When B movies feature dangerous mammals, they’re usually hulking beasts (often feline or canine) with massive fangs and sharp claws that rip and tear their way through crowded city streets or sleepy northwoods hamlets.
Hulking and massive, however, are the polar opposite of how we might describe Maryland’s arguably fiercest mammal. It’s barely two inches long, but comes packed with a mouthful of needle-sharp teeth that deliver a venomous bite capable of quickly dispatching its prey. That’s good, because it’s also a ravenous creature that needs to eat its weight or more every day just to stay alive. Anything near in size to this Lilliputian predator is fair game, from insects and earthworms to voles and mice and even others of its kind.
This fearsome furball is the shrew.
In the DMV, that toxin-toting midget monster would be the northern short-tailed shrew, Blarina brevicauda. The origin of the genus name Blarina is lost to etymological history, but brevicauda fittingly translates as short (brevi-) tail (-cauda). Northern short-tailed shrews are the most widespread shrew in Maryland — its full range extends from the Gulf states into Canada.
True shrews are tiny, pugnacious tubes of energy packed into a silky felt pelt. Worldwide, there are some 350 shrew species (members of the taxonomic family Soricidae), making them the third-most-diverse group of mammals on the planet, second only to rodents and bats. While they superficially look like mice, shrews are actually more closely related to bats and moles.
Indeed, shrews share some physical characteristics with moles — reduced eyes with poor vision, short legs, short tails — but with one striking exception: Shrews have excellent hearing. Like bats, they find prey by echolocation. Shrews emit high-pitched squeaks like bats do and use the echoes that bounce back to triangulate the location of their victims.
Maryland can lay claim to eight members of the broader shrew family, but only one venomous shrew. In our area you can find the least shrew (Cryptotis parvus), masked shrew (Sorex cinereus) and southeastern shrew (Sorex longirostris), all of which have tails at least half again as long as their bodies. Brevicauda tails, in contrast, are only about a third of the body length.
The venom of northern short-tailed shrews is a complex chemical cocktail very closely related to some snake and lizard toxins. When this shrew bites, the toxic brew dribbles out along a grove in the shrew’s front teeth. Nevertheless, this venom is powerful stuff: One northern short-tailed shrew possesses enough at any given time to paralyze (and ultimately kill) up to 200 mice. And that venom is powerful enough to result in a painful (but not paralyzing) injury to any human who might want to fondle a little fuzzy friend.
The high metabolism and energy demand of these little fireballs mean that winters are especially hard on shrews, given their high metabolism and energy demand; 90% or more of them can die during a harsh, long season. They forage almost constantly, 24/7, while temperatures are tolerable and cache any surplus food for leaner times. When winter sets in, they spend more of their time underground, where temperatures are moderate. They also build insulated underground nests to ward off the chill and can generate body heat (without shivering) by drawing on special fat they store in their bodies. In a pinch they’ll eat seeds, roots and nuts. Some shrews, but apparently not northern short-tails, can enter a state of torpor similar to hibernation when the weather is cold and prey is scarce.
Burning the candle at both ends comes at a lifespan-cost for shrews, which typically only live for about a year. Their short life means they have to breed early and often to maintain their populations. A female shrew is ready to mate again within a day of giving birth and can be suckling one litter while pregnant with a second, all the while foraging furiously to keep herself going. Shrews are fiercely territorial; females quickly send both their mates and offspring packing.
Shakespearean allusions notwithstanding, northern short-tailed shrews are not likely to be tamed anytime soon. The use of the word shrew to refer to women of a particularly waspish demeanor dates back even earlier than The Bard, apparently reflecting the disposition of the equally vicious (but nonvenomous) common shrew (Sorex araneus) of Europe.
Shrews, including our resident Blarina, are creatures of varied habitats from woodlands to meadows to roadsides, as long as there is water available. They’re even surprisingly common in suburban yards and gardens, where they can sometimes be spotted darting across flagstones or scurrying along a flower border. Unfortunately, however, you’re more likely to see a dead shrew than a live one, usually one that starved to death during a cold spell.
It’s probably the first time in its life this shrew has ever slowed down.
Rick Borchelt is a botanist and science writer who writes and teaches about gardening and natural history. Reach him with questions about this column at rborchelt@gmail.com.