By RICK BORCHELT
Courtesy of Chiswick Chap
“Not a creature was stirring, not even a mouse.”
Wherever he was when he wrote his famous poem, “A Visit From St. Nicholas,” Clement Clarke Moore wasn’t in Maryland. Christmas Eve in our area is exactly when the mice are stirring — you can count on it!
Most of us have experiences with mice scouting out our pantries, shredding tissue paper to make nests in the sock drawer or leaving tiny brown pellet presents across the kitchen counter. These are the tell-signs of Mus musculus, the house mouse, once a wild mouse species from Eurasia that over the centuries has grown so closely allied to humans that it’s hard to find a truly wild population of these rodents anymore.
When the weather warms up in spring, a lot of these house mice move out into yards, gardens, woods, weedy lots and brush piles, enjoying the bounty of the land. But come the first frosty days of autumn, they’re scrambling to come back inside where it’s warm. That’s when you start finding their gifts in your kitchen cabinets and hear ominous scamperings inside your walls.
Ominous because, as the saying goes, for every mouse you hear or see, there are 10 more you don’t. That’s probably an exaggeration, but indoor mouse populations can explode in a hurry — mice become sexually mature at six to eight weeks of age, and females can have up to 15 litters, each with 7 to 10 pups, in the course of a year. Female mice can get pregnant again within 24 hours of giving birth.
Ominous also because of their toilet habits. In addition to the evidence of droppings, mice mark their territories, their routes to and from food and their nest, and every other place they go with a constant dribble of urine. If you dare, you can use a UV light to see these delicate pee pathways.
Mice can also carry hantaviruses, some of which cause lung infections while other strains are associated with renal failure. Hantaviruses infect humans who breathe in dust that has been contaminated by mouse urine or droppings. And like most mammals, mice can carry fleas, ticks and lice that also transmit various diseases.
Mus musculus (Mus is the Latin word for mouse) and people have a long history of cohabitation going back at least 10,000 years and perhaps as many as 15,000 years. Mice discovered that people tended to stay in one place and kept granaries — double jackpot for these grain- and seed-preferring rodents. But they aren’t the only mice that might be stirring during the winter holidays.
White-footed mice (Peromyscus leucopus) are the most common wild mice in our suburbs, often spending time not only on the forest floor but also in shrubs and even well up in trees. They are shy and seldom venture indoors except in the harshest of winter weather. They are equal opportunity foragers, eating seeds and roots as well as insects and other invertebrate prey. White-footed mice are so fond of spongy moth (aka gypsy moth) pupae in leaf litter that they probably keep the population of this invasive pest in check in many woodlands. In turn, they are frequent prey items for hawks, owls, shrews and foxes.
One local mouse you won’t see during winter is the meadow jumping mouse, Zapus hudsonius. A meadow, marsh, and field specialist, this mouse gets its name from its prodigious leaping abilities — up to 3 feet — aided by oversized hind feet and a tail much longer than its body that serves as a rudder for these long jumps. Like white-footed mice, Zapus is a seed, fruit and insect specialist. Unlike house mice or white-footed mice, meadow jumping mice hibernate for the winter. They won’t be stirring from mid-September or October until late March or April.
Of these three (not blind!) mice, house mice are most nondescript. Their fur is dull grayish brown, and their bellies and feet are buffy or light gray. The front legs and hind legs are about the same size. House mice have naked or sparsely furry tails noticeably shorter than their bodies, mostly the same grayish color overall. House mice belong to the family Muridae, the Old World mice and rats.
White-footed mice are a brighter chestnut brown, with large eyes and ears that stick up above the fur. They have hind legs that are just noticeably larger than their front legs. Their tails are longer than their bodies, furry and bicolored — dark on top and light on the bottom, with a distinct line separating the colors. Not only are their feet bright white, so are their bellies. Most people think they are objectively cuter than house mice.
Courtesy of Jim Stasz
White-footed mice are part of a larger group of about 60 species in the genus Peromyscus (from the Greek meaning “white-booted”). There is one other Peromyscus mouse in Maryland, the very similar deer mouse, which is found mostly in the mountain counties in the western part of the state.
Meadow jumping mice have small bodies but very long tails — almost twice as long as their bodies. Because they are active during the day, their eyes are smaller than those of either house mice or white-footed mice. Their ears are smaller, too, and are mostly hidden in the yellow-brown fur. The hind legs are very long, about half the length of the body, but the front legs are quite short, giving this tiny mouse a Tyrannosaurus rex sort of build. Jumping mice belong to the family Zapodidae, which includes one other species in far western Maryland, the woodland jumping mouse.
Here’s hoping the clatter on your roof this holiday is in fact St. Nicholas and not a family of mice in the attic!
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Have questions for Rick about the world of nature in and around the Maryland suburbs or suggestions for future columns? Drop him a note at rborchelt@gmail.com.
