You might guess that these clones would be identical, but they’re not. They change in appearance over the course of a year, and scientists are unsure why.
 
What do daphnia look like?
 
Examined under a microscope, daphnia in a side view usually appears almost oval, with a rounded domed head and a short spine. Seen head-on, it appears thin from side to side. Its flattened, disk-like shape offers a large surface area compared to body mass, and this allows it to remain suspended almost effortlessly in water. Daphnia has a nickname, water flea, and it’s because, like a flea, it swims in jerky bursts, using oar-like antennae.
Daphnia undergo shape changes that correspond with the seasons. While the rear spine’s length varies in successive generations, it’s the head that changes most in cyclical fashion throughout the year. Fully developed, the head resembles an absurd, high-pointed helmet. Helmeted daphnia with their greater surface area are common in summer, while helmet-less round-headed daphnia are the rule in winter.
 
As a result of these seasonal differences, early 20th-century biologists who studied plankton thought generational changes in daphnia’s surface area related directly to—or were triggered by—differing water densities.
 
Here’s how their thinking went:
Environmental temperature determines to what extent water molecules carom off one another: The warmer it gets, the more they speed up. The increased volume caused by warm water’s excited molecules offers less support to a floating object than winter’s dense, cold water. So an enlarged body surface is especially helpful when water is the least dense. This means daphnia’s increased surface area in summer helps it maintain its position in a pond or lake. But winter generations, supported by cold water’s increased density, economize by not building enlarged body parts.
But are daphnia shape changes really affected by water density changes? Such a theory of cause and effect lasted through my undergraduate days and decades beyond, but questions eventually arose, and so many other explanations became plausible that water density could no longer be considered a primary cause—if it were a cause at all.
Science is self-correcting. When a theory doesn’t stand up under scrutiny or the test of time, it is replaced by another (or others!) closer to a solution.
   
Have scientists settled on an answer? Do we know why daphnia change shape?
 
Many theories now exist. Heated arguments can develop in the world of science and, odd as it may seem, some of them revolve around the cause of daphnia’s changing helmet size.
   
One theory is that daphnia’s enlarged shape in summer makes it tougher to be gulped down by its small predators, whose numbers are also up during the warm season. Other theories suggest that shape relates to the need for altered swimming behavior or to the abundance or absence of certain food.
 
Whatever the cause for change, it must be important. Daphnia’s different generations would not be expending the energy and materials necessary for summertime bodybuilding without some kind of environmental or physiological pressure.
   
It remains possible that none of the theories in vogue hold water, or that several factors interact with one another to cause the change.
 
No one can claim the workings of nature are simple. Daphnia’s unexplained change from winter to summer is proof.

The class, tree-huggers by and large, many hailing from non-New England states, sat as if struck by a falling limb. Only those sitting in the front row, or those with a taste for this sort of thing, noticed the twinkle in the professor’s eye.

He was right, of course, ecologically speaking. We live in the woods here in northern New England; forests are the defining feature of our ecological niche. If we halted our clearing and haying, paving and grading, logging and lawn mowing, the woods would swallow us whole within a century.

In fact, over the past century, they nearly did. Vermont was three-quarters deforested in the middle 1800s; now it’s three quarters the other way. According the most recent U.S. Forest Service data, Maine is the most heavily forested state in the nation, with nearly 90 percent of its acres in woodland, followed closely by New Hampshire at 84 percent.  Vermont picks up the bronze with 78 percent, though New York would certainly be on the podium if only the Adirondacks region of the state were counted.  We live in the woods.

That’s true in another way as well: Vermont is the most rural state in the nation, with 62 percent of the population living outside of urban centers (as defined by the U.S. Census Bureau) Maine is second with 60 percent. New Hampshire is well down the list at 41 percent, but if you stripped off the seacoast, it would certainly rise to the top tier of rural performers.

Many of us are surprised to learn that our states are so rural; places like Alaska or Wyoming typically come first to mind. But here’s the crucial distinction: rural means that people live in small towns, not that a state is sparsely populated. Wyoming is actually a relatively urbanized state, with only 35 percent of its population living in small towns—even while it is also among the most sparsely populated. Rural means a village green, a church with steeple, a post office, a store with a few gas pumps, in short, communities where everybody knows everybody else.

And in New England rural means people living in the woods. Not nearby the woods or within an hour’s drive of the woods, but in the actual woods. It’s easy to forget that no other part of the country is quite like this.

We also forget because, for most of us most of the time, we spend our days in the cleared areas: among the buildings, roads, lawns, and pastures where we live much of our lives. The woods can fade into the background, except perhaps during autumn foliage season, and recede from our consciousness. We’re like kids who, having grown up in inland towns without ever having set eyes on the ocean, can be forgiven for still believing, at some level, that most of the world must be dry land.

Back on our farm, a half-century of mechanical haying has allowed saplings and small trees to slowly creep in from the old stone walls, gradually extending the forest’s hold. Few farmers want to snag a sickle bar or cutting head on a sapling or stump, so year by year, as the seedlings creep in, the hay-able field is reduced. An occasional intervention is required if you want to reverse this process, and this winter, with very little snow falling in the lower reaches of the Connecticut Valley, has been perfect.

I’ve been able to cut the larger trees and saplings right at ground level, preparing the ground for brush hogging in the spring. I figure I’ll be able to push the woods back by an average of 20 feet over a 1,000-foot treeline, which will amount to just under a half acre of new field and pasture. Very satisfying work.

You might think, after all this, that I’m anti-woods. Not at all; I spend as much time in the woods as I can. It’s just that our farm is 78 percent wooded, and I’m mindful of my former professor’s advice that eternal vigilance is the price of pasture.

But late one afternoon last month, we arrived home to find that our rooster was missing. Our half-dozen hens, a mixed bunch of Rhode Island Reds and Wyandottes, were cowering in the small space beneath the chicken house. We found the partly eaten rooster carcass still in the pen, under an inch or two of fresh snow that had obliterated any tracks or signs of a struggle. I removed the dead bird and retired for the night, wondering what predator had struck.

Morning revealed the culprit. Sitting on a low stump inside the pen and eyeing the chicken house was a large hawk. Its tracks in the snow showed where it had landed in search of the rooster leftovers that it evidently had planned for breakfast. I grabbed my camera and snapped its ‘mug shot,’ capturing its prominent white ‘eyebrows,’ dark cap, and body coloration that perfectly matched a photograph in the bird guide. The suspect was a northern goshawk, a big bird, about the size of a red-tailed hawk, with dark gray plumage and an off-white breast. When it flew off, it flashed the characteristically bright white plumage beneath its tail.

This raptor is an uncommon, if not rare, species across the northern United States. It favors northern boreal forests in the eastern part of its range and has a year-round presence in Vermont and New Hampshire. It is the largest and, by all accounts, most aggressive hunter in the group of hawks known as accipiters. These hawks do not soar and then plunge from above; they are adapted to hunt in forests, where they move stealthily from perch to perch, stalking prey among the trees and brush. When they spot something, they attack swiftly, almost horizontally.

Goshawks are equipped with wide, powerful wings and long tails for sharp maneuvering through the woods. Their acceleration from a standing start is stunning. Bold and persistent, they dive into thick brush in pursuit of squirrels, snowshoe hares, ruffed grouse, crows, woodpeckers, and large songbirds, such as the American robin. And of course, chickens. Goshawks have been known to barrel into barns after chickens or snatch them at the very feet of their keepers.

Apart from these incidents, goshawks are seldom seen or heard. They are most likely to reveal themselves in breeding season, when both males and females give calls that sound somewhat like the noises made by seagulls. In New England they nest in the interiors of extensive, mature forests on moderate slopes with an open understory. They prefer sites near water, and they usually give human presence a wide berth. The goshawk’s hallmark ferocity extends to protection of its nest, so it will attempt to drive off intruders, including people, with talon-wielding charges.

The goshawk does have a long association with humans, who centuries ago found ways to exploit this hawk’s hunting prowess. As early as the third century A.D., goshawks were tamed and used in the sport of falconry in China and Japan. In the West, goshawks were used in falconry by mid-eastern and Germanic tribes; the goshawk was so revered, in fact, that Attila the Hun adorned his helmet with the bird’s image. Later, in medieval Europe, the goshawk was prized as ‘the cooks’ hawk,’ a reliable provider of meat for the table. But with the introduction of firearms and the decline of falconry, goshawks eventually became targeted as poultry thieves. In the United States, goshawks and other raptors finally gained federal protection in 1972, so it is now illegal to possess or kill them.

The goshawk that claimed our rooster has not returned, thankfully. Perhaps it was a migrant moving southward just as we were moving deeper into winter. We missed our rooster, but where we live, I accept predation as part of the natural order. At least our rooster was taken not by some common predator but by this formidable king of the forest.

If I could stir myself sufficiently, I’d approach the brook’s icy edge to see what’s happening. For the best viewing I could use the equipment of warmer months, but right now submerging my face with a mask and snorkel is unthinkable.

A simpler and more comfortable option might be to cut a small window in the ice through which a surprising amount of life activity can be seen even without a mask. Or seek an already ice-free patch.

What is there to see in an icy brook?         

Insects for one thing. Even if there are fewer varieties to see in winter, the populations of particular species can be enormous. Grab a quick handful of leafy waterweed (Elodea) or gritty stonewort (Chara) growing on the bottom, swish it in a bowl of tap water, and hundreds of backswimmers and mayfly nymphs will be evicted from their winter refuge.

Depending upon the species, the insects in a winter stream exist as adults, nymphs or larvae—often changing location in the water to avoid detached or shifting ice. A few species, like mountain midges, get through the winter as eggs; others, like crawling water beetles, freeze in ice, only to re-emerge unscathed in spring. To escape crushing ice or late-winter floodwater, mobile insects tend to seek protection in crevices or pools to the side of the stream. They return to their usual habitats when conditions improve.

Active insects must adjust their diet in winter. Instead of browsing on summertime’s sun-loving filamentous green algae, mayfly nymphs in winter turn to scraping algae off rocks, especially single-celled green desmids and a golden-brown algae known as diatoms.

Predatory dragonfly and damselfly nymphs as well as powerful dobsonfly larvae (called hellgrammites) retreat to sheltered spots in crevices, under rocks, or in the quieter waters of sand-strewn eddies. Feeding opportunities are lessened, but these fierce predators remain ready for whatever comes along.

In winter – as in summer—caddisfly larvae hang out in the quieter spots in the stream, providing them security, while their perfectly formed nets, made of silk emitted from salivary glands, catch anything, living or dead, coming downstream. As winter progresses less food is available to be caught in nets, so the larvae turn to suspended diatoms and desmids rasped off rocks by upstream ice. By late winter their nets, worn and torn, finally come apart, and the larvae hunker down and begin their slow metamorphosis into summer’s adult form.

Another brook insect larva, that of the notorious black fly, lives near riffles in the swiftest flow. It unfolds fringed antennae that catch whatever tidbits of plant and animal material come along. If a larva is dislodged from its holding, it returns to its original site by reeling in a silken lifeline.

Like other brook insects passing through complete metamorphosis, a black fly’s pupa remains underwater. Over time, it shortens and thickens to become a streamlined humpbacked knob cemented to its parent rock. Its antennae extend into the current to also provide the oxygen necessary for the insect’s transformation into an adult.

In spring an adult black fly emerges from its underwater pupa and is whirled to the surface in a bubble of air. Soon afterwards, it breaks free and becomes airborne —heading off to seek that tender spot behind your ears.

While there is a surprising constancy in a brook’s insect population throughout the year, winter’s inhospitable conditions help dictate a particular insect species’ stage of growth and how and when it ends an aquatic existence to begin a terrestrial life.

Adaptations for survival in cold, turbulent, highly oxygenated water are so pronounced that if a brook insect is removed and placed in a still aquarium, it will quickly show signs of distress. Even if the aquarium water is well aerated, the water’s oxygen content is a far cry from that of a brook in February. The insects will try to cope but almost always succumb.

I’ve built a couple of big complicated Plexiglas affairs that simulate natural conditions well enough for some mountain brook creatures to live fairly normal lives. It’s not easy, nor always successful, but it does offer a view of their otherwise hidden world. It beats sticking your head through a hole in the ice.

The usual suspects arrive – chickadees, blue jays, downy and hairy woodpeckers, nuthatches and goldfinches – but each winter also brings some birds down from the arctic, such as pine siskins and redpolls. From the south have come cardinals, tufted titmice, and, last year, a red-bellied woodpecker. The once-abundant evening grosbeaks have not been here in years. Occasionally a hawk zooms in, attracted to what we’re attracting.

We feed the birds because, of course, we love the activity and splashes of color they bring during this spartan time of year. My wife records in her watercolor journal what we see, and I usually watch the goings-on from a comfortable observation post, the sofa.

In the past 20 years or so, bird feeding has grown enormously. Millions of Americans now engage in it, making it almost as popular as gardening as a backyard activity. A $3-billion industry has grown around it – from farms producing seed to companies making and selling feeding equipment. A million tons of seed and grain are sold each year in this country for feeding wildlife – mostly birds.

No question birds delight both young and old. Many birders say their interest in birds began by looking out the window. Thanks to observations of activity in backyard feeders over the years, a large database of information is growing, helping ornithologists study species decline and geographical range shifts.

This is all to the good, but as I feed the birds I also wonder whether I’m doing a good thing. Am I a kind of zookeeper, who is turning wild birds into pets, undermining their ability to survive on their own? By encouraging unnatural concentrations of them for our viewing pleasure, are we skewing more normal relationships, even allowing some species to survive where they otherwise wouldn’t? Are we helping to spread bird diseases?

I’m not alone in my questioning. Some research scientists and conservationists think feeding is harmful to birds in a variety of ways. (An article titled, “Crying Fowl: American Backyard Feeders May Do Harm to Wild Birds,” appeared in “The Wall Street Journal,” Dec. 27, 2002). Others, however, including John Fitzpatrick, director of the renowned Cornell Lab of Ornithology, strongly feel just the opposite. He believes that the data indicate feeding is largely beneficial (“In Defense of Bird Feeding” in “Birdscope,” Vol. 17, # 2, 2003).

The debate over the affect on birds notwithstanding, I have other concerns. As great mounds of discarded seed husks emerge around our yard at the end of winter, I wonder how many acres of monoculture it takes to produce all this. Did the acres of cultivated fields replace a more natural environment? How much pesticide was used to produce the seeds we lug home in 50-pound bags?

I see other drawbacks. Wild mice and red squirrels, sustained by pilfered feeder seeds, share our house with us. Each year I fill holes that woodpeckers have drilled into our wood siding. I shoo away cats staking out the feeder or shrubs. Deer by the droves come at night for seeds on the ground, and wild turkeys, 30 at a time, churn up our lawn.

With an increase in year-round feeding across the region, black bears in summer have learned about the treasure-troves in feeders and garbage pails on porches. This has lead to many human-bear encounters and the occasionally killing of a marauding bear.

And all too frequently, my wife and I hear the sickening thud that tells us yet another victim has hit a window. Nationwide, several hundred million birds die each year by striking windows – mostly on skyscrapers during migration, but also on houses.

I even worry about my viewing from the sofa. Am I may becoming a tad more complacent about getting outside? Perhaps this preoccupation with bird-feeding is just another mindless substitute for a television program.

But even if I wanted to stop, I don’t think the birds would let me. If I’m outside and forget to load the feeders, the chickadees fly at me and chatter in my face. Or if I’m inside and late to serve breakfast, they’ll bat themselves against the window. Once, as I was bringing in firewood, one lit on my hand; I dropped the wood and walked around the house to the feeder, and there it was … waiting for me. The woodpeckers, too, are demanding – they rat-a-tat against the house when the suet cage is empty. No, the birds wouldn’t let me stop. They have me well trained.

But the reality is, we couldn’t live without them. Bacteria and other microorganisms, like yeast, make life not only possible but also pleasurable.

In fact, the vast majority of microorganisms are helpful to humans; no food of any kind could grow without them. Only a small number are the disease-carrying villains that we automatically think of when we hear the word “bacteria.”

Think of some of life’s great gustatory pleasures – a loaf of fresh bread, a glass of wine or beer, a slab of cheese, all deliberately created with the collaboration of certain microorganisms. And since a good deal of our local economy depends upon the production of dairy products, like cheese and yogurt, we should consider ourselves as having a vested interest in the well-being of our tiny bacterial allies.

To begin with, no animal, ourselves included, could digest its food without bacteria – specifically, the trillions of one-celled organisms that live within the gut of every creature that walks, swims, splashes or flies. Special bacteria living in the multiple stomachs of cattle allow them to break down cellulose and thereby digest grass. Hence, we owe our glass of milk to the presence of bacteria as well as the presence of cows.

Roughly one-third of the total number of bacteria in the human system are members of the bacteroides group, which produce enzymes that digest the cell walls of vegetables, allowing us to absorb the vegetable’s nutritional elements. Other bacteria in our bodies produce important vitamins, and certain bacteria even prevent the growth of other bacteria that could make us sick.

Some bacteria, of course, can have unpleasant and even life-ending consequences for us. They cause odor. Bacteria on tongue, teeth, and gums give off waste that causes bad breath. Our bodies eventually become covered with skin-borne and airborne bacteria that die and become smelly. By the time we towel ourselves dry after a shower, new microbes already have begun setting up shop.

In our kitchen, we must guard against food poisoning from salmonella and botulism. Airborne bacteria can cause strep infections and tuberculosis, and sexually transmitted bacteria can cause syphilis and gonorrhea. (Many diseases, from the common cold to AIDS, are caused not by bacteria but by viruses, which are altogether different. Viruses, most of which are 100 times smaller than bacteria, are not organisms at all but a type of genetic material that can enter our cells and kill them.)

But most bacteria and many other microorganisms help us in stunningly broad and complex ways – from enriching our garden soil with nitrogen to decomposing our waste in sewer plants.

Among the bacteria we find helpful are lactobacillae – without which we wouldn’t have much of a dairy industry. When Lactobacillus cremoris and certain molds make their way into milk, or are carefully introduced, delicious cheeses can result. Lactic acid bacteria (LAB) help make cheese by fermenting the milk’s lactose (milk sugar) into lactic acid, which assists coagulation and contributes to the flavor and consistency of the cheese. Lactobacteria also slow the spoiling of cheese and prevent the growth of pathogenic bacteria. Molds in certain cheeses are evident to the eye – they form the blue streaks we see in blue cheeses—and certainly pleasing to the taste buds. 

Yeasts, used by mankind for thousands of years, were probably the first type of microbe to be used for domestic purposes. A particular kind of yeast, Saccheromyces cerevisiae, makes bread rise by producing gases as they metabolize and reproduce. There is something highly satisfying about being in a warm kitchen on a cold day and watching a quiescent mass of water, flour, and yeast change and swell and become loaf-like. It’s food that is literally alive – until we eventually kill all the yeasts within the bread by baking it.

As yeasts metabolize, they can also convert carbohydrates into another welcome by-product: alcohol. Home brewers and the region’s micro-breweries would be at a loss without brewers’ yeast.

So, go ahead and wash your hands to protect against those dangerous “germs.” You really should. But don’t forget that it’s our tiny microbial allies that you must thank for your tasty lunch of bread, cheese, and beer.

It’s true that trees sequester carbon, a byproduct of our fossil fuel addiction and a leading cause of global warming. It’s also true that during photosynthesis, trees and other plants draw carbon dioxide from the air, mix it with water taken from air or soil, and, in the presence of sunlight, create sugars and other carbohydrates, all of which contain carbon.

If you could throw an enormous plastic bag over a tree and measure the flow of gas in and out of the bag, you undoubtedly would find that the tree was removing carbon dioxide from the atmosphere and storing it in the wood.

This simple botanical truth, however, has led to a larger fiction: that forests could sequester enough carbon to prevent further changes in our climate. They can’t.

What some policymakers suggest by promoting carbon sequestration is that if a much bigger plastic bag were placed over all the forests of the world we would find that the trees and plants were working, collectively, to scrub the atmosphere of excess carbon dioxide. Our forests can never do that; and the reason, in part, is that while some trees and plants bloom and grow, others simultaneously die and rot, releasing carbon back into the atmosphere. It’s a closed loop. 

Although there are times when certain forestlands do accumulate more carbon than they release – such as when they are fast growing on once-cutover land or when they are very old, living on thick, carbon-accumulating soils – the net global balance from wooded land over time is essentially zero.

Deforestation is another story altogether. The Intergovernmental Panel on Climate Change, established by the United Nations, has estimated that deforestation is currently responsible for 20 percent of our annual carbon dioxide emissions. When forests are turned into farm fields, housing sites and parking lots, these carbon dioxide emissions increase. So keeping existing forests intact will certainly help curb future emissions.

But even if we stopped the loss of forestland, this wouldn’t reverse the burgeoning atmospheric carbon levels. And that’s because the other 80 percent of our carbon dioxide emissions come from burning fossil fuels, such as oil, gas and coal, which are the byproducts of the decomposition of trees and other plants that grew hundreds of millions of years ago. No matter how cleverly we manage our forests, no matter how many trees we plant, we can’t compensate for the carbon dioxide and other pollutants released from these fuels. 

“But”, you might ask, “Isn’t managing our forests still important?”

Absolutely. But managing forests for maximum carbon storage also would mean not managing them – or at least not managing them as much – for other things our modern society enjoys.

Here in the Northeast, we presently manage our forests for many reasons – to use them as wilderness and aesthetic sanctuaries; to harvest them for timber, firewood and pulpwood; to use them for recreation, crisscrossing them with trails and roads; and to use them as refuges for wildlife and biodiversity.

This last point is perhaps the most critical: A full range of plants and animals requires a full range of forest types, from the very old to the very young and from the vast expanse to the tiny plot. If we settle on just one type of forest – the one that ends up storing the most carbon over the short term – we’ll be inevitably compromising on the rest.

“Plant a Tree – Save the Earth” is a catchy slogan that has validity only if you accept that your tree for a while will suck up the carbon given off when another tree is cut. It’s a feel-good exercise. You won’t be compensating for the carbon emitted as you drive to work or fly off on vacation.

This not to suggest we ignore the message of Arbor Day. Trees bring shade, quiet beauty, lumber, firewood, birds’ nests and raccoon hideouts. In the grand scheme of things, that ought to be enough.

Neither Monty nor I have good reason to feel this way. We are warm, securely housed and well fed. But many of our neighbors in the animal world fare otherwise. Insects, reptiles, amphibians and many species of small mammals require a season-long nap – hibernation – to survive.

From our glances outside today Monty and I see chickadees at the feeders, and a few red squirrels in the yard, but that’s about it. Many northern woodland creatures have tucked themselves away and disappeared now that the ground is blanketed with snow and the skeletal trees glisten with ice.

The mammals among these creatures, such as woodchucks and chipmunks, are hibernating in the secure retreats that they prepared many weeks ago, homes that are insulated to a degree but certainly not heated. Their challenge is to survive winter on the reserves of internal fat built up thanks to the rich larders of summer and fall.

Among mammals, it’s the smaller ones that are true hibernators. And size is a determining factor. With an expansive skin covering relatively small bodies, too much of their body heat would otherwise be lost by radiation into the cold air.

Hibernation allows animals to survive because in this quiescent state they have little need, if any, for high-energy food that in winter is hard to find. Traveling long distances to look for food can require expenditures of more energy than some animals have at their disposal. The search is not worth the effort.

During hibernation the heart rate slows; circulation becomes sluggish; breathing is almost imperceptible; metabolism lowers significantly; body temperature falls; muscle tone lessens, and brain function is minimized. Most hibernators don’t eat or drink anything, and excretion stops, although some small rodents awaken occasionally to dine on stored food. Hibernation is a coma-like state. Come spring, it can take a day or two for recovery.

Large mammals don’t need to hibernate. Because their surface-to-body- volume ratio is much less, they don’t lose as much heat. They also are more adept at finding food: Moose and deer, for example, can find bark, leafless shrubs, twigs, acorns and green plants beneath the snow.

One large mammal in the northern forest, the black bear, hunkers down in a den for a long winter’s slumber that some people mistakenly refer to as hibernation. But since the bear’s body temperature drops only a few degrees and its metabolism remains relatively unchanged this isn’t true hibernation. The sleep, itself, is not as deep as that of smaller creatures. A bear is apt to awaken and even briefly leave its den during a warm spell or if it is disturbed.

Hibernation is not sleep, though it resembles sleep. Some reductions in brain and body function associated with hibernation occur during an eight-hour slumber. But sleep is more a matter of altered brain activity than physiology.  Hibernation is a physiological condition controlled largely by pituitary and thyroid hormones and by insulin from the pancreas.

How do animals know when to begin hibernating? They have internal biological clocks keyed to the number of daylight hours. Changes in food supply, temperature and weather also figure in.

The process isn’t immediate. When it turns dark and cold, animals don’t just call it a season and bed down for six months. They must prepare for hibernation. In late summer and fall they improve their dens and nests, insulating them and even camouflaging them against non-hibernating predators. As food supplies dwindle in autumn, they recognize the warning sign and begin gorging themselves to increase internal fat. Some stash away as much dry imperishable food as possible in storage chambers. Chipmunks, for example, will awaken briefly in midwinter to nibble on their stores.

Once in hibernation, a mammal’s well being is controlled by an inborn “thermostat” that kicks in or out depending upon a physiological need to burn fat. This “thermostat” helps maintain the minimum temperature needed to keep metabolism ticking along at a still-reduced level.

Carnivores rarely hibernate. Even under winter conditions a carnivore almost always has some food at its disposal; it has at least some chance of killing another animal—even if it’s just a mouse well-hidden under snow. This is one reason why Monty, no matter how tired or bored, will happily sleep but never hibernate.

Well, sometimes you get what you wish for. The attic of our house is ventilated at each end by screened openings protected from the weather by wooden louvers. On one of our infrequent trips to the attic we noticed an untidy mass of leaves stuffed between the screen and the louver. As we investigated, the leaves began to stir. Out popped the most adorable little animal, with soft gray fur and enormous dark eyes. It surveyed us anxiously for a few moments, then slipped through the louver and launched into mid-air. Flattened, like a furry kite with tail outstretched, it glided in a downward arc to a nearby tree trunk and scurried from sight. Again the leaves rustled, and one by one, four nest mates emerged and repeated the graceful aerial voyage. We had not just one flying squirrel but a small colony.

While few people have seen this secretive nocturnal creature, flying squirrels are in fact common in the forested Northeast. In Vermont and New Hampshire, two species of flying squirrel overlap ranges. The northern flying squirrel, rich brown and bigger (to 14 inches long, nose to tip of tail), ranges down from Canada, while the southern flying squirrel, paler and smaller (to 10 inches long), is found just south of the Canadian border all the way to Florida. Surprisingly, the diminutive southern species is more aggressive and is known to drive off its northern relative.

A more appropriate name for his creature might be ‘gliding squirrel,’ since these animals do not truly fly. A large flap of skin, called the patagium, extends from the animal’s flanks and attaches all the way to wrist and ankle. To glide, the squirrel leaps out and spread-eagles itself, pulling the patagium taut. Buoyed on this aerofoil, it floats outward and downward, in ideal conditions sailing three feet for every one-foot drop. A squirrel launched from 100 feet up could glide the length of a football field.

The patagium is not just a passive membrane, rather it consists of various muscles, including one along its border that tightens or slackens to assist steering. A special cartilage strut hinges out from the foreleg to stiffen the patagium’s leading edge. Gliding squirrels are highly maneuverable and can weave between trees and branches. The squirrel’s tail, much like the tail of a kite, acts as a stabilizer, important for balance. On the approach to its landing on a tree trunk the squirrel draws in its forelegs, and the patagium folds to become a parachute for the touchdown, hind feet first. Upon landing, the squirrel often hurries to the opposite side of the trunk in case a predator is following. As an additional safeguard, the squirrel’s brittle tail breaks off if grabbed.

The hauntingly large eyes of flying squirrels help them to see and fly by night, which means they don’t have to worry about daytime predators. Their eyes are on the sides of the head, producing a wide visual field for predator spotting, but not much three-dimensional vision, as this requires forward-facing eyes with visual field overlap. Thus, before gliding on a new route the squirrel bobs its head about, taking several different views to gauge the distance to the landing spot by triangulation. Once a route is learned however, they no longer triangulate. In fact they barely look. Squirrels have been known to crash-land repeatedly when a tree on which they had habitually landed has been cut down.

Gliding in the dark can be hazardous, so flying squirrels sport the longest whiskers of any squirrel to help detect twigs and other obstacles. Additional whiskers around the eyes may function to warn of an impending poke in the eye.  The squirrels also protect their eyes by momentarily shutting them while they land, a behavior revealed through examination of video footage.

If you live around large areas of mixed woods with mature oaks, beeches and large dead trees, you could be amongst flying squirrels. These animals subsist primarily on nuts and acorns, but they also consume fruit, berries, fungi, plant buds and flowers. Despite their cuddly appearance, southern flying squirrels have the dubious honor of being the most carnivorous of our squirrel species. They spice up their vegetarian diet with bird eggs and nestlings, carrion, shrews and mice (as do all squirrels but in smaller amounts.)

Flying squirrels like to live in the cavities in dead trees, in woodpecker holes or in the cozy space of someone’s attic. Tracks on the snowy roof beneath our attic louver remind me that these creatures don’t hibernate and will be out gliding whenever winter nights are mild.

Overwintering species have various tricks for survival. The downy woodpecker excavates cavities in trees for shelter. Black-capped chickadees lower their nighttime body temperature to save energy.  American goldfinches, which have about 1,000 feathers during the breeding season, molt in late summer and grow about 2,000 new ones for winter insulation.

When it comes to winter adaptations, however, it’s tough to beat the ruffed grouse. It has all kinds of adaptations, including the ability to hide out under deep snow. 

A ruffed grouse, which is about the size of a small chicken, is well camouflaged with mottled brown feathers that blend with the forest floor during spring, summer and fall. In these seasons they spend much of their time eating more than 100 kinds of plants, mostly leafy ground vegetation. In winter, however, with most of these food sources buried by snow, the ruffed grouse changes its diet, moving to buds, twigs and catkins.

By far the most sought-after winter foods for grouse are the sugar and protein-rich flower buds of trembling aspen. Grouse also consume the buds and catkins of big-toothed aspens, birches, alder, willow, beaked hazelnut and ironwood.  To digest woody material, they rely on a gizzard, a part of their digestive tract, where with the help of tiny pebbles that they swallowed, they are able to break down the tough cellulose fibers.

Ruffed grouse are poor at storing fat. That means they must eat large amounts of food daily, usually at dawn and dusk. But they must be careful to avoid lingering while feeding, as they’re exposed to predators while feeding on the buds of leafless trees. Red-tailed hawks, goshawks and great-horned owls are quick to spot them.

The ruffed grouse does have a way of minimizing risk while dining.  They eat fast. In 20 minutes a grouse can swallow enough buds to make it through the day.  It is able to do this thanks to its crop, a wide portion of the esophagus, which acts as a storage chamber for consumed food. With a loaded crop, the grouse flies to a protected area, where it can safely digest its meal.

Ruffed grouse have other physical and behavioral characteristics that help in winter. In September, fleshy projections – pectinations—begin growing on the sides of their toes.  These comb-like nubs, which fall off in spring, increase the surface area of the foot. Working like snowshoes, they allow the bird to walk across snow with less effort.  Pectinations also give the grouse a better grip on an icy branch where it might perch while feeding.

A grouse, in cold weather, develops special feathers that extend down its beak, covering its nostrils, allowing the bird to breathe in warmer air.  Ruffed grouse also have feathers partially covering and insulating their legs.

The ruffed grouse is famous for its winter roosting routine, commonly referred to as “snow roosting.”  With no snow, or just a few inches of it, the bird is likely to seek protection in conifer stands. If the snow is soft and a foot or more deep, however, the grouse is likely to spend the night in an insulated, air-filled snow tunnel. The grouse builds this tunnel by first plunging from a tree into the snow. Then with its wings and feet the grouse extends the tunnel, sometimes to as much as 10 feet. Recent research suggests that the temperature in a snow hideaway may warm to 32 degrees Fahrenheit and that it rarely falls below 20 degrees—even when it is much colder outside. This tunnel helps the grouse conserve energy, so it needs less food. Less time spent in the open also means less time being exposed to predators. 

A ruffed grouse exits its tunnel with a flap of wings and burst of snow that will scare the daylights out of any snowshoer or skier happening by.  When in the woods, be prepared for such a surprise, while also looking for wing impressions in the snow, sure signs of a quick departure for a quick breakfast.