Little Brown Bats

little brown bat in a crack on the side of a house

The Guest House portico bat in 2007

Living, as we do, in an old country house, we often hear strange noises.

On an August evening, my husband Bruce and I sat in the living room reading. Shortly after 8:00 p.m., we heard unusual sounds coming from either the kitchen or sitting room.

We looked up at each other and then resumed reading. Both of us were engrossed in our books and didn’t feel like moving.

After all, many times we had investigated a noise and found nothing.

Then, there were more noises.

“I hope it’s not a bear,” I whispered to Bruce, remembering an attempted bear and cubs break-in back in June. “We’d better check it out.”

Because it was a wet night, it was already dark, and we couldn’t see a thing until Bruce switched on the sitting room lights. Then we ducked as a bat circled the room, narrowly missing the plates on our seven-foot-high plate rail.

Bruce opened the veranda door, but the bat continued its circling flight inside. As the minutes passed, I worried that mosquitoes, which had earlier driven us from the veranda, might get into the house.

But the bat was probably scooping up any that dared to enter and paid no attention to our feeble attempts to herd it out the door.

location of the bat in the previous photo

Location of the bat in the previous photo

Twice the bat barely missed the open door and once it landed for a few seconds on the wall, giving us a good look at its lustrous brown fur, but mostly it kept circling at plate rail height.

Bruce and I moved closer, he on one side of the door, I on the other, and I ducked reflexively every time the bat neared my head, even though I knew that its echolocation ability would keep it from hitting me.

Finally, it swooshed through the open door, and we breathed a sigh of relief. I was also elated that at least one little brown bat had escaped the white-nose syndrome (WNS), a fungus that has killed at least 95% of little brown bats throughout eastern North America since February 2006 when the disease was first discovered in a cave in Schoharie County, New York.

This cold-loving fungus Pseudogymnoascus destuctans only affects hibernating cave bats, which include the already Federally-Endangered Indiana bat, as well as the State-Threatened eastern small-footed bat, big brown bat, eastern long-eared bat, and tri-colored bat, but the little brown bat, also called little brown myotis, common bat, and cave bat, along with the eastern long-eared and tri-colored bats, is especially susceptible to the disease.

Dee Ann Reeder, A Bucknell University professor who has been studying bats in her bat vivarium even before the disease appeared, has been trying to understand how bats are affected and has been using little brown bats as her test subjects.

In a two-year captive study, she found WNS affected female little brown bats more than males and that bats kept in colder temperatures survived longer than those in warmer temperatures.

Little brown bats hibernating at Woodward Cave in central PA, February 2006

Little brown bats hibernating at Woodward Cave in central PA, February 2006

Reeder has worked closely with Greg Turner, PGC’s Endangered and Threatened Mammals Section Supervisor, to try to mitigate the disease, but this fuzzy white fungal growth around a bat’s muzzle, ears, and wing membranes thrives in winter hibernaculums—natural caves and old mines in Pennsylvania, such as the gated Hartman Limestone Mine at Canoe Creek State Park.

Back in 2008, when the PGC conducted its biannual count of bats at that mine, there were thousands of healthy, hibernating, mostly little brown bats. Three years later, they counted 38 total bats. And other hibernaculums throughout the state also contained few live bats.

Because bats cluster together in winter hibernaculums, the disease spreads easily from bat to bat. WNS causes them to rouse every few days instead of every few weeks as they used to do. The small size of little brown bats means they have less fat reserves to begin with so they quickly lose their fat reserves and starve.

They also lose more water through evaporation, and when they emerged, starved and dehydrated, for instance, from the Hartman Limestone Mine, they ate snow. In addition, little brown bats have suppressed immune systems during hibernation, which makes them more vulnerable to the fungus. Thus, once nicknamed the common bat, they are now rare.

Hibernating bats among the stalactites in Woodward Cave

Hibernating bats among the stalactites in Woodward Cave

Scientists say the best case scenario would be a full recovery of the bat population in 200 years! As of April 2015, the cave bats in 26 states and 5 Canadian provinces have been infected with WNS and still the disease rages westward at a frightening pace.

This is a huge wildlife disaster, certainly the worst in my lifetime, and all because some cavers, probably from Europe, where cave bats have evolved with the disease, brought the fungal spores over on their clothes.

Lately, there have been a few bright spots in this dismal picture. In 2014 the Hartman Limestone Mine cave bat count was 155, and this year 71 bats. Although the numbers are still low, according to Greg Turner, bats are coming into hibernation heavier, even the few juveniles, and they have fewer skin lesions on their wings. They also spread themselves out in hibernaculums. But all such changes may be due simply because there are few bats left to compete with for food and space.

Knowing all this, I welcomed our little brown bat visitor. One bat eats between 800,000 and 1 million insects a year including moths, wasps, gnats, midges, beetles, mayflies and especially mosquitoes, scooping up prey with its wings while flying or grabbing prey with its mouth.

Little brown bats have both day and night roosts during spring, summer and early fall. They like to roost near ponds, lakes, rivers or streams in buildings or trees, under rocks and woodpiles, and in caves. Females and their young occupy warm nursery roosts in natural hollows, buildings, such as old churches, at Canoe Creek State Park, for example, and attics.

A bat on the side of a concrete block

A bat on the side of a concrete block outside our barn, 2007

They sleep almost 20 hours in a 24 hour cycle, saving their energy for when insect prey is most abundant—from dusk to two to three hours later and again for a shorter period before dawn. Flying at between 13 and 22 miles an hour, they hunt their prey using echolocation, a process in which they orient themselves by emitting high-frequency sounds and then interpreting the reflected sound waves.

They mate in autumn before hibernation, but fertilization occurs after the females emerge from hibernation the following spring. After a gestation period of 50 to 60 days, a single pup is born to a female in late May or early June.

Born with their eyes closed, the young hang in the nursery roost while their mothers hunt for food. The rest of the time, for two weeks, they cling to their mother’s nipple until they are two weeks old. At three weeks of age they learn to fly, and a week later they are adult-sized—between 3.1 and 3.7 inches with a wingspan of 8.6 to 10.5 inches.

Female little brown bats are larger than males, but all adults need to eat half their body weight each night, and new mothers more than their body weight. One study in New Hampshire of pregnant and nursing mothers found that they ate 7 insects per minute.

Before WNS, we could sit out on our unscreened veranda even after dark and rarely see or hear a mosquito. A few male little brown bats roosted in our barn and in openings under our roof and the guesthouse portico roof. We often watched them flying over our field and imagined them scooping up water from our stream.

Close-up of the little brown bat in the previous photo

Close-up of the little brown bat in the previous photo

Now the mosquitoes force us inside every evening. Farmers, who may not have realized how many harmful insects bats eat, will be forced to use more pesticides.

Little brown bats have few predators, although occasionally a snake, raccoon, skunk, or cat may enter a hibernaculum and kill a few. They’ve also been caught on barbed wire fences or in burdock bristles.

Before WNS, humans wiped out entire cave or attic nursery populations, but bat education by dedicated people such as Cal Butchkoski, a wildlife biologist for the PGC who spent countless hours at Canoe Creek State Park and other venues, presenting excellent programs on bats, and Environmental Educator Heidi Mullendore at the park who organized several successful Bat Festivals there, had begun to change peoples’ minds about bats. The PGC had also gated many vulnerable winter hibernaculums throughout the commonwealth.

Now it is illegal to kill even one bat of any species. With 6 million gone, “every bat we find is precious and needs to be conserved,” Dee Ann Reeder says.


All photos by Dave Bonta.

Amazing Hooded Warblers

Hooded warbler singing by JanetandPhil

Hooded warbler singing (photo by JanetandPhil – CC licence)

It’s a hot, humid day in mid-July, and a hooded warbler sings his clear, whistled “ta-wit, ta-wit, ta-wit, tee-yo” song. Because hooded warblers have one of the loudest and clearest of warbler songs, it can be heard a long distance, which may be why I can hear it despite a slight hearing loss as I age.

But hooded warbler song is tricky. Individual males have their own version of songs, especially the first several syllables. I’ve learned to listen for the last “tee-yo,” which I hear as “wee-zu” to identify them. This works most times unless a male decides to sing another version that rises in pitch at the end and, to my ear, sounds totally different from his usual songs.

At least hooded warbler song is distinctive, unlike the “buzzy” songs of some warblers. Hooded warblers also have a distinctive look that they keep throughout the year. The black hood, for which they are named, encircles their bright yellow head like a monk’s cowl.

Even the females have a trace of that hood or, at the very least, a black spot between their bill and their eyes. Those eyes are unusually large and dark, larger than 32 other warbler species.

Their breasts and bellies are also bright yellow and their backs and tails yellow-olive. They frequently flick those tails showing white outer tail feathers, which is still another identifying characteristic.

Best of all, when many fall migrating warblers have exchanged their flashy spring and summer feathers for dull fall and winter ones, hooded warblers remain their black-cowled, yellow-bodied selves.

Hooded warbler female by Joby Joseph

Hooded warbler female (Joby Joseph – CC licence)

Seeing these warblers, though, is not easy because they are understory skulkers, often feeding on or near the ground. They also nest close to the ground in shrubs and saplings.

Called “forest dependent gap specialists” by Dr. Bridget Stutchbury, who has studied hooded warblers extensively at her Hemlock Hill Research Station in northwestern Pennsylvania, Stutchbury writes in The Second Atlas of Breeding Birds in Pennsylvania that singing hooded warblers are most abundant in deciduous forests and breed in tree-fall gaps where sunshine encourages thick undergrowth.

Unfortunately, hooded warblers are also attracted by logged fragmented forests, and so are brown-headed cowbirds. In one study, by Stutchbury’s student, Margaret Eng, over half the hooded warbler nests in fragmented forests had cowbird eggs, and, as Stutchbury writes in her excellent book, The Bird Detective, “nesting success was so low that their fatal attraction to partially logged areas was actually driving the population numbers down…”

Despite this, though, hooded warbler numbers in Pennsylvania have increased an amazing 71% between the first and second atlasing projects. This is partly due to the expansion of their core range in western Pennsylvania, especially the northwest, as well as in Pennsylvania’s Ridge and Valley Province.

Like several other bird species, such as Carolina wrens and northern cardinals, hooded warbles are a southern species moving steadily north into New York state and Ontario. Scientists are not certain why, but Stutchbury says that “maturation of forest, combined with a possible response to climate change, may be important factors.”

Hooded warbler nest by Richard Bonnett

Hooded warbler nest (Richard Bonnett – CC licence)

Certainly, here on our mountaintop Ridge and Valley Province home, I hear and see more hooded warblers than I used to. Last summer I heard them along Laurel Ridge Trail, beside the Far Field Road, and along Greenbrier and Ten Springs trails, all forest areas with a shrubby understory.

Hooded warblers return to our mountain from the last week in April to the first in May, and we count as many as seven during our participation in the Pennsylvania Migratory Bird Day count the second Saturday in May. The males arrive first and occupy the same territory they had the previous year by chasing off intruders.

Females settle on a territory and mate shortly after arrival, favoring males that sing four to seven songs per minute. Possibly this signals to a female that such males will be strong enough to feed their young the average thousand times they deliver food during the raising of one clutch of young hooded warblers. According to Stutchbury, hooded warblers that sing less are more likely to have unfaithful mates. In fact, one-third of female hooded warblers have offspring fathered by a neighboring male.

The females choose nest sites in shrubs or saplings seven to 63 inches from the ground, although 25 inches is the average. It takes females two to six days to choose a site and build an open cup nest woven of soft inner bark, grasses, and plant-down with an outer wrapping of dead leaves, some of which hang down and camouflage the nest.

In Pennsylvania, blackberry, beech, black cherry, and prickly gooseberry are favorite nesting plants, but maple leaf viburnum, white ash, black and blue cohoshes, sugar maple, wild rose, yellow birch, hawthorn and hemlock are also used. All are native trees and shrubs. However, the only hooded warbler nest I ever found was in a thicket of nonnative Japanese barberry off Greenbrier Trail.

Here in Pennsylvania, first nesting attempts range from May 10 to June 11, and the second nesting from June 21 to July 19. Last summer on July 20, a hooded warbler distraction-displayed as I passed a thick understory of barberry, multiflora rose and blackberry, and I assumed a second nest was hidden within those prickly shrubs.

Hooded warbler on nest by USFWS

Hooded warbler on nest (USFWS – public domain)

The females incubate an average of four white eggs spotted with brown that look very much like those of brown-headed cowbirds. In northwestern Pennsylvania 62% of hooded warblers nests were parasitized by cowbirds, Stutchbury reported, possibly because cowbirds are attracted by chipping calls female hooded warblers make as they construct their nests. Usually cowbirds lay one or two eggs in a nest and remove one or more hooded warbler eggs at dawn before female hooded warblers arrive to lay their egg for the day.

After 12 days, the young hatch, and both parents feed them spiders and insects, the usual fare of hooded warblers, although only the females brood them.

At eight to nine days of age, the young fledge and can fly two to three days later. The parents divide up the fledglings and continue feeding them until they are five to six weeks old. But usually males take over the entire brood of fledglings if the females start second broods.

The males sing from the time they arrive until they leave for their wintering grounds in Central America. I’ve heard a male singing here as late as September 24, although peak migration time in Pennsylvania is from the fourth week in August to the second week in September.

Hooded warblers defend territories on their wintering grounds, but males prefer mature forests and females scrub, secondary forests and disturbed habitat, which is the first documented example of habitat segregation.

Male and Female hooded warbler by Louis Agassiz Fuertes, 1917

Hooded Warbler by Louis Agassiz Fuertes, 1917

Our son, Mark, who has lived off and on in Honduras over the years, has seen many wintering hooded warblers in shrubby areas and says they are always with Wilson’s warblers, a boreal breeding species that resembles a female hooded warbler except for the black cap of the male Wilson’s warbler.

Back in spring of 2010, Stutchbury attached tiny geolocator tags on the backs of five male hooded warblers to find out where they spend their winters. These tags record light levels and location information every two minutes and are now being used to track numerous songbird species.

A year later two of the five tagged hooded warblers returned to their territories in northwestern Pennsylvania, and Stutchbury and her team caught them in mist nets and analyzed the data. One male had flown south to the Florida panhandle, across the Gulf of Mexico and spent the winter in Nicaragua. In spring, he flew up to Mexico’s Yucatan peninsula, across the Gulf of Mexico, and up the Mississippi River Valley back to his exact same territory—altogether a 4,200 mile round trip.

When males return to their same 1.2 to 1.8 acre-territories, they use their long-term memory to identify nearby territories by the distinctive songs of the neighboring males. This minimizes the struggle for territory as they countersing with their neighbors and await the arrival of the females.

In the words of Samuel F. Rathbun, who studied the hooded warbler in west-central New York state early in the last century, “it is essentially a carefree song, musical, and often spiced with a little jauntiness, which in many ways perfectly reflects the actions of the bird.”

Hooded warbler by Paul Hurtado

Hooded warbler (Paul Hurtado – CC licence)

Blue Canaries

indigo bunting by Matt Stratmoen

indigo bunting — photo by Matt Stratmoen (CC licence)

On an early May morning, I step outside and hear a warble of clear, bright, musical notes. The indigo buntings have returned. Also known as “blue canaries” because of their color and song, I’ve never been able to describe indigo bunting song to others except to say that I know it when I hear it.

Other folks have had more success or perhaps a better ear. Arthur A. Allen, a prominent Cornell University ornithologist back in the 1930s, described it as “sweet, sweet, where, where, here, here, see it, see it,” and when I listen to its variable song on the Cornell Laboratory of Ornithology’s website (the Lab was the brainchild of Allen’s), his description seems apt. But the Lab website cuts Allen’s description down to eight words instead of ten—“what, what, where, where, see it, see it.”

indigo bunting resting on an outdoor table

indigo bunting resting on an outdoor table — photo by Dave Bonta

In fact, both descriptions are correct. That’s because a male indigo bunting has one complex song that combines 6 to 8 kinds of notes in different sequences. Furthermore, that choice of notes in his song is unique to what ornithologists call a “neighborhood” of indigo buntings, i.e. anywhere from 3 to 4 up to 22 males in adjacent territories that average 3 acres. And males living approximately a mile and a half apart have different songs which they develop from a repertoire of about 100 notes.

Unlike many songbirds, indigo buntings do not learn their songs from their fathers during their natal year. Instead, as first year males 80% of them match the song of neighboring males while 20% appear to learn their song somewhere else before settling on their own territory. Once they establish themselves, indigo bunting males sing 200 songs an hour at dawn, one song per minute the rest of the day, and they sing well into August.

The brilliant Prussian blue males with wings edged in black are often described as a piece of the sky come down to earth and like the sky, which only appears to be blue, their feathers merely refract and reflect blue light. The only pigment their feathers have is melanin. This gives them a brown-black color that is obvious if you hold a feather so that the light comes from behind instead of toward it as we usually see the bird. For this reason, male indigo buntings look more black than blue in poor light.

The females, who do most of the work of raising young ones, are mostly brown with lightly streaked breasts and are often mistaken for sparrows. Like the males, they have silver-gray conical bills, but while the males perch on the highest point in the shrubby, overgrown fields they favor, belting out their songs, the females stay hidden, sitting on open cup nests they have woven in shrubs or saplings.

Courtship is short, and females settle on a male’s territory a day or two after arriving. She chooses the nest site in fields or the edges of woods, railways or roadsides, in shrubs, such as blackberries, gray dogwoods, multiflora roses, and staghorn sumacs, in goldenrods and nettles, or in sapling trees such as black locust, aspen, elm, black birch or maple. Usually she builds the nest 1.5 to 3 feet above the ground but sometimes as much as 10 feet later in the season. Nest materials of soft leaves, grasses, stems and strips of bark are held together by weaving and by wrapping the nest in spider webs, and grasses and sometimes deer hair line the nest.

indigo bunting nest by Richard Bonnett

indigo bunting nest — photo by Richard Bonnett (licence)

Then she lays 1 to 4 white eggs on subsequent days and begins incubating them after the last egg is laid. It takes from 11 to 14 days, depending on the weather, for her eggs to hatch. Once her chicks arrive, she broods and feeds them small insects, spiders, and berries, as much as 54 times a day with breaks averaging 16 minutes for very young nestlings. The only time she gets a rest is after the young fledge as early as 8 days old if they are disturbed but up to 14 days in cool weather, although on average they fledge at 9 to 12 days of age. The male then pitches in to help feed the fledglings and completely takes over after a few days. In the meantime, she is busy constructing a new nest, laying and incubating the second batch of eggs.

Our overgrown, brushy, 37-acre First Field and smaller Far Field appear to be ideal indigo bunting habitats, and occasionally I discover a nest. Last July 7, while walking around the Far Field on Pennyroyal Trail, I startled a brown female that scolded and skittered off into the grass. I couldn’t persuade her to reappear, but almost immediately I discovered a nest containing three white eggs in a small black locust sapling.

Five days later I again took the Pennyroyal Trail and found the indigo bunting nest intact but empty as if some creature had tipped it slightly and removed the eggs. I suspected a raccoon to be the culprit especially after I learned that one was observed by researchers removing eggs from a nest without disturbing it, but other possible nest predators include red foxes, opossums, feral cats, blue jays and snakes.

Then, early in August, while picking blackberries in a patch in First Field, I heard what sounded like a rapid “tick-tick.” It turned out to be indigo bunting fledglings begging for food. I had an excellent look at one perched in the deepest part of the patch, well-protected from predators. Once I glimpsed the female trying to fly in to feed them, but she veered off when she saw me, not wanting to give away the location of her fledglings. The fledgling I saw did flutter off to another part of the patch so it was able to fly a short distance. Last January I found their intact nest 3 feet from the ground in a black birch sapling at the edge of the blackberry patch.

indigo bunting female by Henry T. McLin

indigo bunting female — photo by Henry T. McLin (licence)

Here in Pennsylvania indigo buntings breed from May 6 until September 11 and they have nests with eggs from May 24 until July 9. But sometimes they have clutches as late as August 3, so the nest I found at the Far Field was a late, unsuccessful clutch. Early in the season, indigo bunting nests can be heavily parasitized by brown-headed cowbirds, however, in a Michigan study, 69% of nests were successful.

Because they are generalists that adapt to a wide variety of habitats, especially interspersed woodlands and farmlands, they are one of Pennsylvania’s most common songbirds with the highest numbers in our Ridge and Valley Province. They were abundant during both atlasing projects, and male numbers are estimated at 1.5 million. Still, the Breeding Bird Survey recorded a modest 15% decrease, perhaps because of conditions on their wintering grounds.

They begin leaving Pennsylvania late in August, but peak migration occurs during the last two weeks in September. During the second and third weeks in October, 50 or more birds have been observed in overgrown, brushy fields. They spend their winters in southern Florida, Mexico, Central America, and on Caribbean islands.

indigo bunting in the rain

indigo bunting in the rain — photo by Dave Bonta

But how do they find their way? It turns out that as young birds they are stargazers. And it was Cornell Lab ornithologist Stephen T. Emlen who proved this. Using what later was called an “Emlen funnel,” he put an indigo bunting experiencing migratory restlessness or zugenruhe into a funnel-shaped cage that he had line with paper, and supplied with an ink pad perch at its bottom. The bird repeatedly leaped from the ink pad to the funnel’s side, leaving its footprints on the papered wall. In that way, the bird left a record of its migratory direction and depending on its hormonal condition, oriented north or south. Emlen followed this by proving that those songbirds that travel at night use the stars as a guide, specifically the North Star, Polaris, which stays in the same position all night and the Big Dipper and other nearby stars which rotate around Polaris in a counterclockwise direction. In addition, Emlen found that they learned their way as young birds watching the sky at night. Since his work, other discoveries about bird migration continue to be made and they appear to use magnetic fields to orient themselves too.

Indigo buntings breed from the Great Plains eastward to the Atlantic seaboard and from southern Canada to the southern United States. Then they head to their winter homes. Many indigo buntings return to the same site both in their wintering grounds and their breeding grounds, according to a variety of studies, although the males seem to be more faithful to their home grounds than females are. It’s intriguing to realize that those males I see every year sitting on the same singing perches may be as wedded to our habitat as I am.

Winter Porkies

porcupine up a tree in a snowstorm

Porcupine in a snowstorm, below the Road to the Far Field

Deep winter and at last a good tracking snow had fallen. While I may puzzle over some tracks, there is no mistaking those of porcupines. They plow through the snow on their naked, flat, pigeon-toed feet like miniature bulldozers, and when the tracks freeze, deer, opossums and foxes use them as winter highways.

When we first moved to our central Pennsylvania mountaintop in 1971, seeing a porcupine was a rare occurrence, but over the last couple decades porcupine numbers on our square mile of property have proliferated. During several days in early January last winter I found abundant tracks and numerous porcupines along the trails and in a variety of trees. Tracks wandered into and out of our three-acre deer exclosure, in and around our Norway spruce grove, and along the Far Field Road. Porcupines sat high in trees beside our hollow road, on top of Sapsucker Ridge, down in Roseberry Hollow and near the top of a Norway spruce tree. The latter was snoozing as its quills whitened in the falling snow.

Without leaves on the trees I could see many debarked crown branches. On Dogwood Knoll I found tiny pieces of bark at the base of a large chestnut oak tree, a sign that a porcupine had been eating the inner bark of one of the favorite trees of some of our porcupines. They also like red oak and sugar maple. Because they prefer small branches near the tops of these trees, we rarely lose a hardwood tree to their winter gnawing.

A tree de-barked by a porcupine near the spruce grove

A tree de-barked by a porcupine near the spruce grove

But our Norway spruce grove is porcupine central in the winter. Like white spruce further north, Norway spruce is a favorite winter food for porcupines. In addition, it provides excellent protection from winter weather. Porcupines like hemlocks too, especially for protection, and they eat the needles and twigs but not the bark because it is too strong in tannins. Our hollow hemlocks used to be popular with porcupines in the deep winter, but as the hemlocks have thinned and, in some cases, died from the ravages of the hemlock wooly adelgids, porcupines, ever adaptable, have switched to other trees, most notably our Norway spruces.

Porcupine tracks led into the grove from Sapsucker Ridge and the Far Field Road. By late January numerous spruce trees bore fresh tooth marks from gnawing porcupines. Porcupines move slowly in the woods, just as I do, so they are easy for me to track. Unlike colder, northern places, where they are out mostly at night, here they are out and about both night and day. No doubt our porcupines were especially hungry last winter because the acorns, one of their favorite autumn foods, had failed for three years.

One day I surprised a porcupine sitting on the snow-covered Far Field Road. When I approached it, it stood up and slowly climbed a large sugar maple tree. Fifteen days later, in early February, I followed what may have been the same porcupine from the base of the spruce grove to the Far Field Road. The trail ended at the entrance to a hollow, fallen log below the road where a porcupine turned its back to me.

According to Uldis Roze, who has spent 24 years studying porcupines in the Catskill Mountains of New York state, porcupine fur has excellent insulating properties, which allows them to use hollow logs, trees, and rock crevices as winter dens. Usually they turn their backs to the den openings, sit with their bodies propped up by their tails, and hold their front paws against their chests. They turn their hind paws sideways so their naked foot pads don’t touch the ground. When resting in high trees, they roll up into balls and can withstand extremely cold temperatures. No wonder they are able to live as far north as northern Alaska, Quebec, and Labrador, in fact, at or beyond the tundra line.

A young porcupine in deep snow by Martin Male

A young porcupine in deep snow (photo by Martin Male, CC licence)

By mid-February, the so-called “polar vortex” was not only dropping our thermometer to as low as ten degrees below zero on some days, but it began to snow in earnest. And again I found the same porcupine tucked into the hollow log along the Far Field Road, its back white with snow.

With 18 inches of snow on the ground, I broke out my snowshoes and headed up to the spruce grove. As I broke trail around the grove, I saw fresh porcupine tracks and then spotted a porcupine at the base of a spruce tree. It started up the tree when it realized I had seen it, but it didn’t climb more than a few feet before it went around to the back of the trunk as if once out of sight, I would forget it was there. Then I noticed a circle from its body at the base of the tree as well as a pile of cylindrical, gray and/or brown, inch to an inch-and-a-half-long porcupine scat (droppings). It must have been there for some time.

I also broke trail along the Far Field Road and encountered the porcupine in the same hollow log after a night of stripping bark from the lower spruce grove trees, just as the one I saw earlier specialized in the upper part of the grove.

Every time I passed the Far Field Road hollow log for most of February, the porcupine was either in the log or plodding its way back to it. And then tragedy struck. On February 27 I found a dead porcupine behind the spruce grove, still clinging to the thin branch of a black locust tree. Apparently, it had fallen from the large spruce it was gnawing and had broken the locust branch off on its way to the ground. Probably it had died sometime after it had hit the icy snow since there were puddles of urine around it.

Remains of the dead porcupine in the spruce grove, 7 months later

Remains of the dead porcupine in the spruce grove, seven months later

Roze says, in his book The North American Porcupine, that porcupines risk injury and death from falling out of trees because they are relatively heavy and prefer to feed far out on branches that are often brittle. I know I’ve watched them foraging on hardwood tree branches, expecting them to fall any moment as they crawl farther and farther out on a limb that bends with their weight. Sometimes porcupines do fall, but they are usually badly hurt. For instance, one of Roze’s study animals had a series of injuries that he called “consistent with falling belly-first out of a tree.”

According to Roze, another researcher, Wendell Dodge in western Massachusetts, who autopsied 200 porcupines back in 1961, found healed leg, hip, and rib fractures, broken teeth, injured eyes and ears, hernias, and soft-tissue injuries. One even had a four-inch-long pine branch in its abdomen.

A week later, in early March, I checked on the dead porcupine and found a live one sitting next to it on the ground under the large spruce tree almost as if it was holding a late wake for it. Eventually it shuffled over to the spruce trunk, deftly climbed its mostly bark-stripped trunk, and moved far out on the limb.

I followed other porcupine tracks from the upper section of the grove over to the neighbor’s clearcut on Sapsucker Ridge. There I saw a small but old chestnut oak and a bent, larger one, both of which had debarked branches. Beneath them were bark pieces and scat littering the ground. I continued following the tracks for 20 feet to the remains of a hollow tree log left by the loggers. At its entrance was a huge pile of porcupine scat. I knelt down on the snow and peered inside the log. A porcupine was tucked into it.

Both log dens were 200 feet or so from the spruce grove. While porcupines wander much greater distances during the summer, their temporary winter dens, which they use for an average of 23 days, are usually within 300 feet of their food trees. The spruce grove porcupines followed that pattern.

A porcupine in one of the hemlock trees down in the hollow

A porcupine in one of the hemlock trees down in the hollow

The same porcupine appeared three days later at the base of the large spruce where the other porcupine had died and reluctantly climbed the tree when I spoke to it. It looked as if that beautiful tree had been completely girdled high up. So too had at least four other large spruces. But according to Gary Gillmore, a state forester, Norway spruces throw out new limbs if they have been topped.

By March 10 I was seeing as many as four porcupines feeding in our hollow hemlock trees, leaving nipped twigs and scat on our road. Although this was still winter food, probably they had left dens upslope early and were using hemlock habitat for shelter, meager though it was.

Near the end of March, I found only two porcupines in hardwood trees and they were eating buds. The rest seemed to have disappeared once spring arrived. But I had enjoyed my porcupine winter and the chance to learn a little about how they survive the cold months.


All photos taken on the mountain by Dave Bonta, except where indicated.