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.
Perception Channels: tactile ; chemical
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).
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
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).
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
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.
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)
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).
Biogeographic Regions: nearctic (Native )
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)).
Habitat Regions: temperate
Terrestrial Biomes: forest ; rainforest
Wetlands: marsh ; swamp
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.
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).
Range mass: 2.5 to 4.0 g.
Average length: 99.0 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.238 W.
Masked shrews avoid being preyed upon by staying under cover and being active mostly at night, they are rarely seen.
Known Predators:
The breeding season for Sorex cinereus occurs from April to October in eastern North America but may extend into November if food is plentiful. Length of gestation is unknown. The average number of embryo produced by various populations ranges from five to eight across North America, with at least two litters produced by a female in a breeding season. Both males and females may breed in their first summer but this is not typical (Nagorsen, 1996).
Breeding season: Masked shrews breed from April to November.
Range number of offspring: 4.0 to 10.0.
Average weaning age: 20.0 days.
Range age at sexual or reproductive maturity (female): 5.0 to 11.0 months.
Range age at sexual or reproductive maturity (male): 5.0 to 11.0 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Average birth mass: 0.28 g.
Average gestation period: 19 days.
Average number of offspring: 6.22.
Young are cared for and nursed by their mother in her nest until they reach about 20 days old.
Parental Investment: altricial ; female parental care
The cinereus shrew or masked shrew (Sorex cinereus) is a small shrew found in Alaska, Canada, and the northern United States.[2] This is the most widely distributed shrew in North America, where it is also known as the common shrew.
It is grey-brown in colour with a light grey underside and a pointed snout. It has a long tail that is brown on top and pale underneath with a dark tip. Its body is about 9 cm (3.5 in) in length including a 4 cm (1.6 in) long tail. It weighs about 5 g (0.18 oz). It has darker colouring than other shrews. Masked shrews can live up to two years, but, on average, only survive eighteen months.
In a long-term study done in Alaska, Yom-Tov and colleagues (2005) found that the masked shrew's body size contradicts Bergmann's Rule.[3] The study, done on 650 specimens and spanning from 1950 to 2003, examined body size in relation to ambient temperature. Measurements of body weight and the length of the tail, ear, hind foot, and body were taken. Results yielded that the masked shrew's body size decreased with high latitudes and with lower mean January temperatures, a trend that opposed Bergmann's Rule. It was suggested that this may be a coping mechanism to limit total energy requirements due to decreased food availability in winter months. Additionally, it was shown that body and tail length increased with rising temperatures during the second half of the twentieth century. This may be due to higher temperatures increasing the availability of the shrew's main diet.
The masked shrew is the most widely distributed shrew.[4] Its range covers most of northern North America extending south as far down to Maryland, along the Rocky Mountains in the west, and to the Appalachians in the east. This species was introduced into Newfoundland in the late 1950s. It can be found in many types of habitat like arid grasslands, moist areas, woodland, and tundra. The masked shrew mostly lives in humid areas and with high levels of vegetation to hide in. Moisture determines the abundance of this shrew.
Predators include larger shrews, hawks, owls, shrikes, snakes, herons, foxes, leopard frogs, bluebirds, brown trouts, and weasels. Masked shrews are susceptible to many types of parasites, like fleas and tapeworms.[5] Cowan and colleagues (2007) found that the high volume of food masked shrews consume causes them to be more susceptible to parasitism. Since males have larger ranges, they have a higher exposure to parasites.[5]
Masked shrews are opportunistic generalists. They eat insects, worms, snails, small rodents, salamanders, and seeds. Due to its high metabolism, the masked shrew can eat three times its weight a day.[6] The shrew has to eat almost constantly, because they can only survive a few hours without food.[6] Their metabolism drops when they are at rest.
McCay and colleagues (1997) found a higher abundance of masked shrews in non-irrigated forests due to a higher availability of larval insects, which is the preferred food source of the masked shrew. Masked shrews chose Lepidoptera larva over other food sources.[7]
This animal is active day and night year-round. Masked shrews can be nocturnal or diurnal depending on the weather. Doucet and colleagues (1974) showed that rain increases the nocturnal activity of the masked shrew, while cloud cover increases day and night activity.[8] It digs tunnels but also uses tunnels created by other small mammals. It uses dry grass to make nests in these tunnels. It can make high frequency pulses and has lateral scent glands. The home range of the masked shrew depends on availability of food, but it is on average 0.55 hectare. It has a low tolerance for other shrews in its home range. Merritt and colleagues (1995) found that its mass declined by half from summer to winter and non-shivering heat production, energy conservation, and reduced body mass.[4]
Masked shrews living at high latitudes are born in late spring and summer, reach adult size by the time they leave their nests, and complete their life cycle within a year.[3] They are born during spring or summer, remain immature in winter, and breed the following spring.[4] Masked shrews breed from May to September. Females have one litter of 6 to 7 young during the breeding season. The young are born hairless and clawless and have translucent abdominal walls.[6] Body mass increases and peaks at twenty days, then decreases when the young leave the nest after about 27 days. Masked shrews have a high chance of mortality during their first two months of life and most die during the first year. Masked shrews become sexually mature at two months, but wait until their first spring to breed.
The cinereus shrew or masked shrew (Sorex cinereus) is a small shrew found in Alaska, Canada, and the northern United States. This is the most widely distributed shrew in North America, where it is also known as the common shrew.
