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Sorex cinereuscinereus shrew(Also: masked shrew)

By Wendy Lee

Ge­o­graphic Range

Sorex cinereus, com­monly called the Masked shrew or com­mon shrew, is the most widely dis­trib­uted shrew found in North Amer­i­can. Com­mon shrews 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. (Nagorsen, 1996; van Zyll de Jong, 1983).

Habi­tat

Com­mon shrews oc­cupy a di­ver­sity of habi­tats, most com­mon are 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. Com­mon shrews also do well in dis­turbed habi­tats such as those dis­turbed by fire or log­ging. The av­er­age home range is 0.6 hectares (Nagorsen, 1996; Pagels, et al. 1994)).

Phys­i­cal De­scrip­tion

Sorex cinereus is the sec­ond small­est shrew species. Sorex hoyi is slightly smaller. Al­though sim­i­lar in size, their col­oration is quite dif­fer­ent. There is no sig­nif­i­cant sex­ual di­mor­phism in com­mon shrews. Dor­sal fur is brown, ven­tral fur is grey­ish-white. Pelage tends to be darker over­all in win­ter. The tail is brown above and pale un­der­neath, with a black­ish tip. Av­er­age length of the tail is 39.9mm, com­pris­ing over 40% of the total length. Av­er­age length of adults is 99 mm. Young are born hair­less and with fused eye­lids, they weigh from 0.2 to 0.3 grams and are 15 to 17 mm long in­clud­ing a 3 mm long tail (Nagorsen, 1996; Wil­son and Ruff, 1999; van Zyll de Jong, 1983).

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    2.5 to 4.0 g
    0.09 to 0.14 oz
  • Average length
    99.0 mm
    3.90 in
  • Average basal metabolic rate
    0.238 W
    AnAge

Lifes­pan/Longevity

Masked shrews prob­a­bly do not live much past 1 to 2 years old, most prob­a­bly die be­fore reach­ing adult­hood.

  • Typical lifespan
    Status: wild
    2.0 (high) years

Be­hav­ior

Com­mon shrews are most ac­tive after dark, when 85 per cent of ac­tiv­ity oc­curs. They are es­pe­cially ac­tive be­tween 01:00 and 02:00, when there has been a rain­fall, or on very dark nights. Their pri­mary ac­tiv­ity is hunt­ing. Com­mon shrews hunt pri­mar­ily on the ground but may also climb into low veg­e­ta­tion and shrubs. They run quickly, can jump to 10-15 cm high, and dig in loose sub­strate (Nagorsen, 1996; van Zyll de Jong, 1983).

Com­mu­ni­ca­tion and Per­cep­tion

Lit­tle is known of com­mu­ni­ca­tion in masked shrews. They have an ex­cel­lent sense of smell and can see fairly well. They use their sen­si­tive whiskers to find their way around and de­tect prey. Masked shrews also prob­a­bly squeak and hiss as a way of com­mu­ni­cat­ing.

Food Habits

Be­cause Sorex cinereus in­hab­its a wide range there is great ge­o­graphic vari­a­tion in diet. Ants rep­re­sent 50% of the food source for com­mon shrews in Michi­gan, whereas in­sect lar­vae are the dom­i­nant prey item in New Brunswick. Kelp flies and ma­rine am­phipods are major di­etary items in Nova Sco­tia. They are also im­por­tant preda­tors of for­est in­sect pests such as Jack Pine Bud­worms and Larch Sawflies. In gen­eral, com­mon shrews con­sume a va­ri­ety of in­ver­te­brates in­clud­ing in­sect lar­vae, ants, bee­tles, crick­ets, grasshop­pers, spi­ders, har­vest­men, cen­tipedes, slugs, snails. Seeds and fungi are also con­sumed (Nagorsen, 1996).

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

Pre­da­tion

Masked shrews avoid being preyed upon by stay­ing under cover and being ac­tive mostly at night, they are rarely seen.

Ecosys­tem Roles

Masked shrews can be very abun­dant in the com­mu­ni­ties in which they live. They can have a dra­matic im­pact on in­sect com­mu­ni­ties be­cause they have to con­sume such large quan­ti­ties of in­sects. They are also im­por­tant prey items for many small preda­tors.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

The ex­tent to which com­mon shrew pop­u­la­tions af­fect hu­mans is un­known. How­ever, they have a sig­nif­i­cant im­pact on pop­u­la­tions of in­sect pests and are im­por­tant mem­bers of com­mu­ni­ties (Nagorsen, 1996).

  • Positive Impacts
  • controls pest population

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Neg­a­tive im­pacts of S. cinereus are un­known. How­ever, they may af­fect pop­u­la­tions of some ben­e­fi­cial or­gan­isms or in­hibit re­pro­duc­tion of some plants by con­sum­ing seeds (Nagorsen, 1996).

Con­ser­va­tion Sta­tus

Com­mon shrews are com­mon and wide­spread and none of the Genus Sorex, in­clud­ing Sorex cinereus, are con­sid­ered to be threat­ened or en­dan­gered species (Boyd et al., 1999; Nagorsen, 1996; Wil­son and Ruff, 1999).

Con­trib­u­tors

Wendy Lee (au­thor), Uni­ver­sity of Toronto.

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

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

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.

internal fertilization

fertilization takes place within the female's body

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).

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

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

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

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

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).

viviparous

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

Ref­er­ences

Boyd, S., K. Car­lin-Mor­gan, B. Coslick, A. Ed­wards, M. Flood. June 1, 2000. "Mam­mals: Sorex cinereus, S. fumeus, S. lon­girostris & Mi­crosorex hoyi" (On-line). Ac­cessed Oc­to­ber 6, 2000 at http://​museum.​nhm.​uga.​edu/​~GA Wildlife/.

Nagorsen, D. 1996. Opos­sums, Shrews and Moles of British Co­lum­bia. UBC Press/Van­cou­ver: Royal British Co­lum­bia Mu­seum Hand­book ISSN 118-5114.

Pagels, J., K. Uthus, H. Duval. 1994. The Masked Shrew, Sorex cinereus, in a Re­lict­ual Habi­tat of the South­ern Ap­plachian Moun­tains. Pp. 103-109 in J Mer­ritt, G Kirk­land, R Rose, eds. Ad­vances in the Bi­ol­ogy of Shrews. Pitts­burgh, PA: Carnegie Mu­seum of Nat­ural His­tory Spe­cial Pub­li­ca­tion No. 18.

Wil­son, D., S. Ruff. 1999. The Smith­son­ian Book of North Amer­i­can Mam­mals. Wash­ing­ton and Lon­don: Smith­son­ian In­sti­tu­tion Press.

van Zyll de Jong, C. 1983. Hand­book of Cana­dian Mam­mals. vol. 1, Mar­su­pi­als and In­sec­ti­vores. Ot­tawa, Canada: Na­tional Mu­se­ums of Canada.

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