Northern Short-tailed Shrew
Common Names: giant mole shrew
Species: Blarina brevicauda
Blarina brevicauda, also known as the giant mole shrew, is a very unique and interesting specimen of the Soricidae Family. Unlike most shrews, Blarina is a robust-looking shrew which has a short and heavy snout, a short tail, small poorly developed eyes, and ears which are almost completely hidden by fur. The head and body length is 75-136 mm , hind foot is 13-18 mm, and the tail length is 17-30 mm. It is the largest of the native shrews of eastern Canada weighing in at 12-27 grams. The skull is the largest and most of the shrews of eastern Canada and has well-developed crests and ridges. The skull tends to become more angular, the tip of the rostrum becomes thicker and the first incisors are forced downwards with advancing age. The male skull is slightly larger than that of the female. Blarina has velvety and soft fur which is usually uniformly dark gray with underparts being only slightly paler, but in the summer its pelage is a shade paler. There do exist partially albino Blarina brevicauda which have bold whits stripes.
The northern short-tailed shrew has several identifying features which distinguish it from other shrews. Blarina have well-developed skin glands on the flanks, especially in the males, that emit a strong, pungent odour that makes them unpalatable to many predators such as hawks, owls, and fishers. A unique characteristic of this mammal is the sub-maxillary glands that emit a poison at the base of the lower incisor teeth. This poison, which only causes pain and red swelling that lasts for several days in humans who are bitten, quickly immobilizes small animals when they are bitten. Animals up to the size of small rabbits are known to have been attacked and killed by Blarina.
The nearctic distribution of northern short-tailed shrews includes most of North America from Southern Saskatchewan and Nova Scotia to central Nebraska and Georgia. In eastern Canada, this mammal inhabits the southern half of Ontario as well as the southernmost regions of Quebec. Blarina inhabits the entirety of New Brunswick, Nova Scotia and Prince Edward Island, Canada.
Short-tailed shrews are found in nearly all terrestrial habitats. However, their populations are most dense in damp, brushy woodlands, bushy bog marshes, and weedy borders of fields. This shrew is also common in cultivated fields, flower and vegetable gardens, fence rows, and beside country roads. Blarina brevicauda prefers to live in temperate forests with deep litter that is not very dry.
Short tailed shrews are covetous eaters and must feed frequently, mostly in the early and late afternoon. It is estimated that they consume and metabolize as much as three times their weight in food per day. Blarina brevicauda eats mainly invertebrates, small vertebrates, and plant material. The toxic material produced by its sub-maxillary salivary glands proves effective in subduing prey much larger than itself including salamanders, frogs, snakes, mice, birds, and other shrews. This mammal again shows its unique flavour by being one of the few shrews to store its food for winter, including snails and beetles. In captivity, Blarina puts nutmeats, sunflower seeds and other edibles into storage.
Northern short-tailed shrews construct elaborate mating nests, 150-250 mm long by 150 mm wide, which are built out of shredded grass or leaves and placed in tunnels or under logs and rocks. Their breeding season begins in early spring and ends in early autumn (March-September). Females can possibly have up to as many as three litters per year, but usually have two litters of 3-10 individuals. The gestation time for Blarina brevicauda is 21-22 days, with the young leaving the nest when 18-20 days old. Females reach sexual maturity at six weeks, while males mature at twelve weeks. The life span of these resplendent creatures can last up to three years, but is usually closer to 18 weeks.
Northern short-tailed shrews are active all year round, both day and night, although they are more nocturnal than diurnal. They are known for creating tunnels through leaves, plant debris and snow with their strong paws and cartilaginous snouts. They make their own runways tunnels and nests but also use the tunnels of mice and moles, which is why they are also known as the ‘giant mole shrew’. Most of Blarina’s time is spent underground in tunnels, however they have been known to climb nearly two metres up a tree trunk to get to bird feeders.
Blarina is not a sociable animal, being solitary and territorial. This mammal marks its territory with scent and will physically threaten intruders. The northern short-tailed shrew often serves as an important check on insect crop pests, especially the larch sawfly. It also destroys snails and mice that damage crops proving to be advantageous to humans.
There is no special status for Blarina brevicauda. This shrew is believed to the most numerous mammal in the United States, and is especially common in the areas surrounding the Great Lakes. Its population undergoes frequent fluctuations which are yet to be understood.