Notiosorex crawfordi (Desert Shrew) 

Written by Rachel Spruance (Mammalogy Lab--Fall 2003)

Edited by Karah Gallagher and Jennifer Bailey

Map prepared by Greg T. Lewellen

The desert shrew, Notiosorex crawfordi, is found throughout a broad range of the southwestern and south-central United States and central Mexico (Armstrong and Jones 1972).  Individuals have been captured in the states of Arkansas, Arizona, California, Colorado, Oklahoma, Nevada, New Mexico, Texas, and Utah (Armstrong and Jones 1972).  N. crawfordi has also been documented on San Martin Island, a small volcanic island off the coast of Baja California, Mexico (Schulz et al. 1970).  In Texas, this species has been documented in Archer, Baylor, Bee, Bexar, Brewster, Briscoe, Coke, Cottle, Crosby, Duval, El Paso, Garza, Hidalgo, Howard, Jeff Davis, Kerr, Lubbock, Maverick, Medina, Moore, Motley, Nueces, Refugio, Sutton, Wichita, Wilbarger, and Zavala counties (Davis and Schmidly 1994).  Counties in other states in which the genus Notiosorex has been documented include Coconino and Cochise counties of Arizona (Armstrong and Jones 1972); Ventura, Los Angeles, San Bernardino, Imperial, and San Diego counties of California (Armstrong and Jones 1972); Nye and Clark counties of Nevada (Bradley and Moor 1968); and Lincoln and Valencia counties of New Mexico(Fisher 1941).

Photo by R. Matlack

Physical Characteristics:

Like all shrews, N. crawfordi is a small animal, their external measurements ranging from 93.2-25.5-11.9-7.7 for males and 92.0-22.0-11.0-8.0 for females (Armstrong and Jones 1972).  A documented measurement for a subadult specimen is 73.0-28.0-9.5-5.0 (Carothers 1968).   An average adult weight for this animal may range from 3.1 grams to 5.2 grams (Carothers 1968).  The dental formula for N. crawfordi is i 3/2, c 1/0, p 1/1, m 3/3, total 28 (Davis and Schmidly 1994).  Cranial measurements of a specimen taken in Briscoe County, Texas are: Length of skull, 17.0; palatal length, 7.5; greatest length of mandible,10.0; cranial breadth, 8.3; interorbital breadth, 3.9; maxillary breadth, 5.3 (Davis 1941).  The teeth of N. crawfordi are somewhat pigmented. 

 Coloration of the pelage has been described as silvery, brownish-gray, and lead-gray (Hoffmeister and Goodpaster 1962).  Light underparts, noticeable vibrissae, and conspicuous pinnae are also characteristics of this species (Armstrong and Jones 1972).  Males are often marked by well developed lateral skin glands (Hoffmeister and Goodpaster 1962).  It has also been observed that juvenile pelage differs from that of the adults by being generally shorter, sparser, and lighter in color (Hoffmeister and Goodpaster 1962)

Natural History:

Food Habits: As members of Insectivora, desert shrews consume primarily insects and related arthropods.  In captivity, N. crawfordi has been observed to eat Carabidae beetles, earwigs, sowbugs, crickets, cockroaches, moths, and beetle larvae (Huey 1936).  This species apparently has a distaste for earthworms, caterpillars, and scorpions- all have been consistently refused by captive animals (Huey 1936).   N. crawfordi is also known to eat carrion of small birds, mammals, and reptiles and to participate in coprophagy (Cunningham 1956).  Stomach content of a male shrew was 35% unidentifiable insects and 65% termites. The stomach content of a female shrew was 5% vegetation, 10% beetle larvae, 15% duck feathers, 30% termites, and 40% adult beetles (Bradley and Moor 1968).  N. crawfordi has also been found in abandoned bee hives feeding on the larvae of the bee moth (Willet 1939).

Reproduction: Little is known regarding the reproductive habits of N. crawfordi.  The breeding season apparently runs from April to late November, but this may show both temporal and spatial variation (Baker and Spencer 1965).  In Arizona and California, studies indicate that young are born in both early and late summer (Hoffmeister and Goodpaster 1962).  It remains unknown whether female N. crawfordi is monestrous or polyestrous, as well as information regarding the gestation length and embryological development (Armstrong and Jones 1972).  Litter size is usually from 3-5 young (Davis and Schmidly 1994).

Behavior: N. crawfordi has been described as a deep-sleeping species that is active during various periods of both day and night (Hoffmeister and Goodpaster 1962).  This species exhibits movements that are consistently rapid and direct, and this is easily observed in its foraging habits (Huey 1936).  N. crawfordi normally dispatch their insect prey by crushing the head with their teeth; overly large or fast prey may be stalled by removing the legs, and then killed (Huey 1936).  These prey items may be consumed immediately, or placed in a food cache.   Members of N. crawfordi are atypical shrews in that they may co-habitate peacefully (Hoffmeister and Goodpaster 1962). 

It is also of note that N. crawfordi does not appear to construct burrows or runways, instead it appears that they live in close association with wood rats of the genus Neotoma, and utilize the middens of this animal (Davis 1941).  It has also been suggested that N. crawfordi makes use of the burrows and runways of Peromyscus, Dipodomys, and Reithrodontomys (Coulombe and Banta 1964).  Both male and female members of N. crawfordi are known to construct nests made of available materials (Hoffmeister and Goodpaster 1962).

Habitat: N. crawfordi is associated with various xeric habitats throughout its range and has been found from very near sea level to altitudes approaching 6500 feet (Lindeborg 1960).  Areas of Colorado exhibiting mesic-boreal conditions, particularly those of the Roan Plateau and the White River Plateau, may form a barrier to its spread beyond the Colorado River drainage (Caire and Finley 1977).  Plentiful ground litter and abundant insect prey appear to be a determining factor for ideal habitat (Bradley and Moor 1968).  Some documented habitats of this shrew are agave-grassland, mesquite-cactus, creosote- and salt-bush, desert sagebrush, lower edge of piñon-juniper, lower edge oak-mimosa, and yucca-cactus (Hoffmeister and Goodpaster 1962).   

These habitats are also grouped into categories such as both the Upper and Lower Sonoran life zones, and transition zones between different areas such as that between the Great Basin steppe and the Mojave Desert (Coulombe and Banta 1964).  The general appearance of common habitat may be described as having loose, sandy soil that is covered by small rocks and a varying growth of shrubs and other xeric-adapted plants (Fisher 1941). 

 Some seemingly incongruous habitats have also been recorded; N. crawfordi has been captured in both riparian and alkaline marsh habitat, and in areas of relatively high human activity such as agricultural fields and stables (Fisher 1941). Entire carcasses have been found in a cave in New Mexico (Jones 1959).   In the more inhospitable environments, it is noted that N. crawfordi makes use of milder microclimates for its nest site (Coulombe and Banta 1964).

N. crawfordi is of little or no economic importance independently, but it has been cited as an indicator species of Lower Sonoran conditions and so may consequently be viewed as a desirable species to conserve and maintain (Ingles 1954).  Remains of this animal have been frequently documented in owl pellets and predators including coatis, bobcats, various species of skunks, and several raptors share its habitat and may rely partially on the shrew’s existence for their own survival (Durham 1955).

Conservation Status:

As of 2003, there is no information regarding the conservation status of N. crawfordi.

References:

Armstrong, D.M. and J.K. Jones, Jr. 1972. Notiosorex crawfordi. Mammalian species 17:1-5.     

Baker, R.J. and D.L. Spencer. 1965. Late fall reproduction in the desert shrew.  Journal of Mammalogy 46:330.

Bradley, W.G. and K.S. Moor. 1968. Additional records of Notiosorex crwafordi for southern Nevada.  Southwestern Naturalist 13:104-105.

Caire, W. and R.B. Finley, Jr. 1977. The desert shrew, Notiosorex crawfordi (Coves), from Northwestern Colorado. Southwestern Naturalist 22:284-285.

Carothers, S.W. 1968. Additional records of Notiosorex c. crawfordi in Arizona. Southwestern Naturalist 13:449.

Coues, E.1877. Precursory notes on American insectivorous mammals, with descriptions of new species. Bulliten of United States Geology and Geography Survey of Territories 3:631-653.

Coulombe, H.N. and B.H. Banta. 1964. The distribution and ecology of the Crawford desert shrew, Notiosorex crwafordi, in Saline Valley, Inyo County, California. Wasmann Journal of Biology 22:277-297.

Cunningham, J.D. 1956. Ecology and occurrence of Notiosorex in Southern California. Journal of Mammalogy 37:108-110.

Davis, W.B. 1941. Additional records of Notiosorex crawfordi from Texas. Journal of Mammalogy 22:319-320.

Davis, W.B., and D.J. Schmidly. 1994. The Mammals of Texas. University of Texas Press, Austin.

Durham, F.E. 1955. The gray shrew, Notiosorex crawfordi, in Los Angeles County, California. Journal of Mammalogy 36:561-562.

Fisher, H.I. 1941. Notes on shrews of the genus Notiosorex. Journal of Mammalogy 22:263-269.

Hoffmeister, D.F. and W.W. Goodpaster. 1962. Life history of the desert shrew, Notiosorex crawfordi. Southwestern Naturalist 7:236-252.

Huey, L.M. 1936. Some habits of a gray shrew in captivity. Journal of Mammalogy      17:143-145.

Ingles, L.G. 1954. Mammals of California and its coastal waters. Stanford University Press, Stanford, Connecticut.

Jones, J.K. Jr. 1959. A third locality for the desert shrew, Notiosorex crawfordi, in New Mexico. Southwestern Naturalist 4:111-112.

Lindeborg, R.G. 1960. The desert shrew, Notiosorex crawfordi, in San Miguel County, New Mexico. Southwestern Naturalist 5:108-109.

Schulz, T.A. et al. 1970. First insular record of Notiosorex crawfordi, with notes on other mammals of San Martin Island, Baja California, Mexico. Journal of Mammalogy 51:148-150.

Willet, G. 1939. An extension of the known range of Notiosorex crawfordi. Journal of Mammalogy 20:102.