Last modified on 17 October 2012, at 18:11

Field Guide/Mammals/Masked Shrew

sorex cinereus (Masked Shrew)
Family: Soricidae
Size: The masked shrew usually weighs between .08-1.4 ounces (2.5-4.0g) and is approximately 3.9 inches (10cm) in length. Average length of the tail is 1.5 inches (3.9cm), comprising over 40% its the total length.[1]
Description: The fur along the back is brown, while underside fur is white. The coat tends to be darker overall in winter. The tail is brown above and pale underneath, with a blackish tip.[2]

Range: The masked shrew is the most widely distributed shrew found in North America. They occur throughout the northern United States, most of Canada, and Alaska. They do not occur on Vancouver Island, the Queen Charlotte Islands, in tundra habitats, arctic islands, or in extreme northern Quebec.[3]
Habitat: The masked shrew typically live in open and closed forests, meadows, river banks, lake shores, and willow thickets. Habitat suitability depends on the availability of water and the highest population densities can be found in moist environments where water is easily accessible.[4]
Diet: The Masked shrew is omnivorous although they are on the carnivorous side as they primarily eat a variety of insects primarily consisting of ants.They also commonly consume insect larvae and caterpillars.[citation needed]
Activity: Masked shrews are primarily nocturnal and are solitary. They can run fast to protect themselves from predation. [5]

Reproduction: Young become sexually active at 2 months although few females have their first litter until the spring after their birth. Their average litter size is around 6.5 neonates at birth the young can exhibit movements but cannot crawl,see, or hear. they are weaned and grown enough to leave the nest at 27 days of age.[6]
Lifespan: The masked shrew typically lives 1-2 years.[7]

Notes: All shrews (including the masked shrew) have a very high metabolic rate which includes and very fast heart beat. Some shrews have had their heartbeats measured at 1200 beats per minute. To maintain themselves they must eat their weight in food every day. This is accomplished by eating every few minutes. With a heart beating so fast the animals are easily startled and with deadly consequences, as they have been known to die of fright after a loud burst of thunder.
Masked Shrew

  1. Leel, W. (2010), Masked Shrew, http://animaldiversity.ummz.umich.edu/accounts/sorex_cinereus/, retrieved October 10, 2012 
  2. "Sorex Cinereus", Mammalian Species (743): 1-9., 2004, http://www.science.smith.edu/msi/pdf/743_Sorex_cinereus.pdf, retrieved October 10, 2012 
  3. "Sorex Cinereus", Mammalian Species (743): 1-9., 2004, http://www.science.smith.edu/msi/pdf/743_Sorex_cinereus.pdf, retrieved October 10, 2012 
  4. Leel, W. (2010), Masked Shrew, http://animaldiversity.ummz.umich.edu/accounts/sorex_cinereus/, retrieved October 10, 2012 
  5. Leel, W. (2010), Masked Shrew, http://animaldiversity.ummz.umich.edu/accounts/sorex_cinereus/, retrieved October 10, 2012 
  6. Hazardl, E. (1982), "The Masked Shrew", Mammals in Minnesota: 21-27 
  7. Hazardl, E. (1982), "The Masked Shrew", Mammals in Minnesota: 21-27