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PECAN-BOWLING MICE

The old farmhouse at Hilton Pond Center for Piedmont Natural History doubles both as an office for the Center and a home for the Hilton family. The beautiful white structure--the first part of which was erected in about 1918--was designed with utility in mind. Bedrooms are off a wide, west-facing main hall that runs the length of the house, and if front and back doors remain open in summer, cool night breezes blow down it to draw fresh air through the windows of each room. The only problem is the 11-foot ceilings and polished hardwood floor make this "dog-trot" hallway a veritable echo chamber--great for singing along with sentimental songs from the 70s but not so conducive for sleep on dark winter nights in 2004.

All text & photos © Hilton Pond Center

Often, about when the clock tolls 2 a.m., a team of mice begins to assemble in the main hall for what must be the next round of competition in their World Indoor Pecan-Bowling Championship, during which these little rodents entertain themselves until dawn by repeatedly practicing their sport. They start by dropping jumbo pecans from the dining room table near one end of the hall and follow by dribbling and bouncing the hard-shelled nuts for more than 50 feet to where our bedroom door stands open. Some mornings when we arise before dawn a bare foot placed squarely onto one of those pecans produces a painful reminder of mice-capades the night before. Unless you've had the pleasure of hearing a mouse rolling pecans along a hardwood floor in the wee hours of the morning, you might not realize just how difficult it is to ignore such sound.

Each winter, a few of these pecan-bowling mice somehow gain access to the farmhouse interior and amaze us with their nibbling abilities. Dried beans, walnuts, cookies, apples, oatmeal bags, sugar sacks, and a variety of other foodstuffs suddenly contain holes and tiny tooth marks. When this happens, we put out live traps and banish each mouse we catch to the cornucopia of food scraps in the Center's outdoor compost pile, but reinforcements always seem to replace them--in increasingly greater numbers.

Tiny gnaw marks aren't the only evidence our cold-weather visitors leave behind, since their nibbling is accompanied by equally tiny black pellets. A tad smaller than rice grains (above right), these droppings are obvious signs of well-fed mice with efficiently-functioning waste elimination systems. City folks may have similar problems with nighttime invaders, but the rodent they encounter is more often the House Mouse, Mus musculus--an import from Europe that can literally infest dwellings, carry multiple diseases, and cause severe damage with its gnawing.

Our pecan-bowling friends at Hilton Pond, however, are always little Peromyscus mice that come in from the cold and leave in the spring when weather improves. There are many kinds of Peromyscus across North America, but the three most likely to be found in the Carolina Piedmont are P. humulis (Oldfield Mouse), P. leucopus (White-footed Mouse), and P. maniculatus (Deer Mouse). The latter has wide distribution across nearly all the continental U.S. and southern Canada, while P. leucopus occurs primarily east of the Rocky Mountains.

The Oldfield Mouse is smallest of these three; its diagnostic field mark--a whitish tail with a thin brown stripe down the middle of the top--makes it easy to identify. White-footed and Deer Mice, however, are essentially indistinguishable; both have white feet, so even professional mammalogists have difficulty telling live specimens apart. Some experts claim the species can be separated because the hind foot of the adult White-footed Mouse (above) is usually slightly shorter than that of a mature Deer Mouse, and because the tail of the White-footed Mouse is sparsely haired and not distinctly two-toned in side view (bottom photo). In South Carolina Deer Mice probably occur only in mountain regions, but skull features (below left)--or DNA analysis--apparently provide the only sure way to differentiate them from the White-footed.

The Cotton Mouse, P. gossypinus, further complicates field identification in the southern Piedmont, but it occurs primarily in the Sandhills and Coastal Plain.All our Peromyscus species have white bellies and brown backs, with juveniles and subadults (bottom photo) tending to be darker, grayer, and with dorsal fur that is less uniformly colored. There is considerable geographic variation in shade and hue of the adults. Peromyscus of any age have exceptionally long whiskers that--coupled with big ears and bulbous eyes--help them navigate the woods (and hallways) on the blackest of nights.

Peromyscus are generically called "field mice" and--in more natural habitats than the Hilton Pond farmhouse--consume huge quantities of seeds, insects, and succulent plant parts. (Within our office and lab they do perform a service by gathering up occasional stray sunflower seeds or corn kernels that we drop while filling feeders to hang outdoors.) These little rodents seldom reach more than 6 or 7 inches in length, including a 2- or 3-inch tail. Together, Peromyscus mice are probably the most common mammals in the Piedmont--in part because they are small and adaptable to variety of habitats, but mostly because they are amazingly fecund. Females bear one to seven young after a gestation period of only three or four weeks, and their offspring become sexually active within 60 days after birth. Heck, in any given winter we probably have three or four generations of mice prowling through the pantry!

With this kind of reproductive capacity, it's a wonder we aren't overrun by our various Peromyscus. Fortunately, their populations are held in check by local hawks, owls, weasels, foxes, shrews, snakes, and a number of other predators. In fact, these mice are an extremely important link in the natural food chain. Their one real drawback from a human perspective is that they are vectors for hantavirus and Lyme disease--neither of which are very pleasant for folks who contract such ailments. Despite this and their ability to damage stored foods, wool socks, and kitchen cabinets with their nibbling and nest-making, we would do well to appreciate all the various Peromyscus mice for their ecological significance and adaptable lifestyles.

Such appreciation, of course, need not extend to any athletically inclined little rodents that happen to go midnight pecan-bowling in old farmhouses at Hilton Pond Center or elsewhere in the Piedmont.

POSTSCRIPT: After we posted the above account, we got an e-mail asking if we hadn't exaggerated how many White-footed Mice invade the old farmhouse at Hilton Pond Center each winter. In response, we set a number of live traps for seven consecutive nights and caught 24 mice, all subadults and juveniles. Obviously these little rodents are thriving at Hilton Pond and far outnumber the human inhabitants.

NOTE: Be sure to scroll down for an account of all birds banded or recaptured during the week, as well as some other interesting nature notes.

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LITERARY NOTE: We often get inquiries about availability of The Piedmont Naturalist--Vol. One, 1986 by Bill Hilton Jr. The book is out of print, but a signed copy of this first edition is up for auction this week on eBay by a Texas bookseller. Auction closes late on 13 Feb 2004.