Critter Corner No. 34 – The Short-tailed Shrew by George Sly

Goose Pond FWA often hosts creatures that attract special attention. There are the annual visits of sandhill and whooping cranes for example. Deer and upland game seasons draw hundreds of hunters to the area. The arrival of long-distance migrants such as the shorebirds and the biannual influx of waterfowl attract scores of wildlife watchers.

But there are other animals that live here year-round and, though they lack the star power of some species, they play an essential role in the day-to-day ecology of the property. The short-tailed shrew is one of them.

Indiana is home to six species of shrews, all are tiny, secretive, mouse-sized mammals that are easy to overlook. They are related to moles and, in fact, shrews are sometimes mistaken for baby moles.

The short-tailed shrew is one of our larger shrew species. They average about four inches in total length. Their fur is velvety and silvery gray to black in color. Like other shrews in North America, they have chestnut-colored enamel on their teeth. This trait is due to iron in the tooth enamel which gives additional strength, quite useful for a voracious eater such as the short-tailed shrew. It has a very high metabolic rate and may eat nearly its own body weight in food each day. Much of its activity is spent darting helter skelter in a never-ending search for prey.

Short-tailed shrews occur in a variety of habitats. At GPFWA they may be found in areas as diverse as grasslands, oldfields, brushy fields, or the wooded, reclaimed strip-mined land on the northern edge of the property. This ability to use varied habitats helps to make them plentiful. J.O. Whitaker, Jr., in his Mammals of Indiana – A Field Guide, states that this shrew and the white-footed mouse are likely the two most abundant mammals in the state.

The major foods of the short-tailed shrew are centipedes, crickets, earthworms, caterpillars, snails, and slugs. This species can be active at any time of the day but, based upon the abundance of their skulls in owl pellets, are primarily nocturnal.

Short-tailed shrews are often taken by cats that roam free but are seldom eaten. They have small musk glands on their sides which make them unpalatable to the felines. Dogs and foxes may also catch them but likewise find their taste disagreeable.

These fascinating little mammals possess two traits of particular interest. Since their eyes are quite small and somewhat degenerate, they are left with poor vision. Their highly sensitive snout and whiskers help compensate for this. But, even more unusually, they use echolocation. By sending out high-pitched ultrasonic clicks—much like bats—they can navigate through the obstacles within their home ranges.

They also possess another adaptation which is quite rare among mammals; they are venomous. The toxin is a modified salivary enzyme produced in their submaxillary glands. The venom is introduced as the shrew chews its prey and is highly effective in immobilizing the small invertebrates it consumes. A 2009 article in the journal Current Biology describes the venom as similar to that of the Mexican beaded lizard (a relative of the Gila monster).

Some have wondered whether their bite might affect a human. A 1973 paper by biologist Howard Krosch (Journal of the Minnesota Academy of Sciences) sheds light on this question by describing the rather startling effects of a short-tailed shrew bite he suffered. (https://digitalcommons.morris.umn.edu/cgi/viewcontent.cgi?article=1453&context=jmas)

So, once again, we’ve met a common GPFWA resident that is easily overlooked—or even unknown—to many visitors. With its unusual adaptations and hectic life, the short-tailed shrew deserves more attention than it gets. Beyond its peculiarities, it plays a meaningful ecological role in controlling insect and other invertebrate populations.

The shrew also forms an important food web component. They are preyed upon by birds of prey such as barred owls as well as diurnal raptors like the red-shouldered hawk. The short-tailed shrew is one more small but vital thread in the intricate web of life that defines the Goose Pond ecosystem.