Flattened Fauna, Revised

by Roger M. Knutson

  Thirteen-lined Ground Squirrels (Spermophilus tridecemlineatus)

  6 × 2 inches, with a 3-inch short-furred tail

  HABITS AND ABUNDANCE This, the most common road squirrel of the central U.S., is commonly called a “gopher.” These squirrels of the plains states are curious animals who will often stand up on their hind legs and stare at an approaching car before leaving the food that lured them onto the road (and often keeps them there for several days). Their varied diet consists of seeds blown off grain trucks, insects bounced off cars, and occasionally carrion already flattened by previous passersby. Their abandoned burrows can often be found at the edge of vegetation just off the road shoulder. When sufficiently flattened, they can leave the asphalt by “road drift” to the shoulder, where they will remain for several weeks in dry weather. The young, particularly abundant during late summer, are more commonly found on the road than adults. The gopher is a true hibernator and spends all the cold months in a state of suspended animation far from the road.

  FIELD MARKS AND RANGE Their body shape is nearly rectangular, with parallel sides for nearly the entire six-inch length. The numerous light-colored longitudinal lines and rows of spots on a tan-to-medium-brown body may be oriented lengthwise or diagonally, depending on the violence of the animal’s demise. They are found from Ohio to Wyoming, and from southern Canada to Texas.

  If the animal seen is about the same size as the thirteen-lined ground squirrel, but has the fewer stripes characteristic of the slightly smaller and less rectangular eastern chipmunk, it is probably a gold-mantled ground squirrel (Spermophilus lateralis). This common resident of the mountain states hangs around campgrounds and picnic areas. It is often seen decorating western roadways near high human-use areas. Any close association with people is likely to introduce an animal into the road fauna. Where there are people, there are fast-moving wheels and flattened squirrels.

  Thirteen-lined ground squirrel (Spermophilus tridecemlineatus), commonly known as a gopher

  No road mammal has the longitudinal extension of the thirteen-lined ground squirrel. You don’t need to count all thirteen lines; nothing else on the road has more than four lengthwise stripes, and only a snake is as long and narrow.

  Norway Rats (Rattus norvegicus)

  9 × 4 inches, with a 9-inch hairless tail

  HABITS AND ABUNDANCE Wherever people live, the equally adaptable Norway rat follows and establishes itself. It learns quickly and is probably more vehicle-shy than any other mammal; it seems to have lived with us long enough to appreciate the hazards of automobiles and trucks. Five or six litters in a single year and year-round breeding in all climates are characteristic: A single pair of rats can produce 1,000 descendants in a single year. Norway rats don’t generally live for more than a few months, but even so, numbers in any urban area can be in the thousands per block. We might therefore expect the highways passing through high urban concentrations to be nearly covered with flat rats, but such is not the case. This suggests that these rats have adapted to highways and people unlike any other animal in the guide. Rats are vastly underrepresented in any road fauna sample, even though they may be living under or even on the road. An individual or even a small family will occasionally take up residence in a larger car or truck and live on potato chip crumbs and discarded Big Macs, becoming the only member of the road fauna known to use vehicles for transportation. Young males wander for considerable distances and are the specimens most commonly seen on urban streets. These are one of the few flattened fauna members seen in parking lots.

  FIELD MARKS AND RANGE Norway rats are a uniform gray and present an elongated oval shape after a short time on the road or in the parking lot. Their size and hairless tail will distinguish them. All the rats native to this continent are somewhat smaller, have furrier tails, and are not likely to be found in urban locations. The Norway rat is never far from where people live. The smaller, more slender, and darker black rat (Rattus rattus) is confined to harbors and near-harbor urban areas, particularly on the south Atlantic and California coasts.

  Norway rat (Rattus norvegicus)

  This is a parking-lot rat, and an old one. Size, the visible dentition, and the hairless tail pinpoint the identification. Parking-lot animals can be examined at leisure, and features like dentition become significant on close scrutiny. Photocopy by Canon NP-350F.

  Tree Squirrels (Sciurus species)

  14 × 6 inches, with a bushy tail as long as the body

  HABITS AND ABUNDANCE While wooded areas in the countryside are home to large numbers of squirrels, long-settled urban areas provide nearly all the road specimens. Urban squirrels are almost totally unwary of human activity and pay a high price for their casual approach, especially the young ones. With the abundant nuts and fruits available in most urban areas and parks, many squirrels are so well nourished that they produce two litters per year, making the young animals likely to be reduced to two dimensions abundant almost year-round. The young are most active in June and October, especially in the latter month, when in addition to learning to feed themselves they begin to store food for the winter. Adult males are most likely to become part of the road fauna in January and June when they regularly chase females for hours at a time. Often several males will chase a single female, and their minds are certainly not on traffic patterns. Natural selection may operate clearly here, as the slowest male is most at risk. As one naturalist puts it, “The trailing male is clearly on the paving.” Population eruptions and mass movements involving hundreds of squirrels have been reported only rarely. Here, too, the squirrels appear to not be concentrating on safety, and may be found flattened by the dozens in a single mile. Squirrels are crepuscular (most active at dawn and dusk), which in many seasons put them on the road at the busiest times. They have a sufficiently keen sense of smell to find acorns under a foot of snow, but this sense is useless when it comes to moving objects.

  FIELD MARKS AND RANGE Color and pattern vary both within and between species, and the color variation is most dramatic in urban populations, from the pure white squirrels of Olney, Illinois, to occasional black ones. Most are nearly uniform tan to red or brown, with somewhat lighter underparts. A nearly uniform patch of appropriately sized fur with a long bushy tail will almost always mark a road squirrel, even if no other features are discernible. The tail remains free of the road and waves conspicuously in the slipstream from passing traffic. The squirrel is one of the few mammals that shows much movement on the road.

  Tree squirrel (Sciurus species)

  Squirrels present about equally in lateral or dorsi-ventral positions. The tail is never folded, and an average of three legs should be visible on any road specimen.

  One or another of the species of Sciurus, or their near relatives Tamiasciurus (including the Douglas squirrel of the Pacific Northwest and the northern red squirrel of the northern U.S. and Canada), is found all across the U.S. wherever trees are available. The grey squirrels (Sciurus carolinensis) and fox squirrels (Sciurus niger), most common on the residential streets, are found mostly in the eastern half of the country. Members of transplanted populations of both species appear on roads near parks and parklike areas on the West Coast.

  Muskrats (Ondatra zibethicus)

  12 × 8 inches, with a 12-inch hairless tail

  HABITS AND ABUNDANCE The muskrat never feeds on the road, but is present in large enough numbers in spring and fall to be near the top of anyone’s road species list. It eats marsh plants (with the exception noted below), and as part of the road fauna, will most likely be found by marsh-bordered roads. However, during spring and fall it migrates long distances between marshes and may be found anywhere, including garage driveways in large cities. The period of dispersal is longer and more pronounced if muskrat populations are high, and under favorable conditions a pair of muskrats can become two dozen in a single season. With high population levels and competition for food, cannibalism is a real option for muskrats, and many of the younger muskrats would apparently rath
er be Chevettized than cannibalized. The young are often driven out of the marsh by older muskrats at about six weeks of age, when they must attempt to find new homes—often a spot on the highway or even a place in the suburbs. They are comfortable with humans and human activities and may be found in large numbers even in cities, if marshy land with standing water is available. Their usual response to perceived danger is to dive in and swim away under water. On land they are much more aggressive, but on the road this is a fatal character flaw.

  FIELD MARKS AND RANGE The muskrat has a thick, strong, darkly furred pelt. The animal holds together well and assumes a nearly constant shape on the road. The short front legs are seldom obvious (now and then a back foot may be visible; see silhouette, below), the back feet are webbed, and no neck or ears are visible. The usual shape is a near-perfect oval, slightly pointed on the head end, with a long, flattened tail. The color is uniform over the oval and varies from reddish to dark brown.

  Muskrat (Ondatra zibethicus)

  A prime muskrat pelt is one of the more durable and dependable items on the road. Most muskrats, regardless of their status at initial impact, develop rapidly into the nearly round silhouette shown here. Only an opossum, which is more elongated on the road, could be confused with a road muskrat. The muskrat’s webbed feet determine the diagnosis and should be easily identifiable to a biker or hiker.

  Muskrats occur in every state except Hawaii. Along the Gulf Coast and in coastal Washington and Oregon, what looks like an overly large muskrat on the road may be a nutria (Myocastor coypus), a sometimes abundant Argentinean import that has escaped captivity and established itself in marshy locations. It has a more obvious neck and a more nearly square road form.

  Opossums (Didelphis virginiana)

  20 × 12 inches, with a 12-inch hairless tail

  HABITS AND ABUNDANCE Contrary to popular southern opinion, opossums are not born dead by the side of the road, but may give that impression in places where they are abundant. The opossum often forages on the road and may briefly benefit from the varied diet available there. It will literally eat anything, including its relatives who were feeding on the road a few days earlier. In their off-road habitat, opossums are too tough to kill easily (serious reports suggest that they are immune to rattlesnake venom), and many a dog has mauled or left for dead an opossum that went on its way once the dog departed. But on the road the opossum’s toughness may work to its disadvantage. Becoming limp and lying there with an open mouth after a near miss by the first car may serve to put off a dog or coyote, but stands little chance against even compact cars. Such behavior is surely fatal on the road, where lying down quickly becomes a permanent condition. There is often not enough time to play dead before becoming dead. A nocturnal activity pattern and a fascination with approaching lights also serves to increase the road opossum population. Even without cars, usually opossums live for no more than two years, which is not enough time to learn much about traffic patterns. Nomadic males less than a year old are particularly common on the road. Overall, the opossum is the most abundant mammal of its size on the road, by virtue of its ability to adapt to nearly any surroundings and a tendency to stand and fight when confronted.

  FIELD MARKS AND RANGE Since early times of European settlement in the U.S., the opossum has spread from its original southeastern home to the Canadian border, and now is found in all but the mountain states of the West. It was introduced in California in 1870, and thrives there in association with human activities of all kinds. Opossums do not hibernate and, in more northerly parts of their current range, winter opossums may display severely frostbitten ears and tails even before they settle onto the road. The opossum is as likely to be found in urban as rural environments. In urban areas it will raid garbage cans to get the varied diet it prefers. According to Tom Torgerson of Eureka, California, a serious, longtime student of the California road fauna, a road opossum looks like a cat that stuck its paw in a light socket. It is almost the size of a house cat and does present a scruffy appearance, due to its long, grizzled hair. The road shape is a nearly uniform oval even after a few passes from an eighteen-wheeler. It tapers at one end to a hairless foot-long tail, and at the other to a pointed, whiskery snout. Its color is a nearly uniform gray with some longer white-tipped hairs. Individual color varies from nearly white to the rare cinnamon opossum.

  Opossum (Didelphis virginiana)

  The light color and elongated shape distinguish the opossum from its near road relatives. The hairs spread out in all directions on the road.

  Woodchuck (also called groundhog) (Marmota monax)

  18 × 12 inches, with a 9-inch bushy tail

  The largest of the ground squirrels is one of the few animals whose habitat has been enhanced by human activities. Naturalists describe woodchucks as “edge” organisms. Clearing the forests in the eastern half of the U.S. for agriculture and civilized pursuits has created new edges and new habitat, much of it right on the edge of roads and highways. The woodchuck is much more common now over its geographic range than it was in colonial times. There are several western species of Marmota, but they are mostly restricted to high altitudes and are extremely rare on the road.

  HABITS AND ABUNDANCE Considering the numbers and their usual proximity to roadways, woodchucks are underrepresented in the road fauna. They have excellent eyesight, forage only during daylight hours, sleep most of the time, hibernate for six months of the year, never travel far from their burrows, and have reasonably good speed afoot. However, their typical times of foraging coincide closely with daily rush hours, and the young tend to be uninformed about speed limits and road hazards. The elders usually drive the young out of the paternal burrow at the end of summer, by that time having had enough of five or six kids underfoot in cramped quarters. Most adult woodchucks are totally solitary in habits (except for a brief breeding season) and extremely aggressive toward other woodchucks, although they will flee from automobiles. Over the northern part of their range, they hibernate throughout the cold months and are never found on the road at that time. In early spring, however, they may venture onto smooth surfaces, looking for a clear shadow of themselves. The shadow and the silhouette are similar (see this page).

  Woodchuck (Marmota monax)

  Woodchucks on the road are nearly all dorsi-ventral in presentation. The chuck on the left demonstrates the spring appearance after a winter’s hibernation, and looks much like the shadow you might expect to see on February 2nd. The one on the right shows what summer eating will do for your silhouette.

  FIELD MARKS AND RANGE The woodchuck is heavy bodied and short-legged, usually presenting an almost square appearance. The color is a nearly uniform brown to yellow brown, and somewhat grizzled—the coat has long guard hairs with light-colored ends. The feet are dark to almost black. Most roadchucks are larger than a squirrel and smaller than a badger or raccoon. Fall roadchucks are considerably wider than early summer specimens, since they store large amounts of fat for winter hibernation. Most of the chucks seen on the road in late summer are more square than rectangular, with their dark feet barely visible at the corners.

  Woodchucks are common over the eastern half of the U.S. except for the southeast coastal plain; they are absent from Florida and Louisiana.

  Cottontail Rabbits (Sylvilagus species)

  16 × 16 inches

  HABITS AND ABUNDANCE The habits of rabbits do not bring them often to the road, but sheer numbers assure that they will be abundant among the road specimens. A good habitat off the road may have as many as ten rabbits per acre, and an outstanding stretch of road may have three to four per mile (see world record in Chapter 1). During 1936 and 1937, the cottontail was the second most abundant mammal on Iowa’s roadways, exceeded only by the thirteen-lined ground squirrel. The cars and trucks of the road habitat are just another predator in the life of a creature that seems almost designed to be killed and eaten. Young rabbits are produced in very large numbers and are especially obvious on the road in late spring and
early summer when their lack of experience makes them particularly susceptible to all predators. The cottontail is extremely fast over short distances and is able to cross a traffic lane in one or two exceedingly fast leaps. Unfortunately, it moves about mostly from dusk to dawn, and its usual first response to danger is to freeze and remain motionless. On the road, when the danger has passed, the cottontail is likely to remained permanently immobile. In general, it depends on lack of movement and protective coloration to save it; and neither works well on the road. Only approximately 10 percent of new rabbits survive the first year!

  Cottontail rabbit (Sylvilagus species)

  The cottontail presents a clear and obvious denial of the superstition that a rabbit’s foot brings good luck. Many of the road forms show at least three feet and no luck at all. Legs and ears are both easily visible in all of the usual presentations.

  FIELD MARKS AND RANGE The name provides the most valuable single field mark. If you see a generally gray form of appropriate size with a white spot at one end and one or two three-inch ears visible at the other, it is most likely a cottontail. The various species found all across America are nearly identical in their road presentation. The Atlantic coastal forms are a bit darker and the Southwest desert species lighter, but the ears and tail are constant. The cottontail is a year-round road resident over all of its range, with the winter forms lasting much longer than the summer ones because of the cooler temperatures.

  Armadillos (Dasypus novemcinctus)

  17 × 12 inches, with a 15-inch tapered tail

  HABITS AND ABUNDANCE The armadillo is nearsighted, has poorly developed hearing, and moves about mostly at night—a set of characteristics guaranteeing that relative to its numbers off the road, it will be better represented in the road fauna than any other mammal. Near-sightedness works well in locating the worms, grubs, and caterpillars that provide most of its food, but is of little help in helping the armadillo look both ways before crossing the highway. This creature also has a very fine sense of smell, but cars at 60 to 70 mph leave scent only behind them, never before. The armadillo is generally unaware that any vehicle is approaching until it is very near, and then the animal’s startled response is to leap straight up into the air, usually to about bumper height. Armadillos can run with considerable speed, but they seldom make use of this skill on the road. A near miss by a passing pickup is likely to call forth the other response to disturbance—to curl up in a tight ball, with only the thickly plated back exposed. While this might puzzle a fox, it is no problem for an Audi. When severely hounded, the armadillos alternative response is to dig in—not useful on the interstate. This unaggressive, bumbling creature has few natural enemies except motorized vehicles.