Shrewd

A brisk wind bit my cheeks as we hiked down the trail. Even bundled up in a puffy jacket and thick pants, with a wool hat on my head and jumbo mittens on my hands, I could not keep my nose and toes from getting cold. Three to four inches of snow crunched loudly under our boots. Most of the dimples in the snow were made from raindrops or tree-falling snow plops, but a few were made by wild little feet.

 

The daisy chain tracks of a grouse crisscrossed the trail like a holiday garland. Imprints from hopping squirrels connected trees like strings of lights. One trail decoration was slightly different. Marked by a subtle change in the color of the snow, it was simply a one inch thick line across the path.

 

Curious, I knelt down and poked through the snow with my fingers. They found a hollow beneath the icy crust. Sliding my fingers under the crust, following the two-finger-wide line of gray, I peeled the crystalline roof off a long, narrow tunnel. In the frozen slush on the tunnel’s floor were tiny footprints in a diagonal walking pattern.

 

Was this the secret passageway of a tiny forest sprite or snow fairy? The hallway of snow would certainly protect its travelers from the bitter wind that reddened my cheeks.

 

No, not a fairy, but this tunnel belonged to a forest sprite in its own right – a shrew. We have six species of shrews in Wisconsin, and they are all tiny. Short legs, a pointed nose, slender body, and small eyes and ears help shrews function at the interface between soil particles and plant debris. Here, they use their acute sense of smell and even echolocation to find food. This habitat is rich with their favorite prey: insect larvae, ants, beetles, crickets, grasshoppers, spiders, centipedes, slugs, and snails.

 

Shrews have an extraordinarily fast metabolism and digest their food very rapidly, so they must feed voraciously night and day. A shrew can only last a few hours without food, and must eat more than its body weight in a day. One species of shrew, the short-tailed shrew, has developed venomous saliva that can stun larger animals such as mice, rabbits, and cats. This allows them access to larger meals.

 

The venom may also help protect the short-tailed shrew from its many predators: larger shrews, owls, hawks, snakes, frogs, and fish. Large mammals like foxes, weasels, and bobcats, may kill and eat shrews, but often leave them on the ground, presumably because of the species’ strong odor. Deb Malesevich, Museum Director, told me a story about her indoor/outdoor cat, OhOh, projectile vomiting a shrew across the living room as Deb dived to catch it in a wad of paper towels. What does that tell you about the palatability of shrews?

 

Palatable or not, most shrews die within the first year, if not the first two months of life. We found one of those casualties outside the Museum’s back door just the other day. Whether death came by starvation or a predator, the result was the same. I carefully measured the body, tail, and hind feet to help me identify it as a masked shrew, Sorex cinereus, the most widely distributed shrew in North America. It is in a different genus than the short-tailed shrew, and is not reported to have a venomous bite.

 

As I examined the rigid, furry corpse I was astonished by its diminutive size and weight. Measuring less than four inches from nose to tail, and weighing less than a penny, it is amazing that this critter can survive a Wisconsin winter at all!

 

At that size, staying warm can be tough. The subnivean layer, where snow meets earth, stays at a relatively constant 32 degrees. While this may not seem tropical to you, compared to a -10 degree wind chill topside, it is a major improvement. Deeper snow means more insulation from the skyward elements, so I bet shrews love snowier winters, just like skiers.

 

[Why do YOU love winter? Send me your reason(s), your first name, and age, and they will be posted on a website, coming soon! You can also look forward to a new exhibit coming to the Museum in February: “We LOVE Winter!” about local animals and their adaptations to snow and cold.]

 

Along the trail, tracks grew indistinct and the wind picked up as the gray skies grew darker. On this cold winter afternoon, I would not have minded a calm, cozy tunnel myself!

 

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, STAR POWER: Energy from the Sun, opened in May 2012 and will remain open until April, 2013.

 

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.