Shrews: short-lived and sassy
Have you ever seen a shrew? Chances are good that the answer is no, given their secretive nature and relatively brief life spans of approximately 18 to 20 months.
Although they resemble very small mice, and are also mammals, shrews belong to the order Insectivora. As the name implies, they feed primarily on insects, but have high metabolic rates that require them to eat frequently, evidenced by their average heart rate of roughly 1,200 beats per minute.
Shrews are tiny but tenacious predators that sometimes attack animals larger than themselves—including other shrews—and supplement their insect intake with worms, slugs, snails, moss, seeds and sometimes carrion. Most shrews are small enough to fit in a tablespoon, one of the characteristics that distinguishes them from moles, voles and mice. Other features are their long, pointed noses, conical slender skulls and tiny beady eyes. They are fierce predators, relying primarily on their sense of hearing and smell, as their barely visible eyes are thought to be of little use. Shrews secrete an offensive oder, often leaving them untouched by predators even after death.
Shrews may be out and about during the day or night, but are especially active at dusk. The small creatures typically burrow through leaf litter and often use the tunnels of other animals including mice, making them a challenge to observe. They tend to prefer a wooded habitat that also features rocks, fallen trees, grassy areas and the transitional zones of water bodies ranging from swamps to boggy ponds and lakes.
According to the Pennsylvania Game Commission, there are seven shrew species in the state—the smallest being the pygmy shrew which ranges in length from 3.2 to 3.8 inches and in weight from 0.08 to 0.13 ounces. Others include the short-tailed shrew, the long-tailed shrew, the smoky shrew, the masked shrew, the water shrew and the least shrew. Most are similar in appearance and may require the input of an expert for accurate identification.