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; "Nelson's Pocket Mouse", 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; "Nelson's Pocket Mouse", 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; "Nelson's Pocket Mouse", 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; "Nelson's Pocket Mouse", 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)
The length of the breeding season is approximately 5 months. In Texas, breeding begins in February and the peak of pregnancy is reached in March. Average litter size is about three, with a range of one to five young. This species has a gestation period of 30 days. Young grow rapidly and leave the nest in approximately four weeks. The annual turnover in the population is about 86%. (Best, 1994; "Nelson's Pocket Mouse", 1997)
Nests are located in the burrows, and consist of shredded grasses. (Best, 1994)
Members of this species appear to reach reproductive maturity quite young. Females still having subadult pelage were often found to be pregnant or to have placental scars, indicating that they had previously had a litter. Males reach sexual maturity before they reach adult size. (Best, 1994)
Details on the parental behavior of this species have not been recorded. As in all mammals, the female cares for the young, providing them with milk, grooming, and protection. The young are probably altricial, and they do not leave the nest for about four weeks. Male parental behavior has not been reported in these animals. (Best, 1994; Schmidly, 1999; "Nelson's Pocket Mouse", 1997)
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; "Nelson's Pocket Mouse", 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. (Schmidly, 1999; Schmidly, 1999; Best, 1994; Schmidly, 1999; "Nelson's Pocket Mouse", 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; "Nelson's Pocket Mouse", 1997; Best, 1994; Schmidly, 1999; "Nelson's Pocket Mouse", 1997; Best, 1994; Schmidly, 1999; "Nelson's Pocket Mouse", 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; "Nelson's Pocket Mouse", 1997; Best, 1994; "Nelson's Pocket Mouse", 1997; Best, 1994; "Nelson's Pocket Mouse", 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; Best, 1994; Best, 1994)
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)
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'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)
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.
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-listed species database", 12/2/02; "2002 IUCN Redlist of Threatened Species", 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)
Nancy Shefferly (editor), Animal Diversity Web.
Mandi Huntington (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), 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.
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.
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.
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.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
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.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
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
digs and breaks up soil so air and water can get in
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.
American Society of Mammalogists. 1999. The Smithsonian Book of North American Mammals. Washington D.C.: The Smithsonian Institute.
IUCN. 2002. "2002 IUCN Redlist of Threatened Species" (On-line ). Accessed 12/4/02 at http://www.redlist.org/.
CITES. 12/2/02. "CITES-listed species database" (On-line ). CITES. Accessed 12/4/02 at http://www.cites.org/eng/resources/species.html.
New Mexico Fish and Game. 2000. "Nelson's Pocket Mouse" (On-line ). Biota Information System Of New Mexico BISON. Accessed 10/3/02 at http://www.fw.vt.edu/fishex/nmex_main/species/050450.htm.
Texas Tech university. 1997. "Nelson's Pocket Mouse" (On-line ). The Mammals of Texas- Online Edition. Accessed 10/3/02 at http://www.nsrl.ttu.edu/tmot1/chaenels.htm.
Best, T. 1994. Chaetodipus nelsoni. Mammalian Species, 484: "1-6". Accessed 10/3/02 at http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-484-01-0001.pdf.
Lee, T. 1990. Geographic Distribution of the Cytotypes of *Chaetodipus nesloni*. The Southwestern Naturalist, 35/4: "454-455".
Schmidly, D. 1999. Nelson's Pocket Mouse (Chaetodipus nelsoni). Pp. 515-516 in D Wilson, S Ruff, eds. The Smithsonian Book of North American Mammals. Washington and London: The Smithsonian Institution Press.