The Northern short-tailed shrew is the largest shrew in its genus and occurs in the northeastern region of North America. It is a highly active, and voracious insectivore. It is notable in that it is one of the few venomous mammals. The dorsal fur is thick and velvety and can be black, brownish black, or silvery gray, with the ventral fur being a bit lighter and grayer. These shrews molt from a summer coat which is shorter and paler than the winter pelage in October and November, and back again sometime in February through July.
Northern short-tailed shrews are found throughout central and eastern North America, from southern Saskatchewan to Atlantic Canada and south to northern Arkansas and Georgia. They are probably the most common shrews in the Great Lakes region. These small animals inhabit both disturbed and undisturbed habitats, including grasslands, old fields, fencerows, marshy areas, deciduous and coniferous forests, and household gardens. Preferred habitats are those which are moist with leaf litter or thick plant cover.
Northern short-tailed shrews are active year-round and tend to be more nocturnal than diurnal. They usually forage within a few hours after sunset, though they are also active during cloudy days. While other shrews spend more time above ground, Northern short-tailed shrews prefer to tunnel along below ground, through the leaf litter, or at the snow/ground interface. They can dig at a rate of 2.5 cm/min, in between resting. These shrews construct a nest up to 20 cm (8 in) in diameter underground or underneath a log and often line it with leaves or the fur of the meadow vole. They keep their nests clean and deposit wastes outside the nest in a latrine area. Other parts of the burrow system are used for food storage. Northern short-tailed shrews are typically solitary and exhibit several aggressive displays and vocalizations to ward off other members of the species when encounters occur. Their sense of smell is thought to be poor, and vision is thought to be limited to the detection of light, but they compensate by using echolocation and a fine sense of touch.
Northern short-tailed shrews are carnivores. They prefer insects, earthworms, voles, snails, and other shrews for the bulk of their diet, though salamanders and mice are also eaten. Being carnivorous animals, these shrews may also eat small quantities of subterranean fungi and seeds.
Little is known about the mating system in Northern short-tailed shrews. Mating usually occurs from March through September, though most births occur early or late in that period. Males in captivity were observed to make clicking sounds while courting a female. Females have two litters per season, though three are possible. Gestation lasts 21-24 days, and six to eight young are usually born. Shrewlets are suckled for up to 25 days before they are weaned. The female strengthens the nest when the young are nursing, and is more active to support her increased nutritional needs. The young, which were born hairless and blind and weighing less than a gram, may become reproductively mature as soon as 2-3 months; those born in the spring mature more quickly than those born late in the season, and may themselves reproduce in the same year they were born.
There are no major threats to Northern short-tailed shrews at present.
According to IUCN, the Northern short-tailed shrew is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Due to their insectivorous diet, Northern short-tailed shrews play an important role in the ecosystem they live by controlling numbers of insects they consume. They are also prey items for such local predators as owls, trout, snakes, raptors, canids, cats, mustelids, skunks, raccoons, and opossums.