Mammal Species of the World
- Original description: Diersing, V. A., and D. F. Hoffmeister, 1977. Revision of the shrew Sorex merriami and a description of a new species of the subgenus Sorex, p. 329. Journal of Mammalogy, 58:321-333.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (5000-200,000 square km (about 2000-80,000 square miles)) The range includes portions of the southwestern United States and northern Mexico; the species is presently known only from the Huachuca, Santa Rita, and Chiricahua mountains of southeastern Arizona, the Animas mountains of southwestern New Mexico, and the Sierra Madre Occidental of Chihuahua, Mexico (Caire et al. 1978, Junge and Hoffman 1981, Simons and Hoffmeister 2003). Elevational records range from 1,575 to 2,590 meters (Simons and Hoffmeister 2003).
Length: 11 cm
Size in North America
Average: 101 mm
Range: 79-114 mm
Average: 3.3 g
Range: 1.9-5.2 g
See Carraway (1995) for a key to western North American soricids based primarily on dentaries.
Comments: This shrew nearly always is found beneath a thick canopy of vegetation (Simons, in Wilson and Ruff 1999). It has been collected in montane conifer forest and encinal and Mexican oak-pine woodland, in relatively mature forest with substantial understory vegetation and debris (e.g., logs, stumps), often in canyons along riparian edges of pine-oak forest, such as among horsetails near a spring in dense woodland (oak, walnut maple, sycamore, and some Douglas-fir), in thick woodland where large boulders were present with large pines, walnuts, oaks, and maples, and along a dry wooded streambed (Hoffmeister 1986, Simons and Van Pelt 1999, Simons and Hoffmeister 2003).
Habitat and Ecology
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: Feeds primarily on insects and other small invertebrates. Forages actively under cover of forest litter.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 6 - 80
Comments: This shrew is represented by a relatively small number of known occurrences or subpopulations. It is known from three mountain ranges in Arizona, one mountain range in New Mexico (see New Mexico Department of Fish and Game 1996), and one specimen from Mexico (Simons and Hoffmeister 2003). There are at least 15 documented occurrences in Arizona (11 occurrences are extant; S. Schwartz, pers. comm., 1997). Surveys conducted in 2001 documented the presence of this shrew at two locations within the Animas Mountains in New Mexico (Simons, unpub. data).
This shrew is difficult to distinguish from S. monticolus (Arizona Game and Fish Department 1997), and it is difficult to capture in pitfall traps even in at known localities (see Simons et al. 1990). It seems possible that this species will be found in additional mountain ranges near the known range (Frey 2004).
2500 - 1,000,000 individuals
Comments: Total adult population size is unknown but presumably is at least a few thousand. Simons and Van Pelt (1999) reported that S. arizonae occurred widely in two mountain ranges in Arizona and was reasonably abundant at several sites.
This shrew has been reported as rare and extremely localized in New Mexico (see New Mexico Department of Game and Fish 1996).
Little information available. May occur with S. MERRIAMI and S. MONTICOLUS.
Life History and Behavior
Comments: Active throughout the year. Periods of activity followed by periods of rest throughout the day and night.
Nothing known about this species, but the closely related Merriam's shrew is known to produce litters of 5-7 young, born in the summer.
National NatureServe Conservation Status
Rounded National Status Rank: N2 - Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: The status of this shrew is poorly documented, but it occurs in several locations in at least five mountain ranges in Arizona, New Mexico, and northern Mexico, and it is probably more widely distributed than currently known. Trend is not known, and threats are unclear (but probably not too severe). Potential threats include removal of downed woody debris through understory clearing and firewood collection; intense ground-burning fires that remove ground structure could cause local extirpations; possibly threatened by livestock grazing and development of recreation sites in Arizona.
IUCN Red List Assessment
Red List Category
Red List Criteria
Global Long Term Trend: Increase of 10-25% to decline of 30%
Comments: Long-term trend is unknown, but there appears to be little reason to suspect that a major change has occurred in the extent of occurrence, area of occupancy, number of subpopulations, or population size.
Degree of Threat: Medium
Comments: If this species is as rare and restricted in distribution as it appears to be in some areas (e.g., Animas Mountains, New Mexico), it may be vulnerable to localized adverse habitat alterations (see New Mexico Department of Game and Fish 1996). Potential threats include habitat alteration and degradation caused by removal of downed woody debris through understory clearing and firewood collection; intense ground-burning fires that remove ground structure could cause local extirpations (Arizona Game and Fish Department 1996). Locally, this shrew might be threatened by livestock grazing and development of recreation sites in Arizona (see New Mexico Department of Game and Fish 1996). However, the responses of this species to various habitat alterations and management practices are poorly known, and the scope of threat could not be determined in this assessment.
Biological Research Needs: More information is needed on life history and habitat requirements.
Global Protection: Few to several (1-12) occurrences appropriately protected and managed
Comments: Some occurrences are in Fort Huachuca Military Reservation and Coronado National Forest, but this does not necessarily ensure protection.
The Arizona shrew is one of the smaller species of shrew, with a head and body 5 to 7 cm (2.0 to 2.8 in) in length, and a tail about 4 cm (1.6 in) long. When filly grown, they weigh an average of only 3.5 g (0.12 oz). Their fur ranges from grey to brown, and is paler on the underparts of the animal. Long thought to be the same as Merriam's shrew, it was identified as a separate species in 1977, and can be physically distinguished only by fine details of the skull and teeth.
Distribution and habitat
The Arizona shrew is found in Chihuahua in Mexico, and in southern Arizona and New Mexico in the United States. It inhabits forested mountainous terrain between 1,575 and 2,590 m (5,167 and 8,497 ft) dominated by coniferous trees or by mixed pine and oak. There are no known subspecies.
Arizona shrews inhabit primary forest with heavy undergrowth, and are particularly common in mesic riverine canyons. Despite their preference for such canyons, they are not necessarily found close to open water. They apparently breed between late July and October. They are believed to have diverged from the closely related Merriam's shrew relatively recently, during the late Pleistocene or early Holocene.
- Woodman, N., Matson, J. & Castro-Arellano, I. (2008). "Sorex arizonae". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved 8 February 2010.
- Simons, L.H. & Hoffmeister, D.H. (2003). "Sorex arizonae". Mammalian Species: Number 732: pp. 1–3. doi:10.1644/732.
- Diersing V.E. & Hoffmeister, D.H. (1977). "Revision of the shrew Sorex merriami and a description of a new species of the subgenus Sorex". Journal of Mammalogy 58 (3): 321–333. doi:10.2307/1379331.
- George, S.B. (1988). "Systematics, historical biogeography, and evolution of the genus Sorex". Journal of Mammalogy 69 (3): 443–461. doi:10.2307/1381337.
Names and Taxonomy
Comments: See George (1988) for electrophoretic study of systematic relationships among Sorex species. First described in 1977 (Diersing and Hoffmeister 1977); electrophoretic data support separation of this species from S. merriami (George 1988).