Thursday, April 18, 2024

Appreciating Earthly Gifts

What if we stopped calling trees, water, minerals, fruits, fish, soil, and everything else Natural Resources and started using the term Earthly Gifts?

This was one of the first questions posed by Dr. Robin Wall Kimmerer at a talk last month in La Crosse, WI. Kimmerer is the author of Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teachings of Plants. Published in 2013 without much fanfare, this amazing book slowly gained momentum by word of mouth, and finally reached the bestseller list in 2020. “I’d like to be named Head of the Department of Earthly Gifts,” she quipped, not truly joking.

As spring turned to winter and back to mud season in the days since that talk, I’ve been thinking about Robin’s words…and finding her ideas echoed elsewhere. Kathleen Dean Moore is another of my favorite authors, who, like Kimmerer, won the Sigurd Olson Nature Writing Award. I’m often delighted by how Moore and Kimmerer arrive at the same conclusions from their different backgrounds—Moore is a Western philosopher, and Kimmerer gains wisdom from her Indigenous heritage.

They both encourage us to appreciate gifts from the Earth.

Moore wrote, “The Earth offers gift after gift—life and the living of it, light and the return of it, the growing things, the roaring things, fire and nightmares, falling water and the wisdom of friends, forgiveness…Failing to notice a gift dishonors it, and deflects the love of the giver…But to turn the gift in your hands, to say, this is wonderful and beautiful, this is a great gift—this honors the gift and the giver of it…”

Here are a few of the Earthly Gifts I’ve received recently. Please admire them with me, and then reflect on a few of your own.

1. Voices and laughter echo throughout the Museum even though we’re closed. Hammers pound, drills squeal, paintbrushes swish. We’ve asked our volunteers to do the oddest things: install a giant slide indoors; adhere a big sticker printed with the face of a marten to our doors; line the entire exhibit hall with fabric printed to look like the inside of a snowbank; enlarge animal tracks to 12x life size and then glue them to strips of chiffon and hang them from the ceiling; write flute arias to represent ten beings who live beneath the snow, and so much more. The list of volunteers grows longer every day, and the table can barely accommodate us all at lunch. As it turns out, it takes a village to turn an exhibit hall into the Subnivean Zone at 12x life size. “Anaamaagon: Under the Snow” opens in May, thanks to the work of many talented volunteers, Museum staff, and professional artists!

Volunteers work in the exhibit hall. 

2. On a rare day away from the commotion, my friend and I hike through birch woods below a craggy, mossy cliff. The sound of a hundred little bells makes us look up from the rocky path, and we discover that the trees are twinkling with the movement of birds. As we walk, a huge flock of redpolls tumbles ahead of us. They hop and poke about the leaf litter looking for seeds as their friends fly just ahead; then when the back of the flock reaches the ground birds, they flutter up. The beings ahead of them flutter up. The beings ahead of those flutter up. The movement is delicate and overwhelming. My heart flutters up, too. We shake our heads in wonder.

Can you spot the redpolls?

3. Most plants—at least the smart ones—are still holding their buds tightly closed against the possibility of frost. But I know to look more closely. Leaning into a certain shrub, I carefully examine the tip of each brown bud. It only takes a few tries before I find what I’m looking for: tiny, translucent, red tentacles squeeze their way out of the bud scales. Shifting around, I position the Sun just so, and the pistils of a beaked hazel flower begin to shine as if from within. As if they are the light inside a film projector, memories begin to play: spring in California and the comfort at finding an old friend in a new place; the pandemic spring when I walked down my road every day for two weeks straight, waiting for them to emerge from their homes, too; and countless other tiny scavenger hunts when I looked for these tiny flowers and found joy.

The translucent red pistils of beaked hazel never fail to bring me joy in the spring.
Photo by Emily Stone.

4. Awake in the darkness, I stress about falling back to sleep. Then the loons begin. Soft wails echo across the lake and seep in through my windows. These are the first I’ve heard this spring. Now I’m grateful I didn’t snore right through them.

Loons from last summer.

5. On a walk, the rattling bugle of a sandhill crane raises the hairs on my neck. I follow the sound across a field, between trees, and onto the edge of a bog. Through a screen of alder twigs I watch a single bird. Neck stretching, wings flapping, they call again and again. Then, with a few running hops they are airborne on wings so large I can feel the breeze they stir in my soul.

The rattling bugle of sandhill cranes always makes me pause and be grateful for the wildness of the world where we live. Photo by Emily Stone (in Nebraska, not Wisconsin).

“We are called to live lives of gratitude, joy, and caring, profoundly moved by the bare fact that we live in the time of the singing of birds.” – Kathleen Dean Moore, Wild Comfort

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, April 11, 2024

Finding Snow Fleas

With soggy skies above and soggy snow below, my recent hike on the North Country Trail was not inspiring a love for spring. But with my head bent to watch my footing, I noticed a sprinkling of debris coated the surface of the softening snow. Suddenly one of the little specks vanished. Crouching down for a better look, I discovered that most of the sprinkles were tiny, leaping springtails known as snow fleas. I dug out my macro camera.

While springtails have six legs, they aren’t insects. Instead, they belong to the insects’ sister group with several different characteristics. A lack of wings, simple instead of compound eyes, differences in molting, a special mouthpart for drinking, and a hinged body part that can fling them into the air set springtails apart from true insects.

A springtail’s namesake spring is a forked appendage called a furcula, made from two modified legs on their final body segment. In my research, I found photos of two-pronged furculae, but in the photos and videos I captured of these little beings, the furcula has three prongs (see above photo).

While resting, a springtail locks the prongs of their furcula up against their belly, thereby storing potential kinetic energy in their abdominal muscles. A rubber-like protein called resilin in the springtail’s exoskeleton helps to flex and store energy, too. The whole system is similar to an upside-down mouse trap.

When the springtail is startled by a potential predator, such as a giant human hiker, they release the clasp and the furcula snaps open against the ground. The being launches into the air, as far as 100 times their one-eighth-inch body length! This explanation, summarized from a variety of sources, makes me think that it would be impossible to see the furcula before the springtail goes flying. However, my videos show the furcula expanding from the springtail’s rear end for a second before they disappear. 

After an uncontrolled flight, a springtail might land mere inches from their starting point, which is still far enough to fool many of their predators—like ants, beetles, and salamanders. Post fling, springtails don’t always land on their feet. Luckily, they have a neat trick for righting themselves. Two inflatable grooming tools not only help them to keep clean, the sticky tubes can be adhered to the ground and used to pull the springtail upright.

While springtails are in the running to be the most abundant of all macroscopic animals (you might find 100,000 individuals in a square meter of soil, and there are about 3,600 species total), we typically only notice the one or two species who spend time on the surface of snow. Snow fleas get their name from their jumpy behavior and the substrate that makes them visible.

On balmy winter days, snow fleas scatter like pepper over the surface of the snowpack, or they might congregate in crawling hordes of a million individuals, drawn together by pheromones for a mating party. It’s amazing that such a tiny being can survive at all in the frozen expanse of snow. The magic that makes this possible is a unique protein especially rich in the amino acid glycine. This protein binds to ice crystals as they start to form, preventing them from growing larger, and so it acts as an antifreeze. The protein works down to about 21°F, and at warmer temperatures it disappears! Doctors are studying its potential to help preserve human organs on their way to a transplant surgery.

Snow fleas don’t really spend much of their life on top of the snow. Like other springtails, they inhabit the soil and leaf litter. Other species of springtails (not snow fleas) live in tree canopies and even on top of water. A moist environment is essential to prevent desiccation. Since they breathe directly through their skin (another difference from insects, who use a trachea), springtails must balance hydration with breathing. Complex structures on their skin trap tiny, durable reservoirs of air.

In their damp habitats, springtails are essential members of the community. What they lack in size, they make up for in numbers. They fragment organic material and make it easier for decomposers to break down. Springtails also curate the soil’s microbial inhabitants by eating bacteria and fungi, and by spreading them around. One common fungus—Laccaria bicolor—has turned the tables on springtails. This fungus paralyzes and decomposes the springtails, then sends their nitrogen over to a white pine through their roots.

On your next adventure in the snowy woods, be sure to keep an eye out for tiny, leaping specks on the snow. They just might be more interesting than you’d expect!

Author’s Note: This article has been updated from 2016. I’m busy building an exhibit!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, April 4, 2024

Protecting Birds from Your Windows

The soft but sickening thud sent out a wave of impacts. Conversation, typing, and higher-level thinking stopped. From four corners of the office, heads instinctively turned toward the sound. Bright morning sunshine streaming through the window illuminated nothing unusual, though. With a mix of hope and dread, I opened the back door and scanned up and down the patio. Nothing. I sighed with relief and stepped back inside.

I’d been expecting to find a small bird—lying either lifeless or stunned and glassy-eyed—at the base of the large row of windows that face the Museum’s back yard. Low-angled sunlight in the spring, in the fall, and early in the day, sneaks under awnings and tints the glass of our windows with stunningly accurate reflections of trees and sky. When little birds try to fly into that scene, they get a painful—and often deadly—surprise.

This juvenile cedar waxwing died after flying into a reflective window. Photo by Emily Stone.

Birds can collide with windows in any season, but I’ve always noticed an increasing number of those sickening thuds in spring. As waves of migrating birds head north, we see both a huge increase in the number of individuals, and an increase in birds who are new to the neighborhood and more likely to be hoodwinked by windows.

According to the Humane Society, roughly half of the birds who hit windows succumb to their injuries or are killed by predators while they’re vulnerable. The thud I heard was from one of the lucky ones who flew away. An estimated 1 billion birds die this way each year.

From the number of calls and emails I get on this topic, I know that these bird deaths weigh heavy on the hearts of many. Not only is it distressing to find feathered corpses outside your home, or to watch the life go out of something so innocent and delicate, but headlines tell us that birds are in global decline due to habitat loss, climate change, and more. Each small life counts toward the whole.

Now that warm days are turning even window washing and yardwork into attractive tasks because they give us excuses to get outside, it’s a good time to think about making your windows better for birds.

Window screens that go on the outside of the glass are one of the best tools for preventing collisions. Not only do they break up the reflection, they also act as a safety net. If your windows didn’t come with bug screens, you can use bird netting from a garden store (meant to keep robins out of your strawberries) instead. Just make sure to pull the netting taut like a trampoline, and keep it at least 3 inches off the window so the birds don’t bottom out.

A purely visual grid can also work well. Using tape, soap, tempera paint, or paint pens, you can add designs to your windows that make the glass visible to birds. If you’re feeling artistic, an intricate doodle would do the trick. Otherwise, using a level and a yardstick, you can simply draw lines. The key is to make the spaces between the lines small enough that birds don’t try to squeak through. For best results, vertical lines should be no more than 4 inches apart, and horizontal lines no more than 2 inches apart. If your casualties include hummingbirds, then use the 2-inch measure all around.

While not practical for everyone, you could make the designs permanent by etching or sandblasting them directly onto the glass. If you’d rather use decals, they need to be just as densely spaced as the grid in order to be effective. A company called CollidEscape makes grids of dots and one-way transparent film that can do the job. But those single, elegant hawk silhouettes have been shown not to work. Likewise, past recommendations about how to safely space bird feeders away from windows haven’t stood up to testing.

You can also combine the ideas of a grid and a screen and make “Zen Curtains.” Basically a grid made of cords; they hang down over the glass on the outside of the window. They can be easier to install than paint, longer lasting, and can be aesthetically pleasing. I’ve seen them made from sparkly string with tiny mirrors attached, and the effect was delightful! A simple internet search will turn up both commercial and DIY versions.

Not every window or every homeowner can accommodate these ideal modifications, though. Using a simpler option, or a combination of techniques, is still helpful. At the Museum, we often tape a single length of curling ribbon at the top center of each window. As the ribbon blows and bounces in the breeze, it helps to deter birds. Awnings, external sunshades, and shutters can also minimize reflections. Having flowers and shrubs at the base of windows can encourage birds to dive in for shelter instead of trying to fly through to escape from a predator.

Making changes indoors can have an impact, too. Blinds, shades, or even sheer curtains on large windows change the reflection quite effectively. And my favorite recommendation is one of the easiest: letting your windows stay slightly dirty can cut down on the realism of the reflection.

Recent research found a positive relationship between the diversity of bird species in a neighborhood and the life satisfaction of people who live there. Add that to the reduction in those sickening thuds, and bird-proofing our windows feels like a great way to increase happiness this spring.

Author’s Note: This article is reprinted from 2021. I’m busy building an exhibit!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Summer Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Friday, March 29, 2024

A Trend of Predaceous Diving Beetles

As a naturalist, I get the strangest emails. I try not to check them at home, but when my phone buzzed and the subject said “June bug on steroids?” it was worth interrupting my evening chores. “The past couple nights I’ve heard something hit our window at night when we have lights on and each time I’ve thought ‘that sounded like a June bug… but BIGGER.’” wrote a Museum member.

I opened the video, and sure enough, there was a black, oval-shaped beetle about an inch and a half long walking along the boards of a deck. The message continued, “I’ve never seen a beetle so big here in the Northwoods. Hopefully it’s not a sign that all of the bugs will be mega sized this year after such a weird winter.” Chuckling, I wrote her back, “Looks like a predaceous diving beetle! That’s their normal size!” The next day, I was scrolling through a Facebook group of regional nature observations, when a video of a diving beetle squirming in a bucket popped up with the caption “Biggest June bug ever!!!” Since June bugs are actually beetles, too, I applauded them for getting close.

Predaceous diving beetles regularly fly between bodies of water, and these 1.5 inch-long insects have been observed around homes recently. June bugs look similar, but are only an inch long and don’t have the large, paddle-like back legs of their aquatic cousins.

Have you heard the saying, “two is a coincidence, three’s a trend”? Arriving home from work, a black spot on the shrinking pile of snow near my front door caught my eye. Yep, there was a predaceous diving beetle! Despite being chilled, he was very wiggly once I flipped him over. There was a wide patch on his front leg, which is a character of the males only. I snapped some photos and then scooped him into a bucket, walked him down the hill, and released him near the lake. As luck would have it, a north wind had blown all the remaining ice up against my shore, so there wasn’t access to water. But I put the beetle on bare sand to let him warm up. He must have flown to my driveway; hopefully he can fly the last leg to the lake!

Since dispersing diving beetles have become a trend, it’s clearly my sign to write about them. Have you also encountered one recently?

Usually, you’d expect to see predaceous diving beetles swimming near the shallow edges of ponds and streams where there are plenty of aquatic plants to lay their eggs on, and few insectivorous fish. Their larvae are aquatic, but crawl out of the water to pupate in mud along the shore. Metamorphosis takes about a week, and they crawl right back into the water as adults.

Their continued surf-and-turf flexibility comes in handy if their little pond starts to dry up. Like most beetles, PDBs hide a pair of shimmering hindwings under an armored set of forewings called elytra. When all of their wings are closed, there’s a seam straight down the middle of their back. When open, the elytra look like the doors of the DeLorean in Back to the Future. The two cellophane-like hindwings pop out from underneath to flap away, with their large body and their hairy, paddle-like legs – adapted for swimming – dangling awkwardly.

The elytra don’t just hide more wings, they also trap a bubble of air next to the beetle’s breathing pores, which happen to be located on their rear end. The bubble is precisely sized to sustain their dive while not floating them back to the surface. Once the all of the oxygen has been gleaned from the air pocket (which reportedly takes somewhere between 10 minutes and 36 hours), the beetle swims up to the surface for a resupply. Sometimes they’ll climb fully out of the water and slather a layer of anti-microbial goo around their spiracles to keep their respiratory system healthy. Beetle larvae also have to return to the surface periodically to sip more air, which they store in their tracheal trunk. This handy storage vessel is similar to our windpipe.

Both the larvae and adults are fierce predators. PDB larvae have earned the nickname “water tigers” by ambush hunting with jaws open wide. Once they pounce, digestive enzymes flow through channels in their sharp pincers into the prey, turning the captive’s insides to goo. The larva then sucks out the prey smoothie. Although rarely seen because they tend to hide in the mud, the larvae occasionally bite humans. That their bites are described as “painful, but not medically important” is only mildly comforting. More comforting is the fact that they eat a lot of mosquito larvae.

Adult beetles are often credited with the same digestive enzyme injecting powers, but the most reliable sources I found described them as merely chewers and shredders. They often eat dead stuff, or they might sneak up on or even chase down insects, leeches, snails, tadpoles, small fish, AND mosquito larvae!

So what are these aquatic beetles doing on our decks, cars, and snow piles? Some species, especially those who tend to live in shallow ponds, change locations frequently, and often en masse! Has this dry spring forced them to leave shrinking pools? PDBs are also known to disperse to avoid parasites in their former home, predation, crowding, and competition from their buddies, and even a lack of plants.

Moonlight reflecting off water is a beacon for dispersing beetles, but this means that yard lights, cozy windows, wet roads, puddles, and shiny cars can lure them astray. These fast swimmers are slow and vulnerable on land, which benefits raccoons, skunks, snakes, and other little predators.

As they are flying around, predaceous diving beetles become somewhat waterproof, and may have trouble breaking through the surface tension of their hopeful new home. One way they resolve this is to exude “wetting agents” that breaks the surface tension, similar to dish soap. The more fun option is to dive in at high speed.

If one happens to dive toward your window, the shiny roof of your car, or some other reflective surface, at least now you know that you aren’t seeing June bugs in March.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Winter/Spring Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, March 21, 2024

A Vocabulary of Seeing

“Let’s start with the evergreens,” I told the small group who’d showed up for my tree identification program. Picking up a white pine bough, I plucked off a bundle of needles. “Pines cluster their needles in a group called a fascicle,” I lectured, “and they are held together at the base by a sheath.” Fascicle is one of my favorite botanical words, and I loved watching these newbies roll it around on their tongues. After years of formal training in plant identification, I’ve acquired a lot of vocabulary words that I don’t get to use very often.

I’ve also acquired some silly mnemonics for remembering plant ID. “Notice that these needles come in fascicles of five. That means it’s a white pine. W-H-I-T-E: white has five letters. Five needles, five letters. Also, the growth form of their needles makes white pines look like they have clouds on their branches, and clouds are white.”

White Pine needles come in fascicles of 5.

Folks humored me, nodding their heads in understanding. After examining a couple more evergreens, we turned to the jumble of bare sticks I had spread on the table. To most people it would look like a pile of junk. To me, it looked like a gathering of old friends with easy-to-see differences. The vocabulary started flowing.

Maples, ashes, dogwoods, and viburnums have opposite arrangement. Their twigs and buds sprout directly across from each other in pairs, while other trees place their buds and twigs singly, in an alternate arrangement. This is a good place to start your ID.

Sugar maple buds and twigs are oppositely arranged

Then we check out the buds more closely. Buds are miniature packages of new growth, pre-formed last summer, and just biding time until they can burst open in a flurry of new growth and elongation. Baby leaves, twigs, and flowers may all be crammed into the same bud, or special buds may hold the flowers. Tiny, tough, modified leaves cradle all that tender new growth, protecting it from desiccation. These bud scales give great clues to a plant’s identity. In sugar maples, the bud scales are a rich caramel color, and they are imbricate. Another one of my favorite botany vocab words, imbricate means overlapping like shingles.

These red maple buds have imbricate scales -- like shingles. They are also valvate -- meeting symmetrically like a clamshell. And ciliate margins with an edging of white hairs.

On red maples, the scales are imbricate, but there are fewer of them, and they are arranged symmetrically in pairs. If the scarlet buds and new growth on red maples aren’t enough it give away their ID, the buds also have distinctive “ciliate margins” of tiny white hairs edging each red bud scale.

I could see the gears turning as people squirreled away this information in preparation for the quiz. Shrubs always seem the most difficult to identify in winter, since they’re smaller, and lack the distinctive bark of a paper birch or red pine. But if you look closely, the ID is in the details.

Beaked hazel is one of the most common understory plants in these woods. Also known as “bear nut”, they are an excellent wildlife plant. From afar, they look like any other spindly shrub. Up close, their fuzzy, two-toned buds are quite handsome. Just two or three dark brown, imbricate scales clasp the bottom of the bud.

Beaked hazel buds and catkins identify the common shrub all winter long. Photo by Emily Stone.

The light brown, inner scales toward the tip are almost valvate (a term that means two symmetrical scales that come together like a clamshell.) They are also pubescent. The fine hairs that cover the scales serve to protect the bud from cold and dryness. In the spring—before the leaves unfurl—a tiny, red, octopus flower will sprout from the tip of the bud. In the leafless woods, wind can easily bring it a dusting of pollen. That pollen comes from tiny catkins on the hazel. All winter, the catkins are tan, fuzzy and compact. Any day now, they’ll elongate into pendulous yellow strings of flowers.

Early spring warmth has coaxed the tiny red flowers of beaked hazel to poke out of their buds. Photo by Emily Stone.

These buds and catkins all formed last summer, while leaves still clung to the trees. It’s in the tree’s best interest to make buds while the sun shines, and energy is plentiful. So there is only a brief time—just after spring bud break—when there are no buds to look at.

Fascicles. Arrangement. Imbricate. Ciliate. Valvate. Pubescent. Catkins. This language may seem complicated and excessive, but for humans, to name things is to see things, and vice versa.

In Braiding Sweetgrass, botanist Robin Wall Kimmerer philosophizes about the language of science. “Listening in wild places, we are audience to conversations in a language not our own. I think now that it was a longing to comprehend this language I heard in the woods that led me to science, to learn over the years to speak fluent botany. A tongue that should not, by the way, be mistaken for the language of plants. I did learn another language in science, though, one of careful observation, and an intimate vocabulary that names each little part. To name and describe you must first see, and science polishes the gift of seeing.”

As the students moved away to test their new knowledge, I hung back for a second, savoring the beauty of “see through” season in the leafless woods, and the words I have to see it with.

Author’s note: This article is reprinted from 2015.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Winter/Spring Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, March 14, 2024

Freezer Burn

Reaching into my chest freezer, I pulled out a quart-size zip-top bag full of dark green leaves. Or at least leaves that had once been dark green. The frilly edges of my kale were now a little pale in places, and ice crystals crunched brittlely inside the bag. Last summer I’d harvested grocery bags full of kale from my garden, blanched them briefly in boiling water, and then quenched them in two cold water baths. After stuffing a handful into a baggie, I rolled it from the bottom to squeeze out extra water and air, and firmly pressed the closure.

Despite my best efforts, several months in storage had led to freezer burn. Ice in the leaves had sublimated, turning from solid to gas without passing through the liquid state. The water that was once in the leaves had become the ice crystals in the bag. Unworried, I thawed the kale and chopped it finely to add to a soup simmering on the stove. Freezer burn isn’t dangerous to eat. It can affect the flavor of food, but I wasn’t counting on kale for flavor anyway.

The following day, I headed out for an afternoon walk. With bright sunshine, the temperature had risen just above freezing, but now a brisk wind was making the lengthening shadows quite chilly. As usual, I paused to admire the mosses growing along a steep, north-facing bank. On this day they weren’t very pretty.

Whole patches of moss were crinkled and brown, while others were brown at their tips, and some leaves were ghostly pale…not unlike my freezer burned kale. I nosed around a bit in the moss patch, taking photos and investigating the damage. Later, I emailed Joe Rohrer, Professor Emeritus of Biology, University of Wisconsin-Eau Claire. Joe taught a moss ecology workshop for the Museum in 2019, and will be teaching it again this October.

“Honestly, I can't cite a single academic paper on this topic,” wrote Joe. But he’s also been noticing chatter about this very topic in the moss-themed social media groups he’s part of. “The consensus seems to be that some mosses show winter dieback regularly but sprout new green growth in the spring. The moss gardeners see this a lot with Atrichum and Polytrichum species. The leaves of the previous year do seem to die, but new growth from the tip restores their green color. Other mosses just turn a rather ugly golden brown, such as Thuidium, probably similar to the red coloration we see in some vascular plants when they get winter sun but are shaded during the growing season.”

Uploading my moss photos to iNaturalist to identify them, I was able to confirm that the pattern he outlined seemed to hold true on my driveway.

“My guess is that drying out is probably more harmful than freezing temperatures,” Joe concluded.

And I agreed. One of the benefits of the Subnivean Zone, which never had a chance to truly develop on my driveway this winter, is that a blanket of snow holds moisture close to the soil. According to horticulturists, winter burn is caused by low soil moisture, freezing temperatures, and blowing wind. Not only does that magical space hold the temperature steady near 32 degrees, it also eliminates windchill, and provides a high humidity habitat. Without it, moisture sublimates from the moss leaves just like from my kale.

It's not that mosses haven’t prepared for this. As drought sets in, their cell membranes shrink like vacuum-sealed freezer bags. This winter has been especially rough, though, with many nights below freezing without snow on the ground. Hopefully the mosses were able to synthesize a big enough supply of enzymes for cell repair to manage the damage from this weird winter.

Next to that sad patch of moss were several rosettes of fern leaves. Evergreen wood fern doesn’t die back in the fall. Instead they flatten to the ground and let snow cover them. Concentrated sugars act like antifreeze in temperatures 5-10 degrees below freezing, and special proteins keep them from being damaged as temperatures plummet further. Even in a normal winter, these leaves never stand back up. They are replaced by fresh, new leaves in the spring. But for several months they can continue to do photosynthesis—while leaves are off the trees—and give the plant a head start on new growth. Maybe.

The tips of the evergreen wood fern fronds near my sad mosses are curled up and look dry. Water is essential for photosynthesis. I can’t imagine they are very productive right now, and I wonder if they will even recover if it eventually rains.

Farther up the road, I stopped near another nearly vertical bank. Dozens of wintergreen plants poked stiffly up above the dry brown leaves. They looked pale and dehydrated, just like the ferns. Would their waxy leaves be tough enough to survive the dry cold? They are well-adapted to hunkering down in the Subnivean Zone and even photosynthesizing there. These many weeks of exposure to dry cold must be challenging, even to them.

I wasn’t looking for wintergreen, though. One of my favorite spring flowers, trailing arbutus, grows on this bank, too, but spotting them is always a challenge. Finally, I glimpsed the brighter green, broader leaves peeking out from under the duff. They didn’t look freezer burned. Perhaps the secretive, ground-hugging nature of this little plant is a way to survive winters just like this one. Soon they will bloom, and I’ll plant more kale, and most of the mosses will recover. Soon, this weird winter will be over.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed until May 1 to construct our new exhibit: “Anaamaagon: Under the Snow.” Our Winter/Spring Calendar of Events is open for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.

Thursday, March 7, 2024

Bark Eaters

“Who’s eating my trees?” asked a participant on a hike last week. I’d been wondering the same thing! A few weeks ago I noticed creamy colored exposed wood on several small maple trees along my driveway.

“Why do animals even eat bark?” someone else asked. Good question. Most bark is composed of tough, dead, dry cells that are not very appetizing. Those cells are made of lignin, which makes wood rigid and is very hard for digestive systems to break down. White-rot fungi and a few bacteria are the only organisms who can consume lignin using specialized enzymes. Bark also contains tannins, which are bitter tasting chemicals that can inhibit digestion.

Unappetizing outer bark is how trees protect their slightly more appealing inner bark. In a tree trunk there are several layers of different cells, including xylem and phloem. Xylem, which is dead at maturity, carries water and minerals up from the soil. Old xylem becomes what we think of as wood. The living phloem carries sugars down from the leaves. They have a layer between them called the vascular cambium, which creates new xylem and phloem cells. Cambium is made of undifferentiated cells who can become anything - like stem cells. These three layers are considered the inner bark.

The living cells of the inner bark contain complex carbohydrates, sugars, and minerals. Right now, when the maple sap is running through the xylem, the inner bark is extra sweet! Even in the dead of winter, inner bark was a source of food for the animals who can access it…and digest it.

Porcupines are one likely culprit in the decortication (bark removal) of my trees. The bottoms of their feet are hairless and covered in a pebbly texture that improves their grip. Long, curved fronts claws also aid in tree climbing, along with bristles on the underside of their tail. To get at the most nutritious parts of a twig, porcupines will balance out toward the terminus of a branch and nip off its end using their self-sharpening incisors. Turning the stick around, they nibble off all the most tender twig tips and buds and then discard the rest. Sometimes you’ll see porcupine tooth marks on bigger branches, too, or even the trunk.

With long claws and several other adaptations, porcupines are able to eat seemingly unappetizing tree bark. Photo by Emily Stone.

Hemlocks are their favorite winter food. As spring progresses, porcupines nibble on a buffet of different trees and plants, making sure to eat each one at their point of peak nutrition. Even this careful food selection wouldn’t be enough without one more adaptation: porcupines have an extremely long large intestine filled with microorganisms who produce lots of enzymes. This extended digestion allows porcupines to extract more nutrients from their food.

Reading about porcupine digestion made me curious about their cousins, the beavers. Now, there’s no way that a beaver could have nibbled the bark on the twigs of trees still standing along my driveway, but these two big herbivorous rodents have quite a bit in common, and some important differences. An article in the Canadian Journal of Zoology suggests that beavers don’t chew their food quite as well as porcupines, but make up for it by having a small intestine that’s 70% longer! The porcupine has a longer colon, though, which allows them to absorb more water from their food. That makes sense, given their different habitats.

There’s one other big difference: beavers engage in coprophagy. Beavers will re-ingest their first round of poop so that they can have another go at extracting all possible nutrients.

Beavers share the trait of coprophagy with another bark eater: bunnies. Rabbits and hares have short digestive tracks, so they combine a good microbiome with coprophagy to enhance digestion. Both rabbits and hares eat their first round of soft, greenish cecal pellets, and then leave behind fecal pellets that look like M&Ms made of sawdust. This allows them to eat twigs and inner bark in the winter. Of course, they focus on the bark of small stems at the height of the snowdrifts…not in the tops of trees.

Voles also eat bark low to the ground. These little rodents like to hide in the subnivean zone under the snow and nibble on bark in relative warmth and safety. They can damage trees, even girdling and killing them. Voles have a specialized pouch called a cecum at the beginning of the large intestine that provides a place for food to be fermented. They may also use coprophagy to help absorb certain nutrients.

In comparison, deer have the most complicated gut for digesting bark and twigs. They are ruminants with four stomachs, like cows. Microorganisms in deer’s rumen break down tough materials, aided by them regurgitating and chewing their cud until it’s broken down enough to move on to the rest of the stomachs. Deer might strip bark off a young tree higher than a hare, but not high in the treetops like I’d observed.

So, who was the bark-eating culprit in the trees along my driveway? Judging by the tiny tooth marks, and my most commonly seen neighbors, they were gray squirrels. Squirrels have sharp teeth and excellent climbing skills just like porcupines, and can venture out onto smaller branches to nibble on the most tender bark. Squirrel tooth marks are less than 2 mm wide, while porcupines’ teeth are two to three times that big.

The tiny tooth marks high up on a sugar maple sapling are likely the work of a hungry gray squirrel. Photo by Emily Stone. 

Discarded bark strips litter a log below the decorticated tree.

Recent research suggests that special gut bacteria help gray squirrels extract calcium from tree bark. This adaptation might be what’s allowing gray squirrels to outcompete the native red squirrels in Great Britain, where gray squirrels were introduced. Our native red squirrels have been observed eating bark less frequently than grays, but they are smart enough to know that making a small incision in sugar maple bark this time of year releases another one of bark’s sweet secrets.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our exhibit: “The Northwoods ROCKS!” is open through March 9. Our Winter/Spring Calendar of Events is ready for registration! Follow us on Facebook, Instagram, YouTube, and to see what we are up to.