The Arctic shrew is most distinctive in its tri-colored fur. It is dark brown or black on its back from its head to the base of its tail, while its flanks are a lighter brown, and its underside is lighter still grayish brown. Even its tail is bi-colored, dark brown on the dorsal side, and gradually fading to a lighter brown on the ventral side. The fur is grayer in wintertime, and its tricolor is most marked during the winter months from October to June, for the fur is thicker and brighter. Arctic shrews molt twice a year, and the tricolor bands in the fur are less prominent in younger shrews.
Arctic shrews are native to North America, ranging from the Arctic Circle in the north and as far south as the northern United States, into North and South Dakota, Wisconsin, Michigan, and Minnesota. Their eastern limits are in eastern Quebec and the Atlantic Maritime provinces, and their western limits are the southern Yukon and Mackenzie valleys. These small animals live in areas near bodies of water, such as lakes, streams, marshes, wetlands, bogs, swamps, ditches, or open areas near wetlands. Arctic shrews can be found in clearings in boreal forests, and occasionally in mixed conifer swamps, dry or old fields, dense grasses near ditches, mixed grasses, in the undergrowth of forest clearings, alder thickets, and dry marsh with grasses, sedge hammocks, forbs, cattail, willow, and red-osier shrubs.
Arctic shrews are solitary territorial animals. They are active during the day and night. Arctic shrews are very active and move quickly. Periods of inactivity are spent lying on the ground, either on one side or with the ventral side down, body rolled up, and head tucked under the body. They also groom themselves by wiping the forefeet rapidly along the mouth.
There is little information about the mating habits of the Arctic shrew; however males of most shrew species mate with many females, and compete with other males for females, so the assumption is that Arctic shrews behave similarly. In Wisconsin, the breeding season lasts from February to August, and the breeding season is shorter in more northern areas, from April to August. Females give birth to one or two litters each year, and these litters range in size from 4 to 10 offspring, with an average of 7 offspring per litter. The gestation period ranges between 13 and 21 days, so the young stay with their mother until 5 to 6.5 weeks after conception, and males make no contribution to parental care. When they are born, young Arctic shrews are helpless. Their mother cares for them until the end of the weaning period, 20 to 24 days after birth. Both female and male Arctic shrews reach reproductive maturity after one year.
Arctic shrews do not face any major threats at present.
According to IUCN, the Arctic shrew is 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.