Thursday, April 15, 2021

The Smells of Spring Rain

I could hear the storm approaching as darkness fell. Low rumbles in the distance provided a bassline for the gentle, percussive music of the first raindrops. From out on my porch, I inhaled deeply.

The pleasantly sharp smell of rain after a dry spell conjures up memories of hot, dark-spotted sidewalks under roller-skates, Little League players scrambling to outrun a cloudburst, and jubilant bodies clad only in swimsuits dancing in a sprinkler system that adults don’t control. Scent molecules trigger a connection straight to the memory center of the brain, bypassing the places where we process language. “Nothing is more memorable than a smell. Still, when we try to describe a smell, words fail us like the fabrications they are,” writes Diane Ackerman in her book “A Natural History of the Senses.”

I can tell you about the joy I feel—and have felt over and over for decades—when cool rain falls on a hot day, but my adjectives for the actual smell, like sharp, invoke some other sense. Scientists estimate that the human nose can detect more than 1 trillion scents. Two-hundred and seventy-five chemicals combine to form the smell of a rose. But even to Shakespeare, Master of Words, a rose just smells sweet.

While we can’t easily parse smells into words, scientists have dissected many scents into their component chemical compounds. Researchers Isabel Joy Bear and R. G. Thomas, for example, analyzed the smell of rain on dry earth and discovered that it originates from an oil that plants produce during dry spells to delay seed germination. During dry weather, the oil is absorbed into rocks and soils. Falling drops liberate the compounds and fling them into the air we breathe. Rain also washes the oil away, giving plants relief from the heat and stimulating growth.

Bear and Thomas named the smell “petrichor,” which comes from the Greek term for rock (petra), and the word for the fluid that flows in the veins of the gods in Greek mythology (ichor). I was smelling the blood of the gods splashed up from the gravel on my driveway. After a few more deep drinks of air, I went back inside.

As I puttered around with my evening routines, the thunder rumbled like an approaching truck, and the sky began to flash almost continuously. Finally, the excitement was too much to miss. I stepped back out onto my covered porch to watch the storm roll in.

Lightning pulsed under the clouds and tree twigs etched an intricate pattern of black-on-white across the southern sky. Raindrops swelled from the original percussive patter to a rush of noise. And then, as the storm moved on, streaks of lighting began to split the northern sky. I followed them to the other side of the porch. The downpour slackened, and the rush resolved into many sounds. Big drops from the eaves splashed into puddles. Little drops from trees pattered onto lacy needles. And medium drops, still coming straight from the sky, spattered onto the mats of oak leaves ironed flat by the winter’s weight of snow.

The scent of petrichor was gone now, washed away by life-giving rain, the chemical spell of dormancy broken, just as the plants had intended. I didn’t even have to inhale deeply to catch a new smell though. This one was cooler, wetter, and sweeter. It brought back happy memories of lilacs in the sunshine and the melancholy smell of autumn leaf piles that have become too soggy for jumping in, but I couldn't find precise words to describe the fragrance. And what was causing it? I took long, curious breaths, as I tried to identify this other smell of rain.

The overwintered oak leaves glittered wetly in light from the house. Built from the sugars of photosynthesis, their leathery bodies have been exposed to bacteria and fungi all winter long. Digestive enzymes from those microbes would have worked—slowly—in the cold, damp of the subnivean zone. Did I now smell the sugars that those decomposers released? Was this the smell of death?

Or maybe the maple trees—sending sugars up from their roots, sending their tiny leaves bursting forth—were exuding the syrupy aura. Was this the smell of new life?

Maybe, I thought, as I watched the rain push brown leaves into the soil and encourage green shoots to rise up from it, they are one and the same.

Dead leaves sink into the soil as new shoots rise up. Both are assisted by the rains of spring. Photo by Emily Stone.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, April 8, 2021

Find a Puddle and Some Happiness

Inhaling deeply, I looked out across the sunny expanse of frozen lake. Squeezing my shoulder blades together, I corrected my computer-hunched posture and felt tension release from the muscles. A vigorous gale tossed through the treetops, but here, on the leeward shore, I felt only a hint of breeze on my cheek. With another deep breath, I began to turn to leave, but an oak leaf caught my eye.

With pointed tips curled up like a cupped hand, the tan-colored leaf had become a tiny boat on a clear puddle at the edge of the ice. As I watched, a sliver of wind snuck down and sent the leaf spinning gracefully to the left. A darker brown birch leaf, diamond-shaped with finely serrated edges, traced the same path across the puddle, and its tip slid in to catch a lobe of the oak leaf. Like a pair of dancers, the two leaves twirled and glided on the puddle, pushed by the chaotic wisps of breeze. Such playful movements made me smile.

When I’d stood up from my computer in a huff a few minutes earlier, vexed by the trickle of spam emails that kept interrupting my thoughts and cursing the people who sent them, I wasn’t sure that a walk would help. Research shows that people tend to underestimate how good a simple walk outside will make them feel. But, as I climbed up from the shore, I caught myself smiling at the sunny carpet of mosses who had wasted no time in waking up from winter.

Mosses and a lichens wake up quickly from the long winter. 

That warm fuzzy feeling I was having toward the moss actually has a name: biophilia.

Edward O. Wilson, a revered ecologist and champion of biodiversity, made the term popular, and defined it as “the innately emotional affiliation of human beings to other living organisms." He hypothesized that our love of nature has helped humans survive, and helps us feel connected to all life.

As I sauntered down my long, winding, woodsy, driveway, even more benefits of this biophilia were at work on my brain. The way my eyes scanned the forest, noticing the red buds of a maple tree against the blue sky, the gentle curves of the forest floor that will soon be hidden by new growth, and the patterns of moss and lichens that carpet the side-hill, leads to something that scientists call “soft fascination.”

Pixie cup lichens are one of my favorite beings to notice on the forest floor...

Soft fascination—as opposed to the “hard fascination” of something like a sports event or movie that demand full attention—requires no effort and leaves space for reflection without risking boredom. Soft fascination leads to clearer thinking, reduces anxiety, and restores our ability to focus on tasks later. While our mind wanders, we may end up solving problems or coming up with creative ideas. Research also shows that people tend not to ruminate on the bad stuff that causes anxiety while in nature.

In addition to watching leaves dance on a breeze-tickled puddle, sunsets, rain showers, parks, and forest paths are all opportunities to experience the brain-resting effects of soft fascination. Just be sure to leave your phone out of reach: talking while walking ruins the effect.

The benefits of time spent outside, especially in green nature, are especially noticeable for people who have attention-deficit/hyperactivity disorder (ADHD). During an experiment at the University of Illinois, kids who took just a 20-minute walk in a park had their symptoms of ADHD reduced by threefold. That improvement was roughly equal to the difference in having ADHD or not having it, or of not being medicated vs. experiencing the peak effects of a common medication.

Not only do kids show improvement in focus and memory when they get to be outside, they may also show less anxiety, depression and aggression than when they are indoors in a restrictive environment. Erin Kenny, founder of a nature school, put it this way: "Children cannot bounce off the walls if we take away the walls."

Adults aren’t much different. I’d been bouncing off my mental walls at the computer all afternoon, and now a short walk was completely changing my mood. The chickadees were helping. “Hey Sweetie!” came their cheerful whistles from the hemlock twigs above my head. I’ve been using the calls of chickadees to cheer me up ever since a particularly stressful week back in college.

I’m not the only one. Psychologists have found good evidence that bird songs improve mood and mental alertness—listening to recorded bird songs helped reduce that post-lunch slump in elementary students. And in a different study, scientists found that a 10 percent increase in neighborhood bird songs translated into an increase in life satisfaction usually equated with a 10 percent increase in income.

It’s not really breaking news anymore that relaxing in nature makes us happier, but it is worth repeating. Nature relieves mild depression, reduces stress, and increases happiness for both adults and children. And, without the icy winds of January or the mosquitoes-hordes of July, this is the perfect season to walk slowly through nature. Go find a puddle, a leaf, a breeze, and some birdsong, and you will also find an increase in well-being.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, April 1, 2021

The Lessons of a Northwoods Spring

“I still fear that the cold will return. I am still full of uncertainties.”

When Toni Alioto wrote that line, she was imagining a whimsical conversation between Spring and Winter as they negotiated the vacillating weather patterns common in a Northwoods March. It’s the same fickle weather I’ve been writing about lately in the context of wood frogs and fat bikes. She crafted this line as part of an assignment for “Writing the Environmental Essay,” a class I’m teaching in a condensed and totally virtual format for Northland College this semester.

Toni assured me during class discussion that her personification of spring was focused purely on the weather. But with her mention of fear and uncertainties, my mind jumped straight to the pandemic.

By the time you read this, all Museum staff members will have received both shots of the vaccine. Many of you already know—or are anticipating—the incredible sense of relief this protection brings. A weight is being lifted from our shoulders. As I watch the bright sun and gentle rains release the landscape from a burden of heavy, restrictive snow, I can’t help but compare this stage of the pandemic to this moment in spring.

With the snowdrifts shrinking back into the shadows, the Museum staff are letting tentative hopes and plans emerge. We’ve set a date for when the Museum will open to the public for the first time in months. We’re dreaming up ideas for summer programs. I’m giddy at the thought of tramping around the woods with other humans there to share my joy and amplify each other’s curiosity.

And yet, we all know that winter could return at any moment. Late spring blizzards have left ice in the corners in our collective memory. Previous surges of the virus, and the lives and livelihoods they ended, have left pain in our collective heart. While some news looks hopeful, the meteorologists and the Centers for Disease Control (CDC) both pepper their sunny forecasts with that cautionary “unless…”

So, with hope and fear doing battle in my chest, I made a few clicks and watched Toni’s essay fade from my screen. That warm rain I mentioned had just tapered off, and I wanted to see what nature could teach me about life emerging into a tenuous spring.

The twig of a serviceberry bush caught my eye first. Tiny, wrinkled leaves were bursting forth from the pointed clasp of burgundy-colored bud scales. I worried for a second, tugging my jacket closer at an unexpected gust, and thinking that the leaves were emerging from their protective isolation too soon. Looking closer, though, I found a thick weave of white hairs. Surely this cottony coat will protect the serviceberry from a freezing swing back to winter, just like our masks protect us as we emerge into uncertainty.

Serviceberry shrubs protect their early emerging leaves from cold snaps with thick fuzz.
Photo by Emily Stone.

Next, I looked down. On the shady cut bank of my driveway, the lush patterns of moss rest on the high, angled slope like artwork displayed on an easel. The contrast of their vibrant green leaves with the dark browns of decay pulled me closer, and closer, until my knees were wet and my camera invaded their Lilliputian personal space.

Even at close range, the moss looked unfazed by winter.

There are several secrets to moss’s resiliency. Most visible, perhaps, is their tendency to lie low. Mosses find a good place and stay there. They don’t need to flit about like butterflies—braving air filled with dangers like freezing temps and hungry mouths—in order to find food or companionship. When the snow comes and seals them in, the mosses take full advantage of the protection it provides from cold, dry air.

Moss has many adaptations to help it survive long Northwoods winters. Photo by Emily Stone.

Mosses are not immune to the challenges of a long winter (or drought) of dormancy, but they do know how to prepare. As their leaves dry, cell membranes shrink like a vacuum-sealed freezer bag. Essential functions shut down. And, with amazing “forethought,” the mosses synthesize and store away the enzymes of cell repair that will manage the damage of desiccation. And how would these mosses fare during that late spring blizzard? Their willingness to stay small and their stockpile of specialized chemicals will bring them through unscathed.

It’s not hard to see the parallels between moss in winter and humans in lockdown. We stayed put and tried to get cozy. We made hard decisions about what functions could and could not be shut down. And we also created and replenished the stores of medicines that help prevent and repair damage. Even as we enjoy the current freedom from the heavy snow, those tools will need to remain at hand.

I took a deep breath. Going outside hadn’t resolved all uncertainties, but it did loosen the knot of worry in my chest. Nature itself is a tool we can use to stay healthy and happy. While the weather may do a wild dance on its way toward summer, it can also remind us that being prepared for the unexpected, whether that means having fuzzy buds, laying low, bringing an extra jacket, or continuing to wear a mask, is something a Northwoods spring has already taught us all to do.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, March 25, 2021

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.

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.

This juvenile cedar waxwing died after flying into a reflective window during the fall of 2011. A bumper crop of fermenting black cherries in the nearby trees made the problem even worse that year. Read more about it here. Photo by Emily Stone.

According to the American Bird Conservancy, 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.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, March 18, 2021

Spring is just around the corner—and winter is, too!

The metal studs on my fat bike tires crunched noisily on the trail as I pedaled furiously toward the top of a hill. Reaching the crest, I sized up the view, crouched low over the seat, and zoomed down. The air rushing past my face was chilly, but intense spring sunlight and tough pedaling on the slopes of the Esker Trail near Cable were keeping me plenty warm.

Several sunny afternoons in a row had softened the snow of the expertly groomed trail, and I had started my ride early to take advantage of overnight temperatures in the teens that had solidified the surface again. Now, with a firm, sidewalk-smooth path, gravity-fed momentum carried me almost all the way up the other side.

Overnight lows have frozen the Esker Trail solid, but bright sunshine will make the afternoon feel like spring. Photo by Emily Stone.

A few minutes later, I was reveling in the easy riding when I suddenly found myself tipped over with my left leg sunk up to the knee in drifts. This section of trail was contouring around the side of a steep hill. Winding switchbacks and curves had befuddled my sense of direction long ago, but I knew that the hill must be facing north. On this corner, it was still winter. No glaring sun had hardened the surface, and I’d skidded out in soft fluff. My leg sank into snow that was as light and airy as January.

On the previous, sunny afternoon, the mercury had risen to almost 40 degrees, and I’d been cross-country skiing instead. The fish scales in my kick zone work rather well on warm snow, and I hummed along merrily for a kilometer or two. Then, suddenly I found myself slipping and sliding up a relatively gentle hill. The slope wasn’t getting direct sun, but I could still see light glinting off a coating of ice in the tracks. Once again, even with my sense of direction lost in the winding trails, the iciness of the hill gave away its bearing. In contrast, I had to squint against glare as I began the next downhill, and I almost fell over when a section of slush caught my skis.

Late-afternoon sunshine glints off icy ski tracks at the North End Ski Trail in Cable, WI.
Photo by Emily Stone.

A few days later, I went to bed with the sound of rain and thunder, and woke up to a world dusted in snow.

What I’m trying to illustrate, you may have guessed, is that this time of year is both winter and spring. Sometimes the two seasons are separated by a few feet, and sometimes the difference is in a few hours.

Outdoor enthusiasts pay close attention to this heterogeneity. Fat bikers wake early. Road bikers time their rides to hit the warmest peak of a sunny afternoon. Skiers brace themselves for sudden changes in speed. Maple tree tappers carefully monitor temperature changes, too. They know that the sap flows best when nights are cold and days are warm; when an afternoon feels like spring, but winter returns with the dark.

Nature, of course, has no choice but to factor the fickleness of spring into her calculations. Trees who leaf out early in response to unseasonable warmth may then lose all of those leaves to frost, or may surrender entire branches if those leaves catch heavy, wet snow. They must hedge their bets and not be fooled. According to Bernd Heinrich in his book “Winter World,” “Buds follow local schedules that are dictated by an interplay of cues involving day length, seasonal duration of cold exposure, and warmth. Warmth alone is not enough.”

And warmth can also vary quite dramatically from one side of a hill to the other. North-facing slopes receive very little heat from the low-angled winter sun. Even throughout the summer they remain shaded and cool, with less evaporation than their south-facing counterparts. Eastern aspects are similar, since they receive sun in the morning, when temperatures are lower. Western slopes, however, receive the full blast of the sun at the warmest time of day.

These variations in temperature by space and time are not a global phenomenon. Seasons are a characteristic of the temperate zone. The direction a hill faces only really matters in these same mid-latitudes. Near the equator, the sun is overhead and touches everything, all year. Near the poles, winter sun is too weak to provide much warmth and the summer sun circles around and shines on everything. But in latitudes from the bottom of Mississippi to the top of Manitoba (and the corresponding latitudes in the southern hemisphere) slope aspect impacts sunshine, evaporation, soil moisture, and soil temperature…and the plants who grow there, too.

The variety we experience in the Northwoods—the way you can find an early wildflower in a sunny spot and a late one in the shade; the short scramble it takes to get from a dry oak slope to a damp hemlock ravine; the change from winter to spring and back in a single day or a single corner or a single hill—is one of the my favorite parts of living here. At this time of year, it feels like spring is just around the corner…and winter is, too!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, March 11, 2021

Wood Frog Winter

The snow is melting, the soil is warming…and I can’t decide if that’s good or bad. The classic tracks on my favorite ski trail were in fantastic shape last week, and I may or may not have let out a little whoop on a long, swooping, rollercoaster of a hill. But at least a smidge of my smile could be attributed to the southwest-facing bank that cradled the trail and the happy little mosses there whom the sun had recently unveiled.

Huge thanks to the volunteer groomers at the North End Ski Trail!
Their trail maintenance efforts in all seasons have a huge impact on my winter happiness :-)

Oodles of my favorite beings—like moss--live under the snow, in that magical space called the subnivean zone. Like many enchanted things, the subnivium is ephemeral. It comes into existence once 6 to 8 inches of snow accumulate, and disappears again in spring. I love imagining the scurrying mice, hunting weasels, creeping spiders, and gnawing fungi who stay active down there, as well as the mosses, roots, seeds, insects, and others who sleep soundly under the temperature-moderating blanket of white.

In fairytales, it’s a true love’s kiss that breaks the sleeping spell. In nature, it’s often warmth from the sun. The moss has felt it. Sugar maples are feeling it. Who’s next?

Last fall, wood frogs hunkered down in the duff to wait out winter. In order to wake up early, they don’t dig very deep. Even in the relative warmth of the subnivean zone, this means that the frogs must tolerate being frozen. In the depths of winter, up to 65–70% of each frog’s total body water is ice (any more than that and they’re dead). With the kiss of sun and rain, wood frogs thaw from the inside out.

Recovery is relatively rapid—especially considering what the frogs have been through—but not instant. After a day they can move. After a couple days, they’re ready to mate. But even as the black-masked amphibians hop toward a woodland pool, they still aren’t ready to eat. There are a few possible reasons for this. First, it’s quite a process to freeze and then thaw, and their digestive system may be the last system to come back online. Second, there’s not much food available in April when wetlands’ icy caps have just softened and snow may still rest in the shade. Third, the way a wood frog spends the winter is centered on getting back to their breeding ponds ASAP in the spring. Why waste time searching for food?

I get hungry just thinking about it. Wood frogs stopped eating days before burrowing into their hibernaculum last fall, and they will continue to fast until after they’ve gone through the rigors of breeding. Males have to shout at the top of their lungs, chase after females, grip any prospective mate tightly, and fertilize her eggs—all without a snack. Females don’t sing much, but they do lay between one- and three-thousand eggs more than five months after their last meal.

In thinking about this feat of fasting, I had always assumed that frozen wood frogs weren’t using any energy while in their frogcicle state. I was wrong. Frogs’ metabolisms continue to run very slowly even while they are frozen, and freeze-thaw cycles are quite taxing. Researcher Megan Fitzpatrick set me straight when I called her to talk about a research paper published last August in the journal Global Change Biology, and presented at the recent Wisconsin Chapter of the Wildlife Society meeting.

Working with modeling gurus at UW-Madison, Megan created a model to predict how overwintering wood frogs will fare in the face of climate change. Luckily, she didn’t have to start from scratch. The other researchers had already created models about the subnivean zone and regional weather. Those data could be combined with a few of the major Global Climate Models—the ones cited in the news when we talk about how fast different parts of the world will warm—to predict how soil temperature will increase, and how snow cover will change across the southern part of the wood frog’s range.

Megan took those big models and added frog-specific data from a project in Canada that had measured how much energy wood frogs use over the course of a winter. The frogs had been placed in sealed boxes with comfy bedding, cooled slowly, and then subjected to freezing and thawing while the researchers measured their carbon dioxide output as an indicator of energy use.

(Megan assured me that the cold frogs would already be dormant by the time they froze, and therefore would not make the same agonized face as Han Solo as he was lowered into the carbon-freezing chamber in The Empire Strikes Back. Also, all research labs have animal care and use policies to make sure that the critters are treated humanely.)

That study found that carbon dioxide increased sharply at three points: as the frogs were preparing to freeze; as they responded to freezing, and as they thawed and began normal body function and repair. The longer frogs stay thawed in the fall, and the more times they experience freeze-thaw cycles, the more energy they waste. Somewhat counterintuitively, warmer soils going into winter mean that the frogs expend more energy throughout winter.

I asked Megan to explain how that data becomes part of the model. “We break down the steps and each one becomes a mathematical equation that we can add to the model,” she told me. Steps include things like heat flowing through snow, heat flowing into the frog, ice melting in the frog, and the frog’s response to those temperature changes.

According to Megan’s model, warming soils mean higher energy expenditures for wood frogs during winter. But earlier snowmelt means that frogs will survive winter with a balanced energy budget in most regions—or even come out ahead—because winters will become so short. (Notably, her study wasn’t set up to tell us how climate change will impact the frogs during the rest of the year.)

Not all regions saw a balanced energy budget for frogs, though. In the snow belts of northern Wisconsin and Minnesota—where deep drifts tend to linger—wood frogs are predicted to use about 10% more energy to get through a northern winter by the late 21st century. Megan doesn’t think that will kill the frogs, but what about sub-lethal impacts? One study in Michigan found that females laid fewer eggs after warmer winters. And what if a warmer spring means that their ponds dry up? Science is an iterative process that gives us new questions with each study, in addition to useful answers.

Questions like, “the snow is melting, and the soil is warming…is that good or bad for wood frogs?”

So many of the videos out there are overly dramatic--and talk like wood frogs only live in Alaska. Harumph! This is one is concise at least. Just don't pay attention to the last line "science can not yet explain." Science doesn't know everything about wood frogs, but it knows a LOT!

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, March 4, 2021

Shining a Light on Curiosity

Once upon a time, in the cool, dark air of his own backyard, a forestry professor swept the beam of a UV flashlight through the trees. He wanted to know if gray tree frogs fluoresce. They don’t. But when a furry shape found its way into the beam and glowed hot pink, Jon Martin discovered that flying squirrels do.

This serendipitous discovery in May of 2017—spurred on by a bit of previous knowledge and a scientist’s curiosity—sent Jon (a professor at Northland College in Ashland, Wisconsin) and his colleagues on quite the scientific journey.

African springhares (center) are the most recent animals to reveal biofluorescent fur. The discovery that flying squirrels (left) fluoresce hot pink, led scientists from Northland College down a vibrantly glowing rabbit hole. Cyan-fluorescing platypuses (right) are one of their other curious discoveries. Images from Kohler et al, Olson et al, and Anich et al. Compilation by Allison Kohler.

In 2018 and 2019, faculty from Northland College descended into the collections of the Field Museum of Natural History in Chicago to examine the flying squirrel specimens stored there. The interdisciplinary team was determined to learn more about Jon’s discovery that flying squirrels fluoresce under UV light.

After shining their UV flashlights at specimens of all three species of North American flying squirrels and being rewarded by flashes of pink, the next question was “what else?” Previously, opossums were the only mammals known to fluoresce. But, opossums are weird. And although their fluorescence was discovered in the 1980s, no one, it seems, dug much deeper. Where was their sense of curiosity?

The Northland College crew was curious. Would the startling trait be common among other furry critters? As it turns out, platypuses (who are even weirder than opossums) biofluoresce, too, and the Northland scientists published that discovery last October.

During their black light safari through the collections, the scientists logically sought out the cabinet that held Old World flying squirrels, who live in Europe and Asia, as well as “scaly-tailed squirrels,” who aren’t squirrels at all, but small rodents from central Africa with a similar stretch of skin and ability to glide. No glow for the scaly-tailed squirrels. The scientists really didn’t expect EVERY species to fluoresce, acknowledged natural resources professor Erik Olson, as he recapped the story for me recently.

But as the next drawer in the cabinet slid open, flaming orange fluorescence flickered under the flashlight’s beam. “We’ve got one!” someone exclaimed, without even knowing exactly what the drawer held.

The specimens were of African springhares, as it turns out. That discovery was just published in the journal “Scientific Reports.” The authors include Jon, Erik, and also Northland College chemists Michaela Carlson and Sharon Anthony, mammologist Paula Anich, and microbiologist Alissa Hulstrand, among others.

Springhares, I’ve learned, are rabbit-sized rodents who leap like kangaroos, but lack a pouch. They are close relatives of the scaly-tailed squirrels, which is why their drawer was nearby. They live only in Africa, where they forage under the cover of darkness and not much else; not even with friends to help keep an eye out for danger.

On a field trip to the Henry Doorly Zoo in Omaha, Nebraska, the team confirmed that living springhares fluoresce even more brightly than the decades-old specimens. Erik also noted that the springhares—both living and dead—glowed much more vibrantly in person than in the published photographs, where the researchers’ careful, scientific process had captured a narrower range of wavelengths.

There is much left to learn about biofluorescence in mammals. Describing the trait is just the first step, but figuring out what the trait means is quite another process. Does it have ecological benefits? Is it a disease response? Might it be useful for conservation? Or could it possibly have no purpose whatsoever? It will take a bevy of scientists from different disciplines to begin to answer those questions.

“To me it’s just exciting to be part of the description of a trait that was unknown.” Erik told me—especially since the animals themselves are all common and well-studied. “These kinds of discoveries really enhance the sense of awe we have for the natural world; they give us a moment to pause and reflect on the world around us.”

Erik was initially skeptical and cautious when Jon told him about the pink flying squirrels in his backyard. Jon wouldn’t give up, though, and the rest is history. The rest has also been covered in the “New York Times,” published in the “Journal of Mammalogy,” and has captured the imaginations of both scientists and the public.

And it all started…once upon a time…with a particularly persistent forester who let his curiosity run wild in his own backyard.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, February 25, 2021

Curiosity, Perseverance, and Life

There’s a space kid inside almost every one of us. That fact is made clear to me by the nation’s giddy response to NASA’s most recent accomplishment—a successful landing of the Perseverance rover on Mars. The rover used a heat shield, a parachute, cameras, and a rocket-powered jetpack to land. Actually, the jetpack allowed the main contraption to hover while the rover was lowered gently to the surface on a cable. Whaddya wanna bet that next summer there will be kids making rocket noises while they drop the requisite bucket-on-a-rope out of their treehouses?

Perseverance Touching Down on Mars (Illustration): An illustration of NASA’s Perseverance rover landing safely on Mars. Hundreds of critical events must execute perfectly and exactly on time for the rover to land safely on Feb. 18, 2021. Credit: NASA/JPL-Caltech.

While that bucket is probably hoping for a delivery of cookies, Perseverance is looking for signs of life. Its landing area includes a delta—which is a place where a river carrying sediments from its entire watershed flowed into a lake, slowed down, and dropped most of its load in a fan-shaped landform. If there was life on Mars, surely signs of it would have been collected by the river and deposited here. The shoreline of the lake could be another hotspot, based on what we know about life and fossilization here on Earth.

Using another trick straight out of our 10-year-old dreams, scientists can tell the rover to shoot a laser beam at any promising rock and then analyze the chemical composition of the dust cloud that rises. If the rock warrants a closer look, then an x-ray beam and another laser will take a peek at the chemicals present. In the most promising spots, the rover will drill down and collect a piece of the planet. What then? The sample will be stored in a box full of neat rocks (who among us doesn’t have one of those in the basement or garage?) that a future mission of the European Space Agency will bring back to Earth.

Signs of life could include minerals that don’t tend to form on their own, or structures that often form in the presence of critters. There’s an example of one of those structures on Old Grade Road northeast of Lake Namakagon. The Grandview Boulder is taller than a person, and under the moss you can see thin, convex layers in the rock. These layers are the fossilized remains of colonies of photosynthetic microbes. The algae and cyanobacteria excreted mucus, which trapped sediment and eventually built their own rock—called a stromatolite.

The Grandview Boulder near Lake Namakagon exhibits thinly layered structures that scientists are now looking for on Mars. Photo by Emily Stone.

Stromatolites are common in the fossil record on Earth, but rare to find still living. And while discovering a rock with this pattern on Mars would be exciting, it isn’t a sure thing. Stromatolites can also form without the help of life.

So, it’s going to take something pretty special to give scientists complete confidence that they’ve discovered extraterrestrial life.

There’s another problem, too. What if life on Mars looks so different from life on Earth that we don’t even recognize it?

I tackled this problem myself once, as a middle schooler at Girl Scout Camp. The Girl Scouts had a partnership with NASA, and one of the activities they provided was a variation on an activity often called “Create-A-Creature.” Each girl was assigned to a different planet and given a description of the habitat there. All rock, all gas, no atmosphere, crushing gravity, toxic chemicals—there was a stunning array of characteristics among our planets and their moons. Next, we were given a box full of bottles, cans, yogurt cups, and all manner of random stuff scavenged out of the recycling bin, plus glue, pipe cleaners, and other standard craft supplies. The goal? Create a creature with adaptations that allow it to survive on our assigned planet.

Our assemblages of detritus didn’t look like much in fact, but in our minds they had rock-crushing teeth, sulfur-digesting guts, and all sorts of fantastical adaptations that have not yet evolved on Earth. That combination of crafts, space, and tons of imagination was a winning combination for the child that was me. Honestly, the space part wasn’t why I loved it, but the other two ingredients won me over.

I have since led this activity with my own students in many forms. On “Tidepool Day” in California, for example, we built sea creatures using both trash and natural objects scavenged from the wrack line left by high tide. And yesterday, just hours before the Perseverance landed, I led 5th graders in creating their own special fish during a Virtual MuseumMobile visit.

Because we don’t really know what life on Mars would look like if it did, in fact, exist, those NASA scientists need a special combination of skills and imagination. Waddya wanna bet that those NASA scientists and engineers were once kids who created things out of the recycling bin, made rocket sounds in treehouses, collected buckets of neat rocks in their garage, and crick stomped in rocky streams?

Waddya wanna bet that the NEXT generation of NASA scientists is doing those things right now?

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, February 18, 2021

Subnivean Party

Kerflumpf. Mumpf. Fump. It’s difficult to describe exactly the sound that snowshoes make in 18 inches of fresh, fluffy snow. I can tell you that the soundtrack includes some huffing and puffing, and the swish, swish, swish of nylon sleeves as arms swing their assistance. At the start of our recent dive into the polar vortex, I traded skis for snowshoes and headed out into the untracked forest.

Only snow-plops blown out of treetops marred these smooth drifts of snow.
Photo by Emily Stone.

The woods felt peaceful and serene. Only snow-plops blown out of treetops marred the smooth drifts. Winter, I thought to myself, can feel pretty lonely sometimes. If only I was smaller…

Because, for the little critters at least, there is a party going on under there. Under where? In a curious space called the subnivean zone.

Do you remember the magic of hoar frost that I wrote about a few weeks ago? Water vapor in the air crystalizes directly into ice without going through the liquid phase. Under the snow, at ground level, the opposite happens. Latent heat from the earth—stored months ago during days of summer sunshine—gives snow crystals at ground level just enough energy to vaporize back into their gaseous form. Sublimation is the scientists’ term.

The vapor rises just a bit, filtering into the snow, where it changes the structures of crystals as it solidifies again. The result is a zone of airy pockets and loose, granular snow topped by an icy ceiling; and above that a thick, insulating blanket made—counterintuitively—of ice and air. Best of all, this magical space remains at or near freezing. That might not usually seem warm, but after our weeks of subzero temps, we can probably agree that 32 degrees Fahrenheit sounds fairly pleasant.

I’ve written and taught about this subnivean zone many times before. Usually my focus is on the small mammals—mice, voles, and shrews—who make their winter homes in tunnels sewn between soil and snow. And, of course, there are the charismatic carnivores who chase those warm nuggets of protein. Short-tailed weasels (who become ermine in their white winter fur) follow mice directly into their dens. Foxes and owls take another route—pinpointing supper with their ears and then plunging in from above.

But I mentioned a party going on under the snow, and these are only the most visible revelers. Jon Pauli, a winter ecologist from UW-Madison, explains that, “In this refuge, there's a complex ecosystem of interacting microbes, insects, plants and animals that we can't see but are active throughout the winter.” In fact, says one of his research papers, the subnivium is where the “majority of biodiversity in northern temperate areas spends the winter.”

For example, Pauli and his colleagues have been studying the impacts of warming winters on the energy budget of wood frogs. These cold-blooded amphibians take refuge in leaf litter and very carefully allow themselves to freeze solid while the subnivean zone forms around them. Once frozen, their metabolisms are shut down, which preserves their limited energy stores. The moderating effects of the subnivium buffer them from energetically costly freeze-thaw cycles, and also reduce the potential for lethally low temperatures.

Frozen wood frogs have a fair amount of company. One group of ants, in the genus Temnothorax, likes to set up house inside empty acorn shells. Like a colonial version of hermit crabs, they compete for a limited number of good homes. Loathe to abandon their nut hut for the winter, they simply snuggle up with about 100 workers and a few larvae and produce glycerol as an antifreeze to prevent cell damage. Unsurprisingly, colonies in acorns that are buried more deeply in the leaves and soil have higher winter survival rates. Also unsurprisingly, the little girl in me loves that nature has its own version of acorn fairies.

Temnothoraz ants are also known as “acorn ants” because their colonies live inside acorn shells. Photo by Matt Hamer, Wikimedia Commons.

A thick layer of leaf litter isn’t just important for ants. Autumn leaves provide insulation before snow accumulates, and then continue to augment our fluffy white blankets. This protects plants’ roots from freeze damage. Dead leaves also provide essential habitat for woolly bear caterpillars, mourning cloak butterflies, luna moth cocoons, the eggs of red-banded hairstreaks, bumblebee queens, spiders, snails, millipedes, mites, and more. Some of them are frozen, some of them are active. And they aren’t the smallest subnivean inhabitants.

Woolly bear caterpillars need thick leaf litter covered by insulating snow in order to survive the winter. Photo by Emily Stone.

The microbes that Pauli mentioned are important here, too. Fungi and bacteria take advantage of the microclimate of the subnivean zone to slowly break down dead stuff throughout the winter. They release their nutrients in spring—just in time to fuel the growing season. In contrast, invasive earthworms decimate the leaves too quickly. Both insulation and nutrients diminish.

As I was saying, the soundtrack above the snowpack is pretty quiet. That allows me to cock my ears like a fox and focus my listening toward a hidden world beneath the snow. What do I hear? A wild party in that magical place we call the subnivean zone.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, February 11, 2021

Patterns of Life: Galls

Summer in the Northwoods can feel like a painting—broad sweeps of green and blue provide the backdrop for highlights in all colors of the rainbow. Winter, though, can feel like a pen and ink sketch, where shapes, textures, and patterns rule. I enjoy these shifts in perspective, since they can help me spot new things.

A little while ago I found myself in a weedy strip of vegetation between my friend’s driveway and a field. The colors of summer had all but drained from the thicket of goldenrod plants. Where once there were sunny yellow flowers tossing above a sea of green leaves, there now stood a sepia-toned jumble of fuzzy seed heads, crinkled leaves, and leaning stems. In this winterized sketch, I scanned the lines, looking for a particular pattern.

Goldenrod galls are small, round lumps that appear near the tops of the growing stems in response to the chewing action of insect larvae. Every year I collect a couple gallon bags full of these galls to use in our MuseumMobile lessons. With kitchen shears in-hand, I had soon accomplished my goal.

Many of the galls were the typical, spherical homes of goldenrod gall fly larvae. But as I started sorting through and cutting them open, I found one that didn’t match. It wasn’t much different—only slightly taller than wide, with some raised ridges. I knew that its real differences were hidden inside. A sharp knife around the equator of the gall soon revealed a hollow center with a shiny brown shell rattling around. The shell was the dried out puparium (like a chrysalis) of the goldenrod gall moth—Gnorimoschema gallaesolidaginis—whose larva created this elliptical gall.

An elliptical gall formed by a gall moth on a goldenrod plant. Photo by Emily Stone.

As I rolled the thin, mummy-like shell in my fingers, it cracked open. The split did not reveal a metamorphosing moth pupa changing from larva to adult. Instead, dozens of tiny, white, translucent larvae—each only about 2 mm long—spilled out of the hollow cylinder. Any normal person would have been grossed out. I was thrilled! The moth larvae are parasites on goldenrod, and they themselves are victims of many different parasites. I wrote about this in 2017, when all I found was a hollow, hole-riddled shell, cleaned out by the larvae of a tiny wasp.

The shiny shell of a gall moth puparium—only 2 mm in diameter—cracked open to reveal a mess of tiny parasitic wasp larvae that ate their host. Photo by Emily Stone.

Based on some research and inquiries, these translucent larvae probably belong to a different species of tiny, parasitic wasp. While wasps like these can’t sting us—their ovipositors are just for depositing eggs—they do play an enormous, and largely hidden, role in our ecosystems by keeping the populations of other insects in check.

I currently have some of the larvae tucked away in a Mason jar with a damp paper towel in the hope that they will metamorphose into adults and give us more clues as to their identity.

In the meantime, I found another curious pattern in the lines of my winter woods.

On several snowshoe hikes recently, I’ve gazed up at the lace of bare branches silhouetted against the sky, and found one tree among them covered in lumps. While these woody balls persist through the summer, they are out of sight and out of mind—hidden by that wash of green.

Like the lumps on goldenrod stems, I figured that these were probably galls. Plant galls are simply abnormal outgrowths triggered by everything from viruses, fungi, bacteria, insects, and mites, to other plants. Which of those parasites could trigger such persistent, woody galls?

Rounded galls caused by a fungus dot the branches of a northern red oak tree. Although a red maple’s twigs are intertwined, it does not seem to be infected with the fungal parasite. Photo by Emily Stone.

The answer, according to a fact sheet from the Wisconsin DNR, is that these galls are caused by a fungus in the genus Phomopsis. While little is known about how the fungus spreads, it seems to start on the smallest twigs before moving to larger branches. Often, only a single tree or a small cluster will be impacted. Some twigs or branches may be girdled and die, but the main tree will survive for many years. There is no treatment available, or even needed, although you can cut off infected branches if you find them unsightly. I find them whimsical!

While I’ve mostly noticed Phomopsis galls on northern red oaks, they also occur on maples, hickories, and other species in Wisconsin. Around the world, the fungus causes galls on trees in Italy, Poland, Spain, Portugal, Switzerland, England, India, Russia, Tunisia, and more. (This list is gleaned from the titles of scientific journal articles written about the fungus, but could also serve as my post-pandemic travel goals.)

The austere sketch of winter reveals many patterns. We see lines…and lumps where lines should be. We see the patterns of lives interwoven.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.

Thursday, February 4, 2021

Like a Rifle to my Dreams

I opened my garage door and gazed out toward the setting sun over an expanse of snow-covered ice. Strange, I thought. The lake level must have risen, since the ice was now level with the sill. Turning to the right, my heart jumped when I saw two young polar bears playing in the snow just meters away. They were white, fluffy, and cute. Although their body shape was wrong. Maybe they were albino black bears? In any case, they paid me no mind, and seemed to present no danger. But, where was their mother? Then CRACK! A sound like a rifle shot reverberated through the air.

I awoke with a start and opened my eyes to the dark room. The bears had been in my dream (where did that come from!?), but the sound was from real life. I fumbled through a sleepy haze to understand the noise. Was the house falling apart? No, there were no other sounds of destruction or chaos. Then, obviously, it must have been a tree cracking open in the cold.

I checked my phone: 3:30 a.m. I opened my weather app and checked the temperature: -13 degrees Fahrenheit and falling. Outside, a full moon cast shadows in the brittle cold. “Sweet,” I thought to myself as I rolled over, “now I know what to write about this week.”

The thermometer read -18 degrees when I came downstairs to make coffee. This had been one of the coldest nights of the winter so far, and it followed on the heels of a really lovely, clear, sunny afternoon. At one point I had turned my face to the sun and reveled in the warmth I felt—even though the high temperature only reached 11 degrees above zero.

My face wasn’t the only thing absorbing warmth. The low-angled rays of afternoon sun were beaming their energy onto the southwest sides of trees. This heats up the bark and the inner wood. When things warm, they expand.

The other side to that, of course, is that as the Earth’s heat escaped into a cloudless night and temperatures plummeted, the wood contracts rapidly and unevenly, with the outer layers showing the most dramatic change. The contrast is divisive, and the sound of wood ripping apart is loud.

Even as it burst into my dreams, the past night’s crack had sounded close. So, once the temperature rose above zero, I layered up and decided—without much hope—to see if I could find the tree who split. Standing under my bedroom window, I turned to look northeast—at the southwest sides of the trees—the side that usually cracks. Sure enough, there were at least a half a dozen narrow scars snaking lengthwise up trunks. On ashes, maples, and hemlocks, these cracks had all been trying to heal themselves for years if not decades. These were good evidence of past frost cracking.

On snowshoes, I took a little tour of the scars. They were filled with rough bark, old mushrooms, beetle-hole-riddled wood, piles of sawdusty larval frass, crusty specks of wound-healing pitch, and the messy webs of now-frozen spiders. Wonderful stuff, really. These old tree scars are fun to explore!

The scar from an old frost crack.

Old mushrooms

Beetle larvae frass (poop) that is basically sawdust.

Spider webs

Want to learn more about these and other Unsung Heroes of Nature? I'm giving a talk on February 11, 2021, for the Master Gardeners, and everyone is welcome! 
Find more info and the registration link here.

As I came full circle, though, the black stripe of a narrower crack caught my eye. It was on the southwest side of a young basswood tree—less than a foot in diameter—and just beyond my bedroom wall. Close up, I found none of the scar tissues or evidence of age I’d seen in the other scars. Instead, I found the warm brown colors of bark that hasn’t been weathered. I found small slivers of creamy wood—freshly exposed. And I found a deep crevasse filled with glittering crystals of hoar frost—assembled from moisture recently released from damp wood.

Some previous injury weakened this young basswood tree, and then plummeting temperatures caused it to crack open with a sound like a rifle shot. Photo by Emily Stone. 

Freshly exposed wood and hoar frost in this crack give clues to just how recently the fissure opened. Photo by Emily Stone.

When this frost crack opened, humid air inside the wood made contact with frigid temps, and hoar frost crystals grew. Photo by Emily Stone.

Freshly exposed wood and hoar frost in this crack give clues to just how recently the fissure opened. Photo by Emily Stone.

Radial cracks like this one—fissures that dive inward to the tree’s core instead of just separating inner bark from outer bark—are associated with injuries sustained in the tree’s youth. Did some piece of equipment scrape against this young basswood 20 years ago as the house was being built? The injury creates an area of weakness, and an entry for decay. Bacteria and fungi move in, and as they decompose the wood it absorbs extra moisture. The defective wood doesn’t expand and contract as well as healthy wood, and rapid freezing finally bursts open a significant crack. CRACK!

Warm weather will allow the wood to relax and close the crack again. The tree will begin to build scar tissue around the injury. And maybe, with quieter nights, I’ll get to enjoy the antics of those polar bear cubs.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at Or order it from our friends at to receive free shipping!

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is closed, but our Mysteries of the Night exhibit is available online. Connect with us on Facebook, Instagram, YouTube, and to keep track of our latest adventures in learning.