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Cryptotis parvaleast shrew

By Adam Ohl and Catherine Kent

Geographic Range

Least shrews, Cryptotis parva, occur in greatest densities in the eastern United States. Their geographical range extends from Florida to New York and reaches as far west as Texas and South Dakota. Least shrews also occur in Central America from northern Mexico to Costa Rica and into Panama. (Laerm, et al., 2007; Linzey, 1998)

Habitat

Least shrews are most commonly found in open fields with tall grasses or areas with fallen trees and brush that provide protection. Least shrews can also be found in softer soil near saltwater marshes along the Atlantic Coast. Some occur in the forests of Florida, relying on the underbrush for cover. Least shrews have been found at elevations as high as 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

Physical Description

Least shrews have dense, short hair, which is dark brown to reddish brown on the dorsal side during the winter. During the summer, fur becomes grayish brown in color. They have a bicolored tail, with a darker brown on top and a lighter underside. Least shrews measure 70 to 92 mm in length and usually weigh between 3 and 6 g. Members of this species have two distinct ear holes hidden in their fur. Males and females both have scent glands on their flanks, and females have an extra set in front of their ears. Females have six mammae along the lower body. Least shrews can be distinguished from other closely related species by both their tail length and dentition. The tail of least shrews is relatively short and measures 12 to 26 mm. Unlike related species which have three, least shrews have four unicuspid teeth, though the fourth is very small and hidden. (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

Reproduction

Mating of least shrews generally occurs within the nest. Females alert all males sharing the nest and males in adjoining areas that they are ready to mate by stopping the release of pheromones from their scent glands. When this scent is absent, males show interest by sniffing both the anal glands and glands located in front of the ears of a female. The male then attempts to mount the female. If she is unreceptive, the female may become aggressive, making loud noises and arching her back. The male then ceases its approach and lays on its back, exposing both its neck and belly until he is ready to make another attempt. Females show signs of receptiveness by lifting their tail and presenting themselves. When more than one male is present, aggression levels determine a male hierarchy, and the most aggressive males mate first. Once mating is complete, males take a dominant station over the female. The mating process on average lasts 3 days. (Choate, et al., 1994; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)

Least shrews may reproduce several times during the mating season, which lasts from February to November. Gestation lasts 21 to 23 days. Females give birth to an average of 5 young per litter, though litters can range from 2 to 7 individuals. Newborn least shrews weigh approximately 0.34 g. Young are weaned at about 23 days of age. Males reach sexual maturity around 43 days of age and females around 40 days. (Choate, et al., 1994; Hayssen, 1993; Kivett and Mock, 1980; Schwartz and Schwartz, 1981; Whitaker, 1974)

  • Breeding interval
    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 provide almost a full month of care to their young, which are nursed for 20 to 23 days. Most adult members within the nest take an active role in preventing juveniles from getting lost by carrying them in their mouths. Mothers show panic when separated from their young and, when reunited, gather all 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

Lifespan/Longevity

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

Behavior

Least shrews are very social compared to other shrews. Though uncommon, large colonial settlements of up to 31 shrews in one nest have been found. Although they occasionally take over tunnels created by other small mammals, least shrews are capable of digging their own tunnels, which can range in length from 25.4 to 150 cm. Least shrews have been observed cooperatively digging their tunnels. Nests are generally built within the tunnel system, constructed from a variety of plant matter such as fallen leaves and grasses. Nests are small and round and no more than 20 cm in diameter. They have two or more openings that lead into the tunnel system. Nests have also been found underneath fallen trees and rocks, separate from the tunnel system. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)

Least shrews are estimated to be active for 11 hours each day, throughout both the day and night. Activity peaks at night and decreases during extremely hot and cold months. The majority of a least shrew's time is spent staying hidden or hunting. Least shrews share food when feeding on a larger organism. When food is scarce, least shrews have been known to resort to cannibalism. (Choate, et al., 1994; Linzey, 1998; Schwartz and Schwartz, 1981)

Home Range

Least shrews have a home range of about 0.20 ha. They strictly defends their nest but not their entire home range. (Choate, et al., 1994)

Communication and Perception

Least shrews are very vocal. They make a variety of high frequency sounds including chirps and clicks, some of which are inaudible to humans. Least shrews also use ultrasonic sounds for tunnel exploration. This form of echolocation may be useful while moving underground, but there is no proof that this species uses sound to hunt. Males and females also communicate through scent. Males announce their presence to females through their scent. Females, however use their scent differently; when females stop producing pheromones, they are ready to mate. When females produce a scent, they are not ready to mate or are pregnant. (Schwartz and Schwartz, 1981)

Food Habits

Least shrews have immense dietary needs. They generally eat 60 to 100% of their own body weight every day. Least shrews are largely insectivorous, and their diet primarily consists of insect larva and centipedes. They also have been known to eat snails, spiders, and crickets. Least shrews immobilize their prey by attacking the joints of the organism so they cannot flee. The species has also been known to eat small quantities of fungi and other green plants. (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

Predation

Owls are the most common predators of least shrews. Other common predators include rough-legged hawks, foxes, and snakes. Domesticated house cats and spotted skunks are also known predators. When food is scarce, least shrews may also resort to cannibalism. Their ability to stay camouflaged is the only defense of least shrews against predators. (Choate, et al., 1994; Linzey, 1998)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Because of their burrowing habits, least shrews aerate soil and aid the transport of nutrients within soil. Least shrews can eat up to 100% of their body weight in a day and may contribute to regulation of insect populations. 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/Parasitic Species

Economic Importance for Humans: Positive

Least shrews are highly insectivorous and may inadvertently help protect crops from harmful insects. Shrews also aerate soil, which is a benefit to agricultural practices. (Schwartz and Schwartz, 1981)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

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

Conservation Status

A national survey in 2007 listed Cryptotis parva as a secure species in the United states. However, the state of Michigan lists least shrews as threatened. Currently, no conservation efforts are in place; little is known as to 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.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cooperative breeder

helpers provide assistance in raising young that are not their own

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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.

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