I was working at my computer last week when some hurried activity outside my window caught my attention. An ivy-covered stone wall stops about 18 inches from the base of a large poplar tree at the edge of the woods that surround my house. I have a small squirrel feeder located about eight feet up the trunk of the poplar. Juncos and other birds scratch around in the feeder, knocking corn and sunflower seeds to the ground.

As I watched the area between the stone wall and the tree, leaves and litter would suddenly erupt like someone was shooting a blast of compressed air. As I studied this phenomena more closely, I could detect a flash of gray as some creature appeared to ricochet between the wall and the tree.

I focused my binoculars on the area between the tree and the wall. As I watched, the gray streak would stop for a fraction of a second at the base of the tree, grab a sunflower seed or kernel of corn, then turn and blast away for the wall, where it disappeared in the tangle of ivy. It was a short-tailed shrew, Blarina brevicauda.

One of the most common North American mammals, the short-tailed shrew is seldom seen in its natural habitat. When seen, these small (3 to 5 inches) slate gray creatures are often mistaken for mice or voles, but they are not rodents.

Shrews, along with moles, compose the most primitive order of placental mammals living today, Insectivora. There are about 290 species of shrews in the family Soricidae. The determination that this was a short-tailed shrew (B. brevicauda) and not a southern short-tailed shrew was based solely on range maps. The two were once thought to be one species, but have since been split by taxonomists. Habits and habitats of the two are basically the same, but they appear to have distinct ranges. The two would be nearly impossible to differentiate in the field.

The short-tailed shrew is one of the few venomous mammals and a ferocious predator. While the venom is not dangerous to humans, it almost instantly paralyzes the shrew’s prey and can be fatal to mouse-size creatures within 3-5 minutes. Shrews feed primarily on invertebrates like earthworms, slugs, grubs, snails and insects. It will also take small vertebrates like mice, small snakes and small birds. Some plant material is also consumed. They appear fond of an underground fungus, endogone. Berries and other vegetation (like free sunflower seeds and corn) are often consumed during the winter.

They have been known to cache sunflower seeds in captivity. But these nervous high-energy creatures are not suited to captivity. Shrews have the highest metabolism of any mammal in North America. Their heart rate has been measured at more than 700 beats per minute, and shrews in captivity have been known to die from the shock of loud noises. This high metabolism is one thing that makes them such fierce predators. They normally consume from half to twice their body weight in food each day.
These fossorial (underground) creatures create elaborate networks of tunnels, where they hunt and live. While most of these burrows are just beneath ground, some may reach a depth of 20 inches.

The short-tailed shrew has tiny eyes and very poor vision. Its ears are hidden under the sleek gray fur. It maneuvers through the maze of tunnels using its sensitive snout and whiskers and a type of echolocation. The short-tailed shrew is primarily nocturnal and/or crepuscular but can be seen foraging on cloudy days.

The highly territorial short-tailed shrew is unique among shrews and other mammals in the fact that it mates for life. The female builds a nest of shredded leaves and grasses beneath a stump or log. The mating season for these year-round creatures runs from March to September and most females have two litters comprised of 5 to 7 pups. The young generally leave the nest by three weeks and are weaned shortly thereafter.

Many predators avoid shrews because of strong scent glands used to mark their territory. Owls, hawks, snakes and weasels, however, are known to feed on shrews. Although there are records of short-tailed shrews living more than two years, most, in the wild, do not make it a year.
(Don Hendershot can be reached at don@smokymountainnews.com)

 

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