The northern short-tailed shrew (Blarina brevicauda) is the largest shrew in the genus Blarina,
Description
thumb|Northern short-tailed shrew
This shrew has a total length of , of which is tail; and weighs . The species exhibits slight sexual dimorphism in size, with the male being slightly larger than the female. though one record from the late Pliocene (Blancan land mammal age) is tentatively attributed to this species. Another source indicates the earliest record of the genus Blarina is a specimen of B. b. talpoides, from the Blancan (early Pleistocene) in Kansas. The species is thought to have arisen in the middle or late Pliocene. The B. b. brevicauda subspecies appeared later.
Range
This shrew is found throughout central and eastern North America, from southern Saskatchewan to Atlantic Canada and south to northern Arkansas and Georgia. It is probably the most common shrew in the Great Lakes region. This shrew consumes vertebrates more often than other shrews do. The shrew mostly forages within a few hours after sunset, though it is also active during cloudy days.
Toxin
The saliva of the northern short-tailed shrew contains a kallikrein-like protease, used to paralyze and subdue its prey. The toxin is strong enough to kill small animals, up to sizes somewhat larger than the shrew itself, and results in painful bites to humans who attempt to handle the shrew. The venomous saliva is secreted from submaxillary glands, through a duct which opens at the base of the lower incisors, where the saliva flows along the groove formed by the two incisors, and into the prey.
Epidemiology
Northern short-tailed shrews in Alabama have been identified as carriers of the newly-discovered Camp Hill virus that is not known to cause disease but which is distantly related to Nipah virus. "Researchers at an Auburn University lab collected" the shrew, according to a news report, "that was found with a new species of henipavirus named after the Alabama town where the specimen came from".
Physiology
Senses
Their sense of smell is thought to be poor, and their eyes are degenerated and vision is thought to be limited to the detection of light, Other winter adaptations include the creation of a lined nest which aids the shrew in conserving heat, the caching of food in case of prey shortages, foraging below the leaf litter or snow where the temperature is milder, and decreasing activity levels during cold periods. Along with these behavioral adaptations, the northern short-tailed shrew increases its ability to generate body heat during the winter by nonshivering thermogenesis in brown adipose tissue.
Behavior
Other shrews spend more time above ground than does the northern short-tailed shrew, which prefers to tunnel along below ground, through the leaf litter, or at the snow/ground interface.
Reproduction
Mating occurs from March through September, though most births occur early or late in that period. During copulation, the male and female are locked together, and the female drags the male along with her. Gestation lasts 21–24 days, and after birth, the six to eight young are suckled for up to 25 days before the babies are weaned.