I misspoke already, it should read, “Skiing and Shrews.”  Twice this month I have encountered shrews while cross-country skiing.  Once, in the moonlight, skiing on the groomed tracks at Apex, a tiny dark blur marred the white landscape.  The shape was unmistakably shrew-like, and the tiny mammal ran across the groomed trail, up and down the tracks, even trying to hide beneath my skis when I stopped to watch him.  All shrews are comparatively small, most no larger than a mouse. But the smallest is the Etruscan Shrew (Suncus etruscus) which at about 3.5 cm and 2 grams is the smallest living land mammal.  Eventually he disappeared as suddenly as he had appeared.  Upon closer inspection, we, for another skier has stopped to appreciate this natural history moment with me, found a tiny coin-sized hole in the snow that must have been the shrew’s run.  We speculated that he was out and about, and when he came back to his hole, he just couldn’t find it at first… perhaps because we were standing between him and his lair.

Of course I had to do some research on shrews, but not until I found another shrew in the snow.  This time I was skiing on the un-groomed rail trail at Cottonwood Lake.  There in the tracks, or rather, below the tracks I saw a suspicious looking dark speck in the snow.  Snow had been falling for days, and the only other dark specks on the ground were pine-cone bits from feeding birds.  I backed up and dug my fingers into the snow, pulling out a tiny, frozen form.

I held the little grey shrew to my fact, listening and feeling for movement.  Finding non, I put her in my pocket.  Skiing along, I kept imagining her waking, stirring, sticking her frightened little head out of my pocket, wondering what was going on.  I know some animals, like frogs, can freeze solid and survive, waking upon thawing.  I guess it was too much to hope that maybe shrews could do that too.  It all comes, I suppose, of being warm blooded.

I’ve learned  a lot about shrews these past few weeks from the library and Wikipedia.  I will always thank my professor at Oregon State University though, for villifying the shrew for me, as he compared it to the timid vegetarian voles.  Shrews, unlike voles, are not rodents and do not eat grains or plants at all.  Shrews look somewhat like long-nosed mice, but are more closely related to moles.  They are classified in the order Soricomorpha and have sharp, red-tipped teeth, not the flat gnawing teeth of rodents and rabbits.  They have small eyes, and poor vision, but have excellent senses of hearing and smell. They are very active animals, with voracious appetites and unusually high metabolic rates. Shrews must eat 80-90 % of their own body weight in food daily.

Shrews are also one of the most diverse and abundant mammal families, following rodents and bats.  It seems that their diversity stems from recent periods of isolation caused by ice events, where warming and cooling temperatures caused shrews to form isolated populations which then became distinct species.  This is the commonly held hypothesis as to why there are so many similar looking and acting shrews, especially in North America.  But while many different species of shrews may be found in a few square kilometers, each will inhabit a slightly different micro-habitat, some specialize in climbing trees, living underground, living under snow or even hunting in water.

Shrews do not hibernate, which is why I found two in the snow.  They are, however, capable of entering torpor. In winter, some species may lose between 30% and 50% of their body weight, shrinking the size of bones, skull and internal organs.

But shrews are even cooler than that!  Shrews hold nearly 10% of their mass in their brain, which is the highest brain to body mass ratio of all animals (including humans).  Then there’s the poison – some species of shrew are venomous.  The shrews venom comes through grooves in its teeth to enter the body of its prey.  The American short-tailed shrew contains enough venom in its body to kill 200 mice!

The Northern Short-tailed Shrew is known to echolocate!!

As if the tiny shrew doesn’t have enough surprises, they can also echolocate!  I know.  Bizzare and amazing.  Besides bats and marine mammals, The only mammals known to echolocate are shrews and the tenrecs of Madagascar. The shrews emit series of ultrasonic squeaks. In contrast to bats, shrews use echolocation only to investigate their habitat rather than to pinpoint food. Except for large objects, such as a big stone or tree trunk, they will probably only receive information on habitat type from the overall call reverberations. This might be comparable to human hearing whether one calls into a beech forest or into a reverberant wine cellar.

Sources:  Wikipedia and Mammals of the Canadian Wild