Owls Aren't Wise and Bats Aren't Blind (8 page)

There are other differences between the two species, as well. For example, the northern flying squirrel molts twice a year, shedding its fur in May or June, and donning a heavier winter coat in September. The tail, however, only molts once, in early summer. The southern flying squirrel, on the other hand, molts only once, in September.

There are also differences in reproduction and nesting habits. Northern flying squirrels usually have only one litter a year—an eminently sensible system, considering the all-too-brief summer throughout much of this squirrel’s range. They breed in late winter and, after a forty-day gestation period, give birth to between two and five blind, naked young.

In contrast, southern flying squirrels usually have two litters a year throughout much of their range—one in the period from February to May, the second from July to September. The dual litters reflect the much longer warm season available to the southern flying squirrel, which takes full reproductive advantage of this climatic benefit. After a forty-day gestation, they give birth to tiny, naked, blind young, each weighing less than one-quarter ounce.

As in the majority of mammals, male flying squirrels of both species do nothing to help raise their offspring. The females, however, are excellent mothers that defend their young and are known to move them to a new nest if parasites become too abundant in the original nest.

Living quarters and winter habits for the two species also vary. In summer, the northern flying squirrel builds summer nests, usually close to the trunk of an evergreen tree. In winter, however, they reside in tree cavities, often enlarged from the prior labors of woodpeckers.

In far northern climes, these squirrels often hollow out growths known as witches’ brooms. These peculiar masses are caused by a fungus that sometimes infects spruce and balsam fir trees. The fungus causes the tree to grow a dense, tangled maze of tiny branches that somewhat resembles an old-fashioned broom—hence the name. This hollow in a witch’s broom, after being heavily lined with grass, feathers, or other soft material by the enterprising occupant, is evidently warmer than a tree cavity lined with soft material.

Flying squirrels of both species are quite sociable in winter, and as many as eight northern flying squirrels of the same sex may share winter quarters, providing warmth for each other in the den. In extremely cold weather, northern flying squirrels semihibernate, often sleeping through several days until the weather moderates.

Southern flying squirrels also build summer nests, although these are leaf nests in hardwood trees such as oaks and hickories. Although they remain active all winter, and eschew the occasional semihibernation of their cousins, southern flying squirrels are even more social than their northern counterparts when it comes to communal winter quarters. Twenty or more have been known to occupy the same winter home, and one observer reported that
fifty
southern flying squirrels shared a single tree cavity in Illinois!

Although flying squirrels generally make little noise, they can vocalize, though the sounds are a bit different for each species. The northern flying squirrel emits low chirps and sometimes makes little clucking sounds when upset. The southern species, on the other hand, twitters, chirps, and utters high-pitched sounds sometimes described as “tseets.”

As might be expected of small, largely defenseless creatures, flying squirrels of both species are a target for a wide variety of predators. Owls of various sorts are a major predator; according to one Alaska biologist, a pair of nesting northern spotted owls can cause the demise of as many as 440 flying squirrels in a single year.

Hawks are also listed as a predator of both species, but if flying squirrels are indeed totally nocturnal, as some sources indicate, it seems inconsistent for those same sources to list the completely diurnal hawks as their predator. However, this inconsistency aside, hawks probably do catch an occasional flying squirrel from those that now and then forage in daylight hours.

Far more serious predators than hawks abound, however. Weasels, martens, fishers, foxes, coyotes, raccoons, snakes, and bobcats all take their toll. That leaves one more important predator, at least where humans live— the house cat.

I can personally testify to the efficacy of these small felines when it comes to catching flying squirrels. Until it unfortunately burned, there was a very large barn on our farm. Built in 1866, it was forty-five feet wide, seventy feet long, three stories high, and was full of hollow partitions and a multitude of nooks and crannies. An amazing assortment of wildlife inhabited that barn, including flying squirrels.

Although we never saw a live flying squirrel in the barn, we often found evidence of their presence. Our house cats regularly prowled the area, sometimes during daylight hours and sometimes at night. Often when we entered the barn we would see the tails of squirrels that the cats had killed and eaten. The majority of them were from red squirrels, but it was by no means uncommon to find the soft, silky tails of flying squirrels—mute testimony both to the abundance of the squirrels and the predatory prowess of the cats.

It’s perhaps appropriate to mention that two subspecies of the northern flying squirrel are considered endangered, according to the U.S. Fish and Wildlife Service. One is the Carolina northern flying squirrel
(Glaucomys sabrinus coloratus),
which is found in just five locations—three in western North Carolina and two in eastern Tennessee. Its closest relative is the other endangered subspecies, the Virginia northern flying squirrel
(Glaucomys sabrinus
fuscus);
this latter is found in just a few areas of Virginia and West Virginia.

While we hope that these two endangered subspecies survive, we can also take comfort from the fact that both the northern and southern flying squirrels are generally doing quite well throughout the major part of their respective ranges. Despite the attrition from disease and a horde of predators, the little gliders are sufficiently elusive, and have a high enough reproductive rate, to ensure their survival.

5

A “Pig,” Perhaps, but Not a Hog: The Porcupine

MYTHS

Porcupine quills are barbed.

Porcupine quills are filled with air, like a balloon.

Porcupines can throw their quills.

A porcupine is a hedgehog.

Porcupines are adept at climbing trees.

THE PORCUPINE IS A CURIOSITY, AN ODDITY, ONE OF THOSE ABERRATIONS DECIDEDLY OUT OF THE MAMMALIAN MAINSTREAM. Slow, plodding, awkward, rather dim-witted, and quite lacking in adaptability, the porcupine would seem to qualify as a poor candidate for survival in a dangerous world where so many seemingly better-equipped animals have passed into extinction. Yet despite such numerous disadvantages, this walking collection of anomalies has survived for millions of years and gives every appearance of wending its bumbling, unconcerned way into the distant future.

The saving grace in this oddball animal’s makeup is, of course, its quilly armor. Without that wonderful evolutionary quirk, the porcupine would long since have gone the way of dinosaurs, woolly mammoths, and sundry other unfortunates. However, the porky’s defenses are so formidable that, with few exceptions, it can waddle its way through life with minimal problems from would-be predators.

Porcupine quills are actually highly specialized hairs, totally distinct from the short underfur and very long guard hairs. A porcupine has an astonishing 30,000 quills to protect its back, flanks, and tail—an average of about 140 quills per square inch on much of its body! The face and underside lack quills, however, thereby giving porkies the animal equivalent of an Achilles’ heel, albeit one that few predators are able to take advantage of.

Porcupine

The quills vary in length; those on the back are the longest, while the shorter ones are located on the head and tail. The longest quills can span as much as five inches, but most measure about three inches. The majority of quills are white for much of their length—possibly to make the porcupine’s weapons highly visible and hence more threatening to a prospective predator—but a few are completely black. Each quill has an extremely sharp tip and is very loosely attached at its base; it hardly takes more than a touch to embed the sharp point in the flesh of an attacker, whereupon the quill easily departs from its very tenuous attachment to its owner.

It’s widely believed that porcupine quills are equipped with tiny barbs, like those on a fishhook: they aren’t, although for all practical purposes they might as well be. Instead, the tip of a quill has diminutive scales, much like tiny fish scales. These overlap so that the raised edges point toward the rear and function in much the same manner as the barbs on a fishhook; once embedded in flesh, these scales make it very difficult and painful to remove a quill. In any event, to the animal or human painfully stabbed by a number of these miniature lances, the technical difference between barbs and scales is probably of no consequence!

Because of the scales, lodged quills tend to work their way forward. There are numerous instances, in both humans and animals, of quills that have disappeared, worked forward, and, after a period of time, emerged at a considerable distance from the entry point. Occasionally, quills have been known to work their way into a vital organ and cause death. This is probably relatively rare, however; a greater danger is that an animal whose face and mouth are riddled with quills may be unable to hunt or eat properly, and thus may die of malnutrition.

One myth about porcupine quills stems from the fact that their hard, tough exterior conceals a more or less hollow interior. The operative term here is “more or less.” Folk wisdom to the contrary, quills aren’t filled with air like a balloon, and hence don’t deflate when their posterior end is cut off. Instead, quills are filled with light, spongy material, and cutting the end of the quill off is no aid to removing it from a dog or other creature. Indeed, this tactic may even make matters worse, since it leaves less quill to grip with pliers or forceps, and may splinter the quill as well.

Undoubtedly, the oldest, most enduring, and most widely believed myth about porcupines is that they can throw their quills. Just when and how this fiction began is buried in the mists of time. However, it most certainly was given great credence by that famous Roman, Pliny the Elder, who died in the cataclysmic eruption of Vesuvius that buried Pompeii and Herculaneum in A.D. 79.

Pliny’s massive, thirty-seven-volume
Historiae Naturalis XXXVII,
published in A.D. 77, is riddled with scientific inaccuracies—men whose feet were turned the wrong way, winged horses, unicorns, and many other nonexistent marvels. Evidently, Pliny was an uncritical believer in the wide variety of fanciful tales that reached his ears, and one of these concerned the porcupine. In 1601, Englishman Philemon Holland, also a true believer, gave us this translation: “The porkpen hath the longer sharp pointed quilles, and those, when he stretcheth his skin, he sendeth and shooteth from him.”

Perhaps the porcupine’s formidable tail has something to do with this myth. When an intruder approaches a porcupine too closely, the animal reacts by lashing its tail ferociously from side to side. One quick flick from that spiky caudal appendage, and the unwary can find themselves with a horde of quills driven deep into their soft flesh. While this clearly isn’t a case of throwing quills, it might seem that way to a victim of the tail’s rapid swipes.

Although porcupines lack the ability to throw their quills, they do have the capacity to raise and lower them at will. When threatened, a porky elevates its quills so that it bristles like some sort of mammalian cactus with giant spines. Shakespeare was evidently aware of this trait. In
Hamlet,
the ghost of Hamlet’s father says, “I could a tale unfold whose lightest word . . . would freeze thy young blood . . . make thy knotted and combined locks to part, and each particular hair to stand on end, like quills upon the fretful porpentine.”

Although not quite as quaint as Holland’s “porkpen,” this is yet another interesting and—to us moderns, at least—amusing variation of the porcupine’s name. Regardless of old-fashioned spellings, the derivation of this walking pincushion’s name is as intriguing as the creature itself: it descends from Italian
porcospino,
meaning “spiny pig” (
porco
= pig +
spino
= thorn or spine). Evidently some Italian or another thought that the porcupine either resembled a pig in some fashion or was related to it. In any event, the
spino
was properly descriptive, even though the
porco
missed its mark by a wide margin, and the name stuck.

Far less appropriate is the term
hedgehog,
by which the porcupine is widely known. A hog it is not, nor does it frequent hedges. Wholly unrelated, except by virtue of being mammals, the porcupine and hedgehog bear little resemblance other than the highly superficial characteristic of a spiny exterior.

For openers, the porcupine is a rodent, whereas the hedgehog is an insectivore. Then there is the matter of size: while porcupines are rather hefty animals, the hedgehog is diminutive—only about ten inches long. Even in the matter of their defensive weaponry, the two species are more divergent than might appear at first glance. The spines on the hedgehog, although sharp enough to give it good protection when it curls into a tight ball if danger threatens, are hardly the lethal weapons of the porcupine’s detachable quills.

Why, then, did the North American porcupine come to be widely known by the misnomer “hedgehog”? The first English colonists in North America were quite likely unfamiliar with porcupines except from literary references, since Old World porcupines are absent from Great Britain and most of Europe. These colonists had a penchant for calling unfamiliar creatures by the names of familiar ones from “back home,” and in a prickly sort of way the porcupine bears at least a superficial resemblance to the hedgehog, a common denizen of English hedgerows.

Regardless of names, accurate or otherwise, the porcupine’s arsenal of quills is so formidable that most predators quickly learn the desirability of giving the porky a wide berth. A variety of predators may occasionally kill a porcupine: these include bobcats, bears, cougars, wolves, coyotes, and wolverines. However, after one or two painful encounters, these predators emerge sadder and a great deal wiser in the ways of porcupines. The single exception seems to be the domestic dog; while some dogs learn to shun porcupines after one or two episodes, others never seem to learn.