Cryptotis parva (Say, 1823), Nebraska, United States. The mosaic occurrence of relic Pleistocene populations has recently been indicated in an allozyme study from the southwestern United States.
OTHER COMMON NAMES
French: Petite musaraigne a queue courte; German: Nordamerikanische Kleinohrspitzmaus.
Head and body length 2.2-3.1 in (5.5-7.8 cm); tail 0.4-1.1 in (1-2.7cm); weight 0.1-0.3 oz (4-8 g). Soft brown-black fur with white underside.
Southeastern Canada through the east-central and southwestern United States and Mexico to Panama and Costa Rica. The only species of the genus found north of Mexico.
A habitat specialist among shrews, living in open grassy habitats and along streams in otherwise dry habitats. Also found in cold, wet forest. Occurs from the lowlands to 7,900 ft (2,400 m). In Central America usually above 2,600 ft (800 m).
Somewhat gregarious and colonial. May form quite large colonies of up to 30 adult individuals. Group members share one nest, rest in huddling, cooperate in burrow building, and share a common home range. They emit a variety of sounds that seem to correspond to friendly social behavior. All these facts suggest that lack of territoriality and group living is characteristic of the social system of this species. It is active throughout the year and at all hours of the day, with greatest activity during the night. This species uses runways and burrows of other small mammals, but also makes its own tunnels in loose, soft soils. Ultrasonic clicks are also given, which may be used for echolocation.
FEEDING ECOLOGY AND DIET
Feeds on invertebrates (insect larvae, centipedes, and earthworms), small lizards and frogs, and carrion.
This promiscuous species probably breeds throughout the year in the southern parts of its geographic range, and the greatest reproduction activity was recorded in winter and spring. The gestation period is 21-22 days, and the mean litter size is 4-5 young (range 1-9). Population density of about 12-13 individuals per acre (31 per ha) was recorded. Average life expectancy in the laboratory was eight months, with a maximum longevity of 31 months.
SIGNIFICANCE TO HUMANS
Laboratory breeding colonies of least shrews have been established. The species has become an important biomedical research model. ♦
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