon is a barrier for some species of small mammals, but does not seem to be for C. nelsoni. Steep rocky slopes, sandy flats, and around rock piles and old stone buildings are common habitats for this species. Chaetodipus nelsoni seems to avoid sandy washes. (Best, 1994; Schmidly, 1999)

Chaetodipus nelsoni is a long and slim pocket mouse of medium-size. The species is known for having a long crescent tail, external fur-lined cheek pouches, and dark spines on the rump. Spines can best be seen by pressing down the rump skin forcing the spines to stick up. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

The ears of Nelson's pocket mice are small and oval. The tail is longer than the head and body. It is sparsely haired at the base, and the terminal half is crested, penicillate, and darker dorsally than ventrally. The front feet are smaller than the hind feet, and all soles are dark. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

The pelage is brown on the back and sides, whitish on the belly, and long on the middorsal region. Summer pelage is coarse and dorsally yellowish-brown from a combination of coarse buffy and black hairs. Winter pelage is finer and grayish black. In Texas, pelage is palest in April and increasingly gets darker until September. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

Males of this species are slightly larger than females. There is also significant geographic variation in size in this species. In general, animals in the north are larger than those in the south. In the southern portion of the species range, males average 14.7 g (12.0 to 16.5 g) and females 13.8 g (12.5 to 15.5g). In the northern portion of the range, males average 18.5 g (17.0 to 20.0g) and females 17.0 g (15.0 to 18.0). In Texas, males average 16.1 g and females 14.4 g (no ranges available). (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

Total length of males and females averages about 180 mm; hind foot length is 21 mm; ear length 8 mm. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

Chaetodipus nelsoni is sympatric and parapatric with other Chaetodipus species. Chaetodipus nelsoni is generally larger in size, and has more noticeable rump spines than other members of the genus. Also, the distal ends of the rump spins are dark ventrally and pale dorsally. There are no elongate rump hairs, and soles of hind feet are dark. (Best, 1994)

Characteristic rump spines may not be prominent in young and molting individuals. Young C. nelsoni hind feet have white subauricular spots and dusky plantar surfaces compared to other species. (Best, 1994)

In the Big Bend region of Texas, 25% of subadults and 12% of adults survive from July to July. Based on trapping studies, individual were able to survive in the wild for more than 30 months, although the average life span was obviously less than that. Annual turnover in the population is about 86%. (Best, 1994; Texas Tech university, 1997)

Nelson's pocket mice are nocturnal, leaving the burrow after dusk. Locomotion is typically slow and uses all four feet, except when an animal is frightened. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

Burrows are dug at the bases of usually thorny desert shrubs. Chaetodipus nelsoni rarely wanders far from cover of bushes or rock. (Best, 1994; Schmidly, 1999; Texas Tech university, 1997)

Unlike other Chaetodipus species, C. nelsoni is active year round. This species does not go into torpor nor hibernate. It is less active in winter and early spring compared to other times of the year. (Best, 1994; Texas Tech university, 1997)

These pocket mice undergo one annual molt, between May and October, which typically lasts less than a month. Molt starts at the nose and finishes at the ankle. The ventral side typically molts slower and lacks a molt line. The ventral molt is confined to the belly region, while the dorsal line reaches the rump. A molt line extending from the rump laterally and anteriorly across the thighs and sides defines the final stage of molt. Finally, the molt line advances posteriorly on the belly and down the hind legs to the ankles. Subadults complete the post-juvenile molt by September. (Best, 1994)

Home Range

Male nelson's pocket mice have home ranges of aproximately 0.14 to 0.45 ha. These ranges overlap when population densities are high, and are complimentary when population densities are low (July and September). Female home ranges tend to be somewhat smaller than those of males, and usually do not overlap, if there is overlap it occurs in July, December, and May. (Best, 1994)

Communication in this species has not been reported on in the literature. However, as mammals, these creatures are likely to use some combination of visual, accoustic, tactile, and chemical communication.

Nelson's pocket mice feed almost entirely on seeds of various desert shrubs and grasses. They also eat insects and other parts of plants. Food is transported in external cheek pouches and stored in chambers of the burrow system. (Best, 1994; Schmidly, 1999)

The main predators of C. nelsoni are the western diamondback rattlesnakes, great horned owls, and barn owls. Ectoparasites include chiggers. (Best, 1994)

In Durango, dark volacnic soils around the Guadiana lava fields are common. The C. nelsoni here has a distinctly blackish back and buffy colored bellies. Individuals from center of lava fields are darker than those from the outer edges of the lava fields. Individuals in adjacent pale soils are lighter in color. These differences in coloration with habitat are apparently related to decreasing the visibility of these mice. (Best, 1994)

Nelson's pocket mice play a role in seed dispersal of desert vegetation. They act as a food base for owls and snakes. The burrowing behavior of this species may help aerate soils. (Best, 1994)

Nelson's pocket mouse may be considered a house pest since it prefers to live near old stone buildings, this may be a problem in occupied buildings. Also, there is potential for a pest status since it is a granivore, it may get into feed storage areas.

Nelson's pocket mouse's seed dispersal may distribute native vegetation leading to more natural habitat. Also, the seed dispersal may lead to more vegetation for grazing livestock. (Best, 1994)

Chaetodipus nelsoni is considered to be a good indicator species for Chihuahuan desert grasslands. Populations are abundant within the home range and there are no current conservation issues concerning C. nelsoni. Chaetodipus nelsoni is listed by CITES nor by IUCN. This species is often the most abundant desert mammal within its range, especially in late August and September. (Best, 1994; CITES, 12/2/02; IUCN, 2002)

Fossil history of Perognathinae begins in the Miocene. Possible close remains have been found in late Pleistocene deposits from Cueva Quebrada, Val Verdo Co., Texas. In central Coahuila recent remains have been found in a cave. (Best, 1994)

An interesting fact about C. nelsoni is that the hind feet are 30% of the length of the head and body. (Best, 1994)