Plants and Animals
Cryptotis parva Least shrew
Key Characteristics
The least shrew is one of the smallest of Michigan's shrews, with a body length of 2.5 to 3.3 inches (6.4 - 8.3 cm) and a short tail 0.5 to 0.75 inches (1.3 - 1.9 cm) long. Like many shrews, it has an elongated head, pointed nose, tiny eyes, and short grayish brown fur.
Status and Rank
US Status: No Status/Not Listed
State Status: T - Threatened (legally protected)
Global Rank: G5 - Secure
State Rank: S1S2 - Rank is uncertain, ranging from critically imperiled to imperiled
Occurrences
| County | Number of Occurrences | Year Last Observed |
|---|---|---|
| Calhoun | 1 | 1929 |
| Clinton | 2 | 1960 |
| Ingham | 1 | 1945 |
| Jackson | 1 | 1922 |
| Kalamazoo | 2 | 1943 |
| Livingston | 2 | 1939 |
| Oakland | 1 | 1937 |
| Washtenaw | 7 | 1958 |
| Wayne | 1 | 1932 |
Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.
Habitat
The least shrew inhabits dry upland meadows with dense coverage of grasses and forbs. It can also be found in marshy areas, fencerows, and woodland edges. Nests are often found tucked under rocks, logs, discarded lumber, metal sheeting, and hay bales left in fields over winter.
Natural Community Types
- Bur oak plains
- Dry sand prairie
- Dry-mesic prairie
- Lakeplain oak openings
- Mesic prairie
- Mesic sand prairie
- Oak barrens
- Oak openings
For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.
Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.
Management Recommendations
The management needs for this species are poorly understood, other than the need to maintain grassy upland habitat with a dense cover of vegetation. Populations have severely declined due to natural phenomena, genetic limitations, and/or intensive land use by humans.
Active Period
Breeding from first week of March to fourth week of November
Survey Methods
Least shrews are active year-round, day and night, but activity is thought to peak during night, early pre-dawn before sunrise, and later afternoon. A large majority of specimens found in Michigan were captured between October and March, despite year-round effort. Least shrews typically do not build burrows and prefer to remain under objects during the day.
Drift fence trapping with pitfall traps
Survey Period: From first week of October to fourth week of March
Survey Method Comment: Best to survey at night, early pre-dawn before sunrise, and late afternoon to evening.
Live trap
Survey Period: From first week of October to fourth week of March
Survey Method Comment: Best to survey at night, early pre-dawn before sunrise, and late afternoon to evening.
References
Survey References
- Kurta, A. 1995. Mammals of the Great Lakes Region. The University of Michigan Press, Ann Arbor.
- Wilson, D.E., F.R. Cole, J.D. 1996. Measuring and Monitoring Biological Diversity - Standard Methods for Mammals. Smithsonian Institution Press, Washington D.C.
Technical References
- Baker, R.H. 1983. Michigan Mammals. Michigan State University Press, East Lansing.
- Evers, D.C. 1994. Endangered and Threatened Wildlife of Michigan. The University of Michigan Press, Ann Arbor. 412pp.
- Kurta, A. 1995. Mammals of the Great Lakes Region. The University of Michigan Press, Ann Arbor.