The View from Heifer Hill: A shrew is an expeditious beast
Gonna flame, gonna burn, take one quick turn
And be gone, like James Dean."
— Greg Brown
Somewhere not far from where you sit now, let's say within 100 yards, there is likely to be a fellow mammal with a heart racing at the speed of 20 beats per second and a respiration rate of 12.5 breaths per second (try it!). You can bet that animal is in motion, and that is will burn through life quickly. You might also bet that the animal is a shrew and that among the six possible species in our region, it is most likely the cosmopolitan short-tailed shrew. Shrews are renowned for their metabolic extravagance. A shrew that hasn't dined in the past few hours is in on the brink of starvation. One captive short-tailed shrew ate 170 percent of its body weight in food per day. If you weigh 150 pounds, you would need to eat 255 pounds of food in a day to rival that feat. Most species of shrew live just through the summer of the year after they were born. By the end of that time, they become elderly and lose their territories to young shrews. Short-tailed shrews have lived to the advanced age of 3 years.
If these creatures are so abundant and active, why are they so seldom seen? One reason is that they are primarily fossorial, which is a fun way of saying that they live underground. Further, shrews are often mistaken for mice or moles. Any tiny dark mammal you see that scurries at high speed is probably a shrew.
Shrews and moles make up the Order Insectivora. Among their shared characteristics are their subterranean habits, velvety fur, tiny eyes with little functional value, and very inconspicuous ears. If you have an adult shrew in one hand and an adult mole in the other — the shrew will be the smaller animal, and the mole will be the one with giant clawed flippers for front paws.
Shrews have many adaptations that aid them in their quests to survive and reproduce. To procure and protect the food they need, shrews are fiercely territorial. When a shrew encounters a trespasser, shrieks and fisticuffs ensue. Shrews are smelly little beasts, especially the males, and researchers believe scent-marking helps reduce territorial skirmishes and encourages females to permit the proximity of a male for the vital business of mating. Scientists have found that some shrew species navigate using echo-location. Short-tailed shrews, one of only two known mammals with toxic saliva, can paralyze or kill small prey with a nip. While invertebrates have the most to fear, even amphibians and small mammals must tremble when they encounter these fierce hunters.
My favorite feature of shrew morphology is the nose; shrews have long, pointed, muscular snouts that take a very active role in guiding these animals through life. One night, while sitting near a beaver pond, I placed a couple of small piles of sunflower seeds near my seat to see what I might lure in. I soon heard a rustling in the leaf litter, and the swiveling snout of a short-tailed shrew emerged. Once it detected the direction of the sunflower seeds, the entire shrew zipped from its lair, grabbed a seed, and dashed the 20 inches back again. The shrew repeated this act a few times, and then I heard a sound coming from within the soil that could only have been the sound of shrew teeth severing small tree roots. Within a few minutes, the little snout appeared again, this time right next to the sunflower seeds, which then disappeared one by one, a twitter of triumph marking each heist.
Shrews burn their way right through winter, scurrying through the subnivean zone, the crystalline realm beneath the snow. Occasionally they cross the snow surface. You might have seen their tracks on your winter outings. They are often mistaken for those of a mouse. Do they disappear into a tunnel the diameter of a pencil? You have seen the doorway of a tiny shrew.
Do you want to learn more about your miniature wild neighbors? Join me for a class on Friday, Feb. 28, the third in a series on winter-active wildlife. This one will focus on the small and speedy. Learn all about it at beec.org.
Patti Smith is a naturalist at the Bonnyvale Environmental Education Center. The View from Heifer Hill, a feature on the nature of our region, appears in this space the first Saturday of each month. She welcomes your feedback at Patti@beec.org.
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