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least shrew

Cryptotis parva

What do they look like?

Least shrews have thick, short hair that is dark or reddish brown on top in winter. In summer, their fur turns grayish brown. Their tail is dark brown on top, lighter on the bottom, and only 12 to 26 mm long. Their whole bodies are 70 to 92 mm long and weigh 3 to 6 g. Males and females both have scent glands on their flanks, and females have an extra set in front of their ears. (Choate, et al., 1994; Laerm, et al., 2007; Linzey, 1998; Schwartz and Schwartz, 1981; Whitaker, 1974; White and Seymour, 2003)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    3 to 6 g
    0.11 to 0.21 oz
  • Range length
    70 to 92 mm
    2.76 to 3.62 in
  • Average basal metabolic rate
    0.164 W
    AnAge

Where do they live?

Least shrews live mostly in the eastern United States. They are found up the east coast from Florida to New York and as far west as Texas and South Dakota. They also live in Central America, and from northern Mexico to Costa Rica and Panama. (Laerm, et al., 2007; Linzey, 1998)

What kind of habitat do they need?

Least shrews are most commonly found in open fields with tall grasses and places that have fallen trees and brush for protection. They also live near saltwater marshes along the Atlantic Coast. Some are found in the forests of Florida, where they use small plants in the forest for cover. They live at elevations up to 2,100 m. (Choate, et al., 1994; Hafner and Shuster, 1996; Hamilton, 1944; Kale, 1972; Laerm, et al., 2007; Linzey, 1998; Schwartz and Schwartz, 1981)

  • Range elevation
    0 to 2,100 m
    0.00 to ft

How do they reproduce?

Females stop releasing their normal pheromone chemicals right before they are ready to mate. If a female does not want to mate with a particular male, she can get aggressive, making loud noises and arching her back. Females may mate with multiple males in a season. If more than one male is present, the more aggressive ones mate first. (Choate, et al., 1994; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)

Least shrews can reproduce several times during the mating season, which lasts all the way from February to November. Babies grow inside the mother for 21 to 23 days. Females give birth to 2 to 7 young, but 5 on average. Newborns weigh just .34 g, and drink their mother's milk for the first 23 days. Females are able to mate after 40 days, and males after 43 days. (Choate, et al., 1994; Hamilton, 1944; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)

  • How often does reproduction occur?
    Least shrews may breed several times per year.
  • Breeding season
    Breeding of least shrews occurs between February and November.
  • Range number of offspring
    2 to 7
  • Average number of offspring
    5
  • Average number of offspring
    4.5
    AnAge
  • Range gestation period
    21 to 23 days
  • Average gestation period
    21 days
  • Range weaning age
    21 to 23 days
  • Average weaning age
    21 days
  • Range time to independence
    20 to 30 days
  • Average age at sexual or reproductive maturity (female)
    40 days
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    40 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    43 days
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    43 days
    AnAge

Female least shrews care for their young by nursing them for 20 to 23 days. Most adults keep them from getting lost by carrying them around in their mouths. Mothers show panic if separated from their young and, when reunited, gather all of their young together. (Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • male
      • female

How long do they live?

Least shrews tend to live a little over 1 year in the wild. Captive least shrews live can live about 21 months. (Choate, et al., 1994; Laerm, et al., 2007)

  • Range lifespan
    Status: captivity
    21 (high) months
  • Average lifespan
    Status: wild
    1 years
  • Average lifespan
    Status: captivity
    2.6 years
    AnAge

How do they behave?

Least shrews are very social compared to other shrews. They live in large groups called colonies, which can have up to 31 least shrews living together. Their colonies are groups of tunnels that are 24.5 to 150 cm long. They work together to dig the tunnels. Occasionally, they take over tunnels dug out by other small mammals. Least shrews build their nests within the tunnels. Their small round nests are made from plant parts like fallen leaves and grasses. Nests have two or more openings into the tunnel system. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)

Least shrews are active about 11 hours each day, during both the day and night. They are most active at night and least active during very hot and cold months. They spend most of their time staying hidden from predators and hunting. If they hunt down a larger animal, they share food. If food is very scarce, they might eat each other. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)

Home Range

Least shrews mostly look for food in an area of about 0.20 hectares. They defend their nests but not their whole home range. (Choate, et al., 1994)

How do they communicate with each other?

Least shrews make lots of noises. They make make chirps and clicks, some of which humans can't hear. They also use ultrasonic sounds to explore tunnels, which is a kind of echolocation. Males and females also communicate through scent. Males announce their presence to females through their scent. Females only produce a scent when they are not ready to mate or are pregnant. (Schwartz and Schwartz, 1981)

What do they eat?

Least shrews eat a ton of food: 60 to 100% of their own body weight every day. They eat mostly insects, specifically insect larva and centipedes. They can also eat snails, spiders, and crickets. They eat little bits of fungi and other green plants. Least shrews paralyze their prey by attacking their joints. (Choate, et al., 1994; Laerm, et al., 2007; Schwartz and Schwartz, 1981)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • Plant Foods
  • leaves
  • Other Foods
  • fungus

What eats them and how do they avoid being eaten?

Owls are the most common predators of least shrews. Other common predators are rough-legged hawks, foxes, and snakes. House cats and spotted skunks also eat them. If food is scarce, least shrews may also eat each other. Their only defense against predators is camouflage. (Choate, et al., 1994; Linzey, 1998)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

When least shrews burrow, they allow air and nutrients to flow through the soil. Least shrews can eat up to 100% of their body weight in a day and may therefore help control populations of insects. They are also eaten by a variety of predators, such as snakes and owls. Least shrews are known to host various fleas and mites such as Orycteroxenus soricis and Androlaelaps fahrenholzi. (Schwartz and Schwartz, 1981; Whitaker, 1974)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

There are no known negative impacts of least shrews on humans.

How do they interact with us?

Least shrews eat lots of insects, and may help protect crops from harmful insects. They also benefit farmers by loosening up soil when they burrow through it. (Schwartz and Schwartz, 1981)

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

The state of Michigan lists least shrews as threatened, though they have strong numbers in other states. Currently, scientists don't know why populations are declining in Michigan. (Laerm, et al., 2007)

Contributors

Adam Ohl (author), Radford University, Catherine Kent (author), Special Projects, Karen Powers (editor), Radford University, Gail McCormick (editor), Animal Diversity Web Staff.

References

Choate, J., J. Jones, C. Jones. 1994. Handbook Of Mammals of the South-Central States. Baton Rouge and London: Louisiana State University Press.

Dueser, R., J. Porter. 1986. Habitat Use by Insular Small Mammals: Relative Effects of Competition and Habitat Structure. Ecology, 67/1: 195-201.

Formanowicz, D., P. Bradley, E. Brodie. 1989. Food Hoarding by the Least Shrew (Cryptotis parva): Intersexual and Prey Type Effects. American Midland Naturalist, 122/1: 26-33.

Gentry, J., E. Odum. 1957. The Effect of Weather on the Winter Activity of Old-Field Rodents. Journal of Mammalogy, 38/1: 72-77.

Gettinger, R. 1990. Effects of Chemical Insect Repellents on Small Mammal Trapping Yield. American Midland Naturalist, 124/1: 181-184.

Hafner, D., C. Shuster. 1996. Historical Biogeography of Western Peripheral Isolates of the Least Shrew, Cryptotis parva. Journal of Mammalogy, 77/2: 536-545.

Hamilton, W. 1944. The Biology of the Little Short-Tailed Shrew, Cryptotis parva. Journal of Mammalogy, 25/1: 1-7.

Hayssen, V. 1993. Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-Specific Data. Ithaca: Comstock Publishing Associates.

Kale, H. 1972. A High Concentration of Cryptotis parva in a Forest in Florida. Journal of Mammalogy, 53/1: 216-218.

Kivett, V., O. Mock. 1980. Reproductive Behavior in the Least Shrew (Cryptotis parva) with Special Reference to the Aural Glandular Region of the Female. American Midland Naturalist, 103/2: 339-345.

Laerm, J., W. Ford, B. Chapman. 2007. The Land Manager's Guide to Mammals of the South. Durham, NC.: USDA Forest Service and The Nature Conservancy.

Linzey, D. 1998. The Mammals of Virginia. Blacksburg, Virginia: The McDonald & Woodward Publishing Company.

Pfeiffer, C., G. Gass. 1963. Note on the Longevity and Habits of Captive Cryptotis parva. Journal of Mammalogy, 44/3: 427-428.

Schwartz, C., E. Schwartz. 1981. The Wild Mammals of Missouri. Columbia & London: University of Missouri Press and Missouri Department of Conservation.

Whitaker, J. 1974. Cryptotis parva. Mammalian Species, 43: 1-8.

Whitaker, J., N. Wilson. 1968. Mites of Small Mammals of Vigo County, Indiana. American Midland Naturalist, 80/2: 537-542.

White, , Seymour. 2003. Mammalian Basal Metabolic Rate is Proportional to Body Mass2/3. Proc Natl Acad Sci, 100: 4046-4049.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Ohl, A. and C. Kent 2012. "Cryptotis parva" (On-line), Animal Diversity Web. Accessed August 22, 2014 at http://www.biokids.umich.edu/accounts/Cryptotis_parva/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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