The only venomous mammal in North America can be found here in Canada
When one thinks of venomous animals that might be lurking in the darkness, the furry and kind of cute northern short-tailed shrew is definitely not the type of creature that comes to mind.
However, this rare example of a venomous mammal — the only mammalian species in North America to possess venom — can be found right here in Ontario.
Not that we would suggest you go out looking for one.
The northern short-tailed shrew (Blarina brevicauda) may appear friend-shaped, but this furry little critter comes equipped with a potent venom that can paralyze and kill small animals and bring a world of pain to any unsuspecting human who gets too close.
Found in a wide range spanning from the Maritimes to the midwest, including all of Southern Ontario and the Great Lakes region, B. brevicauda typically makes its home in moist habitats with dense leaf or plant cover, but can also be found in areas of human habitation like household gardens.
These shrews are voracious eaters and are known to wolf down up to three times their own body weight in food every single day.
It subsists primarily on insects, invertebrates, and other small mammals, the latter of which are taken down with the help of B. brevicauda‘s unique (on this continent) venomous saliva.
Paul Reeves Photography/Shutterstock
The venom contains a kallikrein-like protease, a chemical similar to the serine protease found in the venom of dangerous snakes like vipers.
It is most similar to the toxin produced by the Mexican beaded lizard, and despite completely independent evolutionary paths, these toxins evolved from the same precursor protein, and their delivery mechanism is strikingly similar.
Both animals’ venom is secreted through ducts at the base of their jaws, flowing along grooves in the teeth and into their victims. Unlike the injecting venom of a snake, these animals will literally chew the poison into prey.
So, while the northern short-tailed shrew may look like a friendly weasel frolicking in the brush, it is more comparable to a toxin-drooling Komodo dragon than the mammals it shares its habitat with.
Prey unlucky enough to find itself on the receiving end of a northern short-tailed shrew bite will be quickly paralyzed or, in the case of smaller animals, killed outright.
But what happens if a human is bitten by one of these unassuming little creatures?
Well, most importantly, don’t panic.
B. brevicauda venom is of little medical significance to humans, beyond the painful experience caused by the combined bite and envenomation.
Reported bites — typically inflicted on individuals attempting to handle a shrew — have resulted in burning and significant swelling, though effects can be more severe for cats and dogs exposed to a bite.
So, if you see one of these critters in the wild, your best bet is to admire it from afar and steer clear of a potentially unpleasant bite.