Sigmodon ochrognathus - V. Bailey, 1902
Yellow-nosed Cotton Rat
Taxonomic Status: Accepted
Related ITIS Name(s): Sigmodon ochrognathus V. Bailey, 1902 (TSN 180350)
Spanish Common Names: Una Rata Algodonera
Unique Identifier: ELEMENT_GLOBAL.2.100939
Element Code: AMAFF07040
Informal Taxonomy: Animals, Vertebrates - Mammals - Rodents
Kingdom Phylum Class Order Family Genus
Animalia Craniata Mammalia Rodentia Cricetidae Sigmodon
Genus Size: C - Small genus (6-20 species)
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Concept Reference
Concept Reference: Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at:
Concept Reference Code: B93WIL01NAUS
Name Used in Concept Reference: Sigmodon ochrognathus
Conservation Status

NatureServe Status

Global Status: G4G5
Global Status Last Reviewed: 11Aug1998
Global Status Last Changed: 11Aug1998
Rounded Global Status: G4 - Apparently Secure
Reasons: Moderately widespread in the southwestern United States and northwestern Mexico; occurrences estimated at 101+; possibly declining, but no specific information; U.S. populations moderately threatened by habitat elimination and degradation.
Nation: United States
National Status: N3N4 (15Jan1997)

U.S. & Canada State/Province Status
United States Arizona (S4), New Mexico (S2), Texas (S3)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 20,000-2,500,000 square km (about 8000-1,000,000 square miles)
Range Extent Comments: Southeastern Arizona, extreme southwestern New Mexico, and southwestern Texas south to Durango, Mexico, from 915 to 2,593 meters (Arizona Game and Fish Department 1997). In Arizona, bounded by the Boboquivari, Santa Rita, and Santa Catalina mountains to the northwest, the Galiuro Mountains to the north, and the Chiricahua Mountains to the east (Arizona Game and Fish Department 1997). Limited in New Mexico to Hidalgo County and (New Mexico Department of Game and Fish 1997) and in Texas to Jeff Davis, Presidio, and Brewster counties. The Mexican distribution includes northern Durango, western Coahuila, Chihuahua, and northeastern Sonora (Rappole and Tipton 1987).

Number of Occurrences: 81 to >300
Number of Occurrences Comments: No information is available from Mexico, and United Sates information varies from specific to general. The Arizona Natural Heritage Program has recorded 32 extant occurrences and has assigned a rank of S3S4, usually 21-100 or over 100 occurrences (Sabra Schwartz, pers. comm., 1998). Frey (pers. comm., 1998) stated that there may be more than 101 populations in Arizona and New Mexico. Schmidley (1977) mapped 12 collection sites in Texas. The Texas Heritage Program has not recorded occurrences, but has applied a state rank of S3, typically 21-100 occurrences. Ranked S2 by the New Mexico Heritage Program, typically 6-20 occurrences.

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Specific abundance information is not available. However, population numbers in Arizona and New Mexico are estimated at over 10,000 individuals or over 50,000 acres (Jennifer Frey, pers. comm., 1998). Listed as rare and local in the Chihuahua region of Mexico (Findley and Caire 1977). According to Schmidly (1977), relatively common in Big Bend National Park and the Davis Mountian region of Texas, but rare in Sierra Viejo. In Texas, the peritage program made a rough estimate of 5,000 individuals (Mark Gallyoun, pers. comm., 1998).

Overall Threat Impact Comments: Threatened by habitat elimination and degradation due to overgrazing or other factors reducing or eliminating native perennial grass (Arizona Game and Fish Department 1997; Jennifer Frey, pers. comm., 1998). In Texas, grassland habitats have been degraded through altered fire regimes and increased urbanization (Mark Galyoun, pers. comm., 1998). The degree of threat to United States populations is considered moderate (Mark Galyoun and Jennifer Frey, pers. comm., 1998).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Information on population trends is limited to general and contradictory statements regarding United States populations. The Texas Heritage Program regards populations there are stable (Mark Gallyoun, pers. comm., 1998). According to Frey (pers. comm., 1998), maybe declining in Arizona and New Mexico. However, Dobson and Murie (1987) stated that collection records indicate a northward expansion has occurred in Arizona and New Mexico during the past 50 years and is continuing today. Davis and Ward (1988) described an apparent colonization of a new grassland on a mountain top in southeastern Arizona.

Other NatureServe Conservation Status Information

Inventory Needs: Obtain rangewide information on population numbers and abundance. Monitor populations to determine trends. Determine extent and effect of threats.

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Southeastern Arizona, extreme southwestern New Mexico, and southwestern Texas south to Durango, Mexico, from 915 to 2,593 meters (Arizona Game and Fish Department 1997). In Arizona, bounded by the Boboquivari, Santa Rita, and Santa Catalina mountains to the northwest, the Galiuro Mountains to the north, and the Chiricahua Mountains to the east (Arizona Game and Fish Department 1997). Limited in New Mexico to Hidalgo County and (New Mexico Department of Game and Fish 1997) and in Texas to Jeff Davis, Presidio, and Brewster counties. The Mexican distribution includes northern Durango, western Coahuila, Chihuahua, and northeastern Sonora (Rappole and Tipton 1987).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AZ, NM, TX

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at

Range Map Compilers: Sechrest, 2002

U.S. Distribution by County Help
State County Name (FIPS Code)
AZ Cochise (04003), Graham (04009)*, Pima (04019), Santa Cruz (04023)
NM Hidalgo (35023)*
TX Brewster (48043), Culberson (48109), Jeff Davis (48243), Presidio (48377)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
13 Playas Lake (13030201)+*, Cibolo-Red Light (13040201)+*, Black Hills-Fresno (13040203)+, Maravillas (13040206)+, Santiago Draw (13040207)+, Salt Basin (13050004)+*, Delaware (13070002)+, Barrilla Draw (13070005)+
15 Animas Valley (15040003)+*, San Simon (15040006)+, Willcox Playa (15050201)+, Upper San Pedro (15050202)+, Lower San Pedro (15050203)+, Upper Santa Cruz (15050301)+, Rillito (15050302)+, Lower Santa Cruz (15050303)+, Brawley Wash (15050304)+*, San Simon Wash (15080101)+*, Rio De La Concepcion (15080200)+*, Whitewater Draw (15080301)+, San Bernardino Valley (15080302)+*, Cloverdale (15080303)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A cotton rat.
Reproduction Comments: Undoubtedly produces multiple litters annually. Gestation lasts probably 33-36 days. Litter size is 2-6. Females less than 2 months old may breed (Hoffmeister 1986).
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Terrestrial Habitat(s): Cropland/hedgerow, Desert, Grassland/herbaceous, Woodland - Conifer, Woodland - Mixed
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Dry rocky slopes in oak-pinyon-juniper habitat, montane meadows in ponderosa pine and Douglas-fir forests, rocky slopes of desert mountains with scattered bunches of grass, and grassy montane flats with deep soils, few rocks (in areas where it is the only cotton rat present). May nest underground or in or under clump of grass or agave (Davis and Sidner, in Wilson and Ruff 1999; Hoffmeister 1986).
Adult Food Habits: Herbivore
Immature Food Habits: Herbivore
Food Comments: Feeds primarily on vegetable matter. Does not store food.
Adult Phenology: Circadian
Immature Phenology: Circadian
Length: 26 centimeters
Weight: 112 grams
Economic Attributes Not yet assessed
Management Summary Not yet assessed
Population/Occurrence Delineation
Group Name: Small Murid Rodents

Use Class: Not applicable
Minimum Criteria for an Occurrence: Evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in appropriate habitat where the species is presumed to be established and breeding.
Mapping Guidance: Separate sites separated by less than 1000 meters should be mapped as separate polygons.
Separation Barriers: Barriers include: wide highways with heavy traffic (subjective determination) and highways with continuous solid barriers that prevent rodent passage; major water bodies, arbitrarily set at those greater than 50 meters across in ice-free areas and those greater than 200 meters wide if frozen regularly.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Home ranges may be quite small, but at least some species exhibit good dispersal ability that may take them several kilometers from their natal area (Maier 2002). Peromyscus that have been displaced up to 3 km may return home within a few days (see Maier 2002). Displaced Neotoma fuscipes dispersed up to at least 1.6 km from their release point in five nights (Smith 1965). A male Dicrostonyx richardsoni moved more than 3 kilometers per day several times (Engstrom, in Wilson and Ruff 1999). Some species can traverse significant distances of unsuitable habitat. For example, Peromyscus leucopus may move between wooded areas separated by a deforested agricultural gap of up to at least 2 km (Krohne and Hoch 1999). In New Brunswick, a tagged subadult male Peromyscus maniculatus was captured at locations 1.77 km apart after a period of 2 weeks in September, suggesting that dispersal may extend at least this far (Bowman et al. 1999). In Kansas, individual Peromyscus maniculatus were captured at trap sites up to 1.32 km apart (Rehmeier et al. 2004). Dispersal can play a key role in the population dynamics of murid rodents.

Patterns of genetic (DNA) variation indicate that gene flow can be low among subpopulations of Neotoma magister and that effective dispersal is limited among subpopulations separated by as little as 3 km (Castleberry et al. 2002).

Separation distance for suitable habitat is a compromise between the typical small home range sizes of these mammals and their sometimes considerable dispersal ability and the likely low probability that two occupied locations separated by less than several kilometers of suitable habitat would represent independent populations.

Roads, especially divided highways, are major barriers to dispersal in small mammals (Oxley et al. 1974, Wilkins 1982, Garland and Bradley 1984).

Date: 08Mar2005
Author: Hammerson, G., and S. Cannings
Notes: Group contains most members of the family Muridae: mice, voles, lemmings, woodrats, etc.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 11Aug1998
NatureServe Conservation Status Factors Author: Clausen, M. K.
Element Ecology & Life History Edition Date: 14Apr1993
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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  • Baker, R. H. 1956. Mammals of Coahuila, Mexico. Univ. of Kansas Publications, Mus. of Nat. Hist. 9(7):125-335.

  • Baker, R. H., and K. A. Shump 1978. SIGMODON OCHROGNATHUS. Mammalian species, 97:1-2.

  • Banks, E. M., R. J. Brooks, and J. Schnell. 1975. A radiotracking study of home range and activity of the brown lemming (Lemmus trimucronatus). Journal of Mammalogy 56:888-901.

  • Bowman, J. C., M. Edwards, L. S. Sheppard, and G. J. Forbes. 1999. Record distance for a non-homing movement by a deer mouse, Peromyscus maniculatus. Canadian Field-Naturalist 113:292-293.

  • Brooks, R. J., and E. M. Banks. 1971. Radio-tracking study of lemming home range. Communications in Behavioral Biology 6:1-5.

  • Castleberry, S., B., T. L. King, P. B. Wood, and W. M. Ford. 2002. Microsatellite DNA analysis of population structure in Allegheny woodrats (Neotoma magister). Journal of Mammalogy 83:1058-1070.

  • Davis, R. and O. G. Ward. 1988. A vacant MICROTUS niche now occupied by the yellow-nosed cotton rat SIGMODON OCHROGNATHUS on an isolated mountain in southeastern Arizona USA. Journal of Mammalogy 69(2): 362-365.

  • Dobson, F. S., and J. O. Murie. 1987. Interpretation of intraspecific life history patterns: evidence from Columbian ground squirrels. The American Naturalist. 129(3): 398-406.

  • Douglass, R. J. 1977. Population dynamics, home ranges, and habitat associations of the yellow-cheeked vole, Microtus xanthognathus, in the Northwest Territories. Canadian Field-Naturalist 91:237-47.

  • Findley, J. S., and W. Caire. 1977. The status of mammals in the northern region of the Chihuahuan Desert. Pages 127-139 in R. H. Wauer and D. H. Riskind, editors. Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico. U.S. National Park Service Transactions and Proceedings Series 3:1-658.

  • Garland, T., Jr. and W. G. Bradley. 1984. Effects of a highway on Mojave Desert rodent populations. American Midland Naturalist 111:47-56.

  • Hall, E. R. 1981a. The Mammals of North America, second edition. Vols. I & II. John Wiley & Sons, New York, New York. 1181 pp.

  • Hoffmeister, D. F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Department. 602 pp.

  • Ingles, L. G. 1965. Mammals of the Pacific States. Stanford University Press, Stanford, California.

  • Jike, L., G. O. Batzli, L. L. Geta. 1988. Home ranges of prairie voles as determined by radiotracking and by powdertracking. Journal of Mammalogy 69:183-186.

  • Krohne, D. T., and G. A. Hoch. 1999. Demography of Peromyscus leucopus populations on habitat patches: the role of dispersal. Canadian Journal of Zoology 77:1247-1253.

  • MacMillen, R. E. 1964. Population ecology, water relations and social behavior of a southern California semidesert rodent fauna. University of California Publications in Zoology 71:1-59.

  • Maier, T. J. 2002. Long-distance movements by female white-footed mice, Peromyscus leucopus, in extensive mixed-wood forest. Canadian Field-Naturalist 116:108-111.

  • Mammalian Species, nos. 1-604. Published by the American Society of Mammalogists.

  • New Mexico Department of Game and Fish. 1997. Fish and Wildlife Information Exchange--VA Tech. Online. Available: Accessed 14 April 1998, last update 29 October 1997.

  • Oxley, D. J., M. B. Fenton and G. R. Carmody. 1974. The effects of roads on populations of small mammals. Journal of Applied Ecology 11: 51-59.

  • Rappole, J. H., and A. R. Tipton. 1987. An assessment of potentially endangered mammals in Texas. Unpublished report to the U.S. Fish and Wildlife Service, Albuquerque, New Mexico. Cooperative Agreement 14-16-0002-86-927. pp. 121-124.

  • Rehmeier, R. L., G. A. Kaufman, and D. W. Kaufman. 2004. Long-distance movements of the deer mouse in tallgrass prairie. Journal of Mammalogy 85:562-568.

  • Smith, M. H. 1965. Dispersal capacity of the dusky-footed wood rat, Neotoma fuscipes. American Midland Naturalist 74:457-463.

  • Storer, T. I., F. C. Evans, and F. G. Palmer. 1944. Some rodent populations in the Sierra Nevada of California. Ecological Monographs 14:166-192.

  • Wilkins, K. T. 1982. Highways as barriers to rodent dispersal. Southwestern Naturalist 27: 459-460.

  • Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at:

  • Wilson, D. E., and S. Ruff. 1999. The Smithsonian book of North American mammals. Smithsonian Institution Press, Washington, D.C. 750 pp.

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