The smallest four-legged predators on the tundra are shrews but they certainly are by no means the most timid. Shrews are insectivores, the most primitive order of placental mammals and here in Alaska we have 9 representatives. They are found in a variety of habitats, both moist and dry, but they are rarely seen because they inhabit a network of runways under the ground cover.
Most shrews feed on insects and other small invertebrates, (unless you have chocolate or dog food in handy places in your home during the winter). They eat more than their own body weight in food every day and vary their diet with other shrews, mice, earthworms if available or meat in a cache. Their hunting technique seems to be a constant darting about until they run into prey, which is identified by smell, since they have poor eyesight but acute hearing and sense of smell. They have a long snout, beady eyes, and short grayish- brown fur that almost hides their ears. Their tiny tracks are distinguishable from mice by their five-toed feet, mice generally have four toes on their front feet.
The most common shrew in Alaska is the Masked or Common shrew (Sorex cinereus) which ranges across the northern Lower 48, Canada and all of mainland AK. Its body is about 2 inches long, its tail up to 2 inches and a large one may weigh one-fifth of an ounce. Musk glands emit a powerful odor which can deter some predators, however, birds of prey will take them as do arctic grayling.
The northern water shrew (Sorex palustris) hunts on the bottoms of lakes and streams and ranges across Canada and into Southeastern and Southcentral Alaska. A shrew eats as much as it does to fuel its high metabolic rate. Its heart beats 700 times a minute, up to 1,200 when frightened, and it breathes ten times in the time it takes a person to inhale and exhale once. This high metabolic rate is due partly to shrew¹s small size. All warm-blooded animals use most of the energy they take in to maintain a constant internal body temperature. Smaller animals expend more energy than large animals, and therefore, need to eat more to replace lost body heat. Some species of shrews will starve to death in a matter of hours without food. Its no surprise that they are active both day and night. But it surely is a wonder that any of them can last through an Alaskan night.
