Shrews are intriguing Minnesota mammals
They're neither mouse nor vole, yet they have features of both. They scamper about, they squeak, they're small, and they're furry. But strange as it is, these mouse-like creatures of the woods and farm are no more a rodent than you and I are. Indeed, what I'm talking about here is none other than the humble shrew; though, even with them, there's plenty of variability amongst the lot.
I've been inspired to think about shrews these days because of one particular uninvited guest. Having not so long ago rid the house of a string of deer mice, or so I thought, and thus claimed victory of all that is Rodentia, I discovered the error of my ways just last week while watching a not-so-interesting television program.
A brownish, pointy-nosed form skittering across the carpet along the wall underneath the bay window, helped shake loose the cobwebs from my brain. And though no one else in the room seemed to take note (of both my awakening and the new life form that I honestly believed I observed), I became convinced of my discovery when the slumbering dog perked up long enough and cocked his big head to the side while looking after the impossibly small creature as it darted across the carpet once more.
I surmised the little fellow to be a loner, although I concede it was possible that others of its kind might be around too. Yet, throughout the course of the evening it was he alone, and not another, that streaked from one end of the room to the other by negotiating the same identical route: from underneath the blue swivel plush rocker it would appear, and along the wall it'd travel, behind the television stand and the book shelves, and onto into the dining room it would go. A short while later, the same route again, only in reverse order.
Shrews, as it turns out, are more closely related to moles than mice. Both shrews and moles belong to the order Insectivora and are, accordingly, insectivores. Insectivores are believed to be the most primitive of contemporary living placental mammals. Astonishingly, the order Insectivora dates back 75 million years ago, to the Cretaceous period of North America. Occurring throughout most of the world, insectivores do not inhabit any parts of Antarctica, Australia, or Greenland. In all, some 375 species of the order exists.
As the name of their order suggests, species of the order are, by and large, insectivorous; that is, their diet consists of primarily insects. But as is with most creatures of the animal kingdom, plenty of exceptions exist amongst those that we humans have lumped into neat and orderly classification schemes. While the diets of the 10 species that reside in the north-central states are comprised of mostly insects, the palates of some shrews are diversely satiated.
The northern short-tailed shrew, for example, and the largest of our local shrews that can weigh up to 30 grams, is known to hunt, kill, and eat mice and voles. Amazingly, the saliva of the northern short-tailed shrew is actually toxic, a poison, or venomous to put it another way. One well-placed bite helps to subdue or kill larger prey such as mice and voles. Additional items on the menu, as is the case with other species of shrews, include invertebrates such as earthworms, centipedes, snails and slugs, beetles and bugs, spiders, as well as certain fungi and vegetable matter.
On the opposite end of the shrew-scale is the diminutive (and aptly named at that!) pygmy shrew. This little fellow at its heaviest tips the scale at a whopping four grams. This, I believe, is the suspect species of shrew that has taken a liking to my Becida abode. Generally too small to be taken by the conventional mousetrap, this miniature mammal, cute as it is, is more easily captured by glue traps or pitfall traps (small cans buried flush with the ground). An accomplished climber, I observed with interest one evening this very species of shrew perform one of its acrobatic stunts.
While I watched the pint-sized shrew dash across the floor and disappear behind the shelf sitting on the floor below a window covered by a floor-length drape, I began to notice the drape begin to move ever so slightly. To my complete surprise, I discovered the shrew negotiating the drape's vertical aspect with absolute ease. And what I learned next was equally as unexpected. Arriving at the window, the teeny titan paused to drink from the few droplets of condensation that had accumulated on the pane. Resourceful little rascal indeed!
Other Minnesota shrews include the arctic shrew, masked shrew, and water shrew. Whereas the arctic shrew inhabits a large range and occurs over most of Minnesota, Wisconsin, the U.P. of Michigan, and Canada, the masked shrew occurs over most of northern North America. The water shrew, another abundant shrew, lives out its life in and near water. Not only does this species swim and dive extremely well as it hunts for aquatic insects on the bottoms of streams and wetlands, they reportedly possess the ability to run short distances on the surface of water too.
Shrews are intriguing Minnesota mammals. Most are nocturnal and have poorly developed eyesight, but have exceptional senses of smell and touch. Quite vocal, in fact readily detectable to our own human ears, it's not unusual to hear their high-pitched squeaks on calm mornings or evenings in the woods underneath forest debris. Without question, shrews are yet another fascinating creature to appreciate as we get out and enjoy the great outdoors.