Thursday, May 19, 2022

Growing Up WILD: Dragonflies

“Welcome to Perry Lake and your Growing Up WILD field trip,” I smiled at a small group of kids and adults on our first field trip of the spring.

“Lakes are cradles for all sorts of babies as they grow up,” I told the group. “How many of you like to play in the mud and water as you grow up wild?” The little ones—only 3 and 4 years old, grinned. One student looked up at his teacher. “I love mud best!” I chuckled in agreement.

Then we all transformed ourselves into dragonfly eggs by hugging our knees. We wiggled, and grew, and hatched into crooked-legged-nymphs. Then our job was to eat. “What do you like to eat to help you grow?” I asked each kid. The answers included noodles, spaghetti, mac and cheese...do you notice a trend here? “Well dragonfly nymphs eat snails and minnows,” I declared. “How would you like that?” Their faces scrunched up just as I’d expected.

“Then, when we’ve eaten enough, we POP into dragonflies and zoom around and eat mosquitoes!” The chaperones cheered at that.

Our next task was trying to catch some actual dragonfly nymphs in the vegetation at the edge of the lake. I demonstrated proper pond net protocol, capturing a few dead leaves, and then turning the net inside out into my big, flat tub of water. Staring intently, I checked for any sign of success. When two demo swishes of my net turned up no sign of life, I got a little worried. Ice only went out a week ago, were the critters still hiding elsewhere?

Still, I handed out nets to the kids, and they ventured off along the shore to try their own luck, each with an adult or two in tow. Of course, someone started on the dock—and was soon shouting about a minnow! The tiny fish—only about an inch long—was striped with dark parr marks. This helps them camouflage into the tall, thin weeds.





I stood sentry at the tub to help kids empty nets and catalogue their catch. Out of the corner of my eye, I noticed that the adults were visiting the bin of extra nets. Within a few minutes, everyone was on a mission to catch more critters. A chaperone later told me that the adults got competitive about who could net the coolest finds. There’s no age limit to being a kid on my field trips!

Soon our tub was home to a giant tadpole—just its bulbous head was an inch long, and the tail added another two—and a tiny turtle. Actually, they were the same size. The difference, of course, is that the tadpole already had legs and was about as big as they get before becoming a frog. In contrast, the turtle must have just hatched last fall, and was about as small as you’ll ever find them!

Finally, I spotted a tiny monster among the leaves just deposited from an adult’s net. “Gold star for the day!” I exclaimed! She had found the dragonfly nymph we’d just been imagining.

This little aquatic monster is a dragonfly in the middle of childhood. Just like human kids, they grow up wild! Photo by Emily Stone.



The nymph stage of a dragonfly’s life is essentially their childhood. After hatching from a tiny egg, they shed their exoskeleton several times as they grow. Dragonfly nymphs may spend anywhere from several weeks to several years growing through the instars. The cooler and shorter the summers are where they live, the longer it takes to emerge as an adult. In the meantime, they rule the bottoms of lakes and rivers as fierce predators.

To catch food, a nymph draws in water through their anus, and clenches their abdominal and thoracic muscles against the water-filled rectal chamber. The amazing amount of pressure now trapped inside the nymph’s body cavity pushes out their labium, or toothy lower lip, in a high-speed strike. The lightning attack may earn the tiny predator a meal of tasty mosquito larvae, a tadpole, a small fish, or even another species of dragonfly nymph.

The dragonfly nymph’s hydraulic system isn’t just used for hunting. By jetting water out the way it came in, nymphs can propel themselves forward at a speed of 10 centimeters per second. That power of acceleration can help when they are on the hunt, and also allows for quick exits if they become the hunted. As the water goes in and out, it passes by gills in the dragonfly’s rectum, and helps the little critter absorb oxygen.

If they survive the winter, dragonfly nymphs will use the abundance of spring and summer to continue growing through their required eight to seventeen instars (depending on the species) before their final metamorphosis into adulthood. The process is astounding. From a split down the back of a scraggly, brown, bottom-feeder emerges a colorful, fairy-like being with delicate, dexterous wings.

There are many different ways to be a kid in nature. Some eat pasta, others eat snails. Some live in the mud, others just play in it. Some shed their exoskeleton as they get bigger, others buy new clothes. No matter whose kids I’m observing, though, it’s fun to watch them grow up wild!



Author’s note: Portions of this article are reprinted from 2014.


Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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 now open with our exciting Growing Up WILD exhibit. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Thursday, May 12, 2022

Robins and Hermit Thrushes: Cousins in the Woods

The hemlock forest was cool and dim as afternoon faded to evening. I hiked quickly, but with eyes and ears open, hoping to catch a whiff of spring. A flutter of movement caught my eye. Pausing, then creeping forward to see around a trunk, I was rewarded by a glimpse of the plump brown body and rusty tail of a hermit thrush. Silently, they made a series of short flights into the balsam thicket and vanished.


Hermit thrushes are one of the most melodious members of the thrush family.
Photo by Matt MacGillivray.



I smiled at the discovery that this early spring migrator had returned. And then, I listened even more carefully, hoping to hear the bird’s delicate, flute-like song filter through the trees as I have on so many gray-lit walks. “Whyyyy don’t you come to me, to me?” sings the lovelorn bird as the air begins to shimmer with magic. “Such soft and solemn and perfect music doesn't last for more than a few moments,” wrote Mary Oliver.

And from Henry David Thoreau:

“The thrush alone declares the immortal wealth and vigor that is in the forest. Here is a bird in whose strain the story is told…Whenever a man hears it he is young, and Nature is in her spring; whenever he hears it, it is a new world and a free country, and the gates of heaven are not shut against him.”

But my wish was not granted. Silence reigned.

The following morning, as the first light of dawn and my consciousness expanded in tandem, the incessant voice of a robin pierced through my closed window. Cheer up! Cheerily! Cheer UP! CheeriLY! Over and over he shouted a greeting to the Sun, an invitation to the lady robins, and a challenge to his foes.

Since the robin’s hedonistic exuberance left no moment in which to anticipate his next phrase, I rolled over with a grumble. He was no hermit thrush.

It’s hard, sometimes, to remember that these two birds are related.

The thrush family, Turdidae, includes a few obvious members, like the hermit, Swainson’s and wood thrushes. But there are also a few who are not so aptly named—American robins, veerys, and bluebirds. Of these, only the American robin is a “true” thrush in the genus Turdus.

Now, in case that made you giggle like a middle schooler…and because you know how much I enjoy teaching about scat in nature...I looked up the etymology of both words. Unfortunately, turdus is simply Latin for “thrush,” while turd seems to have its origins in old words that mean “torn off” and also shares some very old roots with the word scat.

Moving on, I think it’s useful to remember the things that robins and hermit thrushes have in common. Both birds are prolific singers, and you’re welcome to disagree with me about the hermit thrush’s song being more pleasant. Both birds have plump bodies in shades of brown and orange. They walk about with upright postures, and they often forage on the ground.

Robins, classically, run across the grass and then stop to search for worms. It may look like they are listening, with their head cocked to the side like we would, but sight seems to be more important. They find worms by spotting the disturbances they make in the soil. Observations have shown that they focus on earthworms for breakfast—presumably when the moist-skinned invertebrates are most active—and then switch to fruit later in the day. Sometimes they do double duty by selectively eating fruits that are infested with insects. Clever!

While I’ve seen plenty of robins in the wilderness, hermit thrushes are rarely seen on lawns. Hermit thrushes have their own fascinating foraging techniques for forest glades. They sometimes hunt by “foot quivering,” where they use their feet to shake the grass and scare up insects and other small critters. One hermit thrush was observed trying to use a 1.5-inch-long salamander as baby food!

Both of these birds, and all the thrushes, build cup-shaped nests that often include mud. Robins build their nest on a horizontal surface. Branches or doorframes seem to work equally well, unless it’s your front door, of course. Hermit thrushes build their nests on the ground. Bluebirds are the odd duck of the thrush family—they are the only cavity nesters of the group.

American robins, like most members of the thrush family, make cup-shaped nests that often include mud. Photo by Emily Stone.



The robin woke me up again today. He’ll likely be my alarm clock for the rest of the summer as he rushes to raise up to three broods of chicks. Hermit thrushes will soon join the chorus, too. Hopefully, as Thoreau predicted, “whenever he [or she] hears it, it is a new world and a free country.”




And now, some more bonus artwork from my young friend!

Hermit Thrush by Annaliese Collins



American Robin by Annaliese Collins




Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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 now open with our exciting Growing Up WILD exhibit. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Friday, May 6, 2022

Curious Cottontails

My typing grew halting, then paused. I gazed out of my office window, trying to figure out how to begin my next Natural Connections article. To my surprise, I had more than just mottled green lawn to look at—a fuzzy brown bunny sat nibbling on the blades!


Eastern Cottontail, by Annaliese Collins


As I watched, their little mouth worked back and forth on the patch of grass, and their ears twitched this way and that, listening to the sides and behind—then abruptly rotated forward with cartoonish focus when a burst of laughter in the office filtered out through the glass. Was the giggling something for the bunny worry about?




A cottontail can rotate their ears three-quarters of the way around, like little satellite dishes picking up any signals that could mean danger and assessing their location. I could see the anxiety in their quivering muscles.

It’s appropriate for the bunny to be on high alert—almost every predator eats them! The long list includes foxes, coyotes, wolves, and domestic dogs; bobcats, lynx, several types of weasels, raccoons, and snakes. Birds of prey might be their biggest threat, though. In some places, they are the primary lunch of red-tailed hawks. In other regions, great-horned owls are their main foe.

Big metal predators do a number on the population of bunnies, too. A study in Missouri found that ten eastern cottontails are killed annually per mile of road, mostly in spring when the ditches green up before the fields. Disease kills another 18 percent. All told, only 20 percent of adult rabbits survive each year, and the mortality rate of babies is even higher. The average bunny only lives to their fifteenth birthday—15 months, that is.

It's lucky then, that cottontail rabbits breed like, well, rabbits.

Rabbits reach reproductive maturity at three or four months of age, which makes their average lifespan seem a little more reasonable. Most females don’t breed until the spring following their own birth, but a few get started popping them out in their first summer.

Since cottontails can be found all the way from southern Canada to northern Colombia, their breeding season varies quite a bit in length—along with the number of litters a female can have in a year. In Wisconsin, three litters is about max, but in some areas they can manage up to seven litters of up to twelve kits each! One literature review published by the Colorado Division of Game, Fish, and Parks found that some females produced up to 35 kits per year.

How is that even possible!?

First, gestation takes less than a month. Second, the doe (female rabbit) mates again soon after she gives birth. Just as her first litter is weaned at about 22 days old, her second litter is on its way.

I’m exhausted even typing that.

Of course, cottontails don’t do very much active mothering. Nests are only 5 inches deep and consist of a scratched-out depression in a clump of grass or under a bush. While the babies are born blind and with hardly any hair, the female does not stay in the nest with them, instead she returns just once or twice a day to feed them. In contrast, my friend’s 3-month-old baby is eating every 2 hours.

The adaptation that makes this extended feeding schedule possible is that cottontail milk is about 14 percent protein and 35 percent fat. Rich milk is common among animals who leave their young alone for long periods. In comparison, whole milk has 3.5 percent fat, and human milk contains 4 percent fat.

Baby bunnies need nutritious food to grow up fast and make more bunnies before they become another animal’s baby food!

The rabbit must have darted off while I was googling them, but soon another movement caught my eye. The brown bunny had reappeared among the dry leaves and stems of our pollinator gardens, which had been left alone through the winter to protect overwintering insects.

I grabbed my camera and zoomed in, captivated by a shiny black eye, those alert ears, and an impressively active nose. Twitching their nose up to 120 times per minute exposes a rabbit’s 100 million scent receptors to the smells of danger.





Plus, they look adorable doing it.

700 words later, just look at how productive staring out the window can be!


Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.



And now, a bonus story:

"When are you publishing a new book? Annaliese wants to illustrate again." I chuckled when this note popped into my message app the other night, especially when the writer admitted that she was Annaliese herself--having commandeered her mom's Facebook account.

Annaliese is the daughter of my first best friend, and Annaliese, at age 6, drew this swan to help illustrate my first Natural Connections book:


 


I replied to Annaliese, "No new books in the works, but you can illustrate my next article about bunnies!" And, this is the result:




Eastern Cottontail, by Annaliese Collins


She's done quite a lot of growing as an artist!

Six years after the swan, Annaliese is a vibrant, energetic, Girl Scout, dancer, volleyball player, and artist. As I've watched her grow up through her mom's social media posts, I find myself thinking that she looks like someone I'd like to be friends with...even if she wasn't also the spitting image of my first best friend!

I hope you enjoy seeing her artwork as much as I do!


Thursday, April 28, 2022

Prairie Fire

Flames crackled at my feet and the sunset clouds reflected a little of their orange glow. The heat on my face contrasted with cold water on my back as I held the nozzle of a backpack sprayer at the ready. Glancing downhill, I could just see my dad’s head above the smoke and flames as he walked the fire line with a drip torch, a magic wand of destruction.

As luck would have it, I’d arrived home just as the weather had given us the perfect evening for burning prairie.


The mowed path of sledding hill below my childhood home doubles as a fire line. The flames of this backfire are sandwiched between short green grass and the prevailing winds, so they are less likely to get out of control. Photo by Emily Stone.



The house where I grew up in Northeast Iowa sits on top of a hill that was once planted to corn. When my parents bought the land in the late 1970s, they started planting native species even before they drew up plans or built the house. Each fall, Dad mows paths through the big bluestem for sledding and skiing, and each spring, those paths turn into fire lines for a prairie burn. It’s been years since my timing has been right to help.

Driving around the Midwest, I often squint at the fields of corn and beans and try to imagine the waving oceans of prairie grass that once were. While Iowa sits at the edge of the rain shadow of the Rocky Mountains, it’s not lack of rainfall that kept the land in grass instead of trees; it was fire.

My dad wasn’t walking the trails with a drip torch back then, so how did early prairie fires ignite?

In a study just published last October, a group of researchers in Illinois combed through records of prairie fires between 1673 and 1905 in an area that spanned from North Dakota to Ohio, and included Wisconsin. They found evidence of 795 fires in newspapers, diaries, explorers’ journals, and other historical documents. Of those, only five were started by lightning. Native Americans—already being pushed off their land—only set 32 of the fires. The rest were ignited by Europeans, either accidentally, or because they’d learned from the Native Americans how useful fire could be.

For many reasons, the practice of burning prairie diminished. Today, though, wherever people are trying to restore or reconstruct native prairies, fire is recognized as an invaluable tool.

While my yard in Wisconsin is still mostly covered in snow, lawns and weeds had both begun to green up in Iowa. Woody shrubs were beginning to swell their buds, too. Burning in mid-spring maximizes the impact of the burn because the fire will knock weeds back and force them to struggle.

In contrast, prairie grasses and flowers are mostly “warm season” plants who haven’t begun growing. Fire clears out the thick thatch that can smother new sprouts. Black ashes absorb sunshine, warm the soil, and provide prairie plants with an extra boost. Fire is a form of decomposer, and makes nutrients from dead vegetation available for new growth.

While most land managers advocate for burning prairies only every few years, my parents burn around the house on an annual basis. Their hope is that regular burning prevents the buildup of fuel and reduces the danger from an unplanned fire. They also hope—with some science to back them up—that burning around the house will reduce their chances of getting Lyme or one of the many other tick-borne diseases that seem to become more common each year.

As a campfire-poking kid, I love the idea that setting fires has a scientific and ecological purpose. But burning prairie safely requires skill and planning. Mom and Dad have their system down so well that they often manage all by themselves, although they were grateful that I offered to carry the heavy water pack, and my partner was there to rake vigorously at the fire lines.

Long before Dad set a match to the drip torch, we’d waited for the gusty winds to die down, hosed down the sledding run on the east side of the hill, wet down the strip of lawn near the house, watered the few shade trees, raked around the bluebird house, and cleared a space around the electrical box. Dad even put a barrel over a tiny seedling oak—supposedly descended from Aldo Leopold’s “Good Oak.” Hoses, jugs, and rubber flappers all stood at the ready to put out stray sparks.

The first fire Dad set was a backfire—sandwiched between the mowed path and the westerly winds—and it crept along slowly, using up the fuel. When Dad’s slow, glowing walk finally reached the bottom of the hill, and then the windward edge, we had enough guardrails in place that I could laugh with glee as flames whooshed up the hill. Sparks danced skyward toward a full moon as darkness descended.

Drew Guttormson watches over a prairie fire in NE Iowa as a full moon rises in the background. Doing controlled burning around the house helps to reduce the danger from unplanned fires, and even reduces exposure to tick-borne diseases. Photo by Emily Stone.



By the time we were done, there was no wind left to fan new flames and evening humidity was curtailing the rest. Deep below the blackened soil, a web of roots, burrows, insects and more bided their time.

When the Sun rose on the scene, the pair of bluebirds was already foraging in the ash. Rain in the forecast would bring with it a flush of new growth. The fire’s destruction would soon become renewal.




Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.




Thursday, April 21, 2022

Turkey Vultures

The silhouettes of turkey vultures soaring above farm fields and highways kept me company recently on a long drive to Iowa. With snow still falling at home, these drab, brownish-black scavengers gave me hope that a new season is on its way—however haltingly.


Photo By Charles J. Sharp - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=47807279



Most people probably don’t associate turkey vultures with spring—or even realize that vultures may have flown as far as South America for the winter—but they are one of the earliest returning migrants. “What blazes the trail,” wrote Mary Oliver, “is not necessarily pretty.” Vultures need warm weather so that the smell of their food can rise skyward, and because it’s far easier to eat fresh roadkill than frozen dinners.

Just a few days after I arrived home again, I caught sight of the V-shaped wings and rocking, unsteady flight of a turkey vulture soaring above my road. I suppose the “buzzard” was trying to wait until temperatures increased enough for warm-air thermals to buoy up their gray-fingered wings.

Having thermals to lift the birds upward so that they can coast onward is far more essential to a turkey vulture’s migration than a tailwind. It’s so important to find thermals, in fact, that turkey vultures congregate in big migratory flocks that find invisible air currents. Since migrating in a big group means that there will never be enough food to go around, it’s a good thing that using thermals also significantly reduces the metabolic energy necessary for them to fly.

For as long as I can remember, Dad has been pointing out every turkey vulture (TVs he called them) soaring over every road trip we ever took. And it was fun, even as a kid, to be able to easily identify such a large bird flying so high up in the sky. They have an excellent gross-factor, too, which kids love. “Don’t get to close to a turkey vulture,” warned the park ranger on my first grade field trip to Effigy Mounds National Monument, “they’ll throw up all over you!” That I still clearly remember this fact, and the moment I learned it, validates my own love of using yucky facts to teach kids.

Since that day, I’ve discovered many more wonderfully revolting facts about turkey vultures.


First of all, projectile vomiting is a defense they use against predators, not just curious humans. The foul-smelling mix of semi-digested meat and digestive fluids can sting if it reaches the predator’s eyes. In addition, emptying their stomach may be necessary to lighten the load for take-off and escape if a TV is interrupted while gorging on a roadside carcass.

Turkey vultures don’t just spray gross stuff on enemies; they also defecate on their own legs. This habit has a scientific name (urohidrosis) and a valid purpose. As water evaporates from the combination of urine and feces (birds don’t separate their waste like we do) it cools the blood vessels in their legs and feet. The acidic liquid may also act as a disinfectant.

Even though they can’t sweat, vultures’ feathers sometimes become damp during dewy, foggy, or rainy nights. Then, while they wait for the air to warm enough to begin rising in thermals, TVs perch in a spread-winged stance in the sunshine. This not only dries feathers, but it warms their body, and bakes the bacteria off their feathers and bare, featherless head.

In addition to antibacterial behaviors, turkey vultures have developed excellent immune systems that can ward off and even destroy the microbes that cause botulism, anthrax, cholera, and salmonella. Their stomachs, gross as they may seem, help purify our world. Can you imagine a world in which dead things all rotted slowly in place? Turkey vultures embody the fact that “the secret name of every death is life again.” (Mary Oliver, Skunk Cabbage)

Despite their gross appearance, every adaptation of the turkey vulture seems aimed at cleanliness. How appropriate that the TVs’ scientific name—Cathartes aura—means “purifying breeze.”

The story of the vultures—of winter’s rotting wounds transformed and purified, of the purifier rising up into the sky, of it returning to cleanse the world again and again—sounds a lot like another story I often hear this time of year.

“Like large dark lazy butterflies they sweep over the glades looking for death, to eat it, to make it vanish, to make of it the miracle: resurrection...” from Vultures by Mary Oliver.


Author’s Note” Portions of this article are reprinted from a 2014 Natural Connections article.



Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Thursday, April 14, 2022

Spring Reminders: Pollinators and Oak Wilt

All across the internet I’m seeing photos of green grass with pollinator-friendly people warning “leaves the leaves!” and “don’t clean up your gardens yet!” I chuckle jealously at those posts while watching another few inches of heavy wet snow come down. Here in the Northwoods, we’re dreaming about spring alright, but we’ve got a few more weeks of mud season to endure first.

In the case of the leaves and gardens, the issue is the bees, butterflies, fireflies, and other beneficial insects who have snuggled down in the duff or holed up in hollow flower stems for the winter. They aren’t eager to come out of their warm hiding spots until they’re sure it’s going to be sunny and warm. So, cleaning up your flower gardens—especially if you have lots of perennial native species you planted with pollinators in mind—will need to wait until tomato-planting weather. That way you know that the days and evenings are consistently warm enough for the insects to have emerged.

Warm weather also warns us that a not-so-beneficial insect may have emerged already.

Sap beetles in the family Nitidulidae are one of the main vectors for oak wilt. Oak wilt is a fungal pathogen that kills trees in a single season. While it’s already widespread in southern Wisconsin, it only arrived here in the north in 2018.

When an oak tree is injured—by a bulldozer, trail groomer, windstorm, pruning cut, logging, etc.—sweet juices begin oozing from its wounds, and that scent lures in hungry beetles. If those beetles have already been eating from a tree infected by the oak wilt fungus, they will transport spores and inoculate a new infection.

These beetles begin flying around as early as April and continue through July. They can’t chew their own holes, but any sort of wound can be the entry point for oak wilt into your forest, and your neighbor’s forest, too. That’s why this reminder is an early spring tradition—if you need to do some work in your yard, do it now while we’re still in “third winter”…or wait until fall.

In order to curb the spread of the fungus, land managers must cut all the potentially affected oaks and quarantine the wood under a tarp for a year so that beetles can’t spread the fungal spores. That can take up a lot of space.

This winter, Paul Cigan, a forest health specialist with the Wisconsin Department of Natural Resources (WDNR), teamed up with Max Wolter, a fisheries biologist with the WDNR, to dispose of oak-wilt-infected wood in a creative way. “So far, the DNR’s Hayward Fish Team has created a total of 16 fish cribs from oak wilt trees on Windigo, Little Sissabagama, and Placid (Tiger Cat Chain) Lakes,” reported Max. “The crew worked hard to construct some really impressive cribs that anglers may find in their next trip to one of these lakes.”

Foresters and Fisheries biologists from the Wisconsin Department of Natural Resources used oak wilt-infected wood to create fish cribs this winter. The cribs will create habitat while preventing the spread of pathogens.
Photo provided by the Wisconsin Dept. of Natural Resources.



Although this project started with the tragic loss of several oak trees, it ends with a win-win. “There is no link to oak wilt spread through water,” Paul reassured me. “The point of submersion is to get the wood (and its spore mats) away from beetles that like to visit them.” Additionally, since oak logs are solid and long-lasting, they will provide fish habitat for many years. Max would like me to remind you that installing cribs often requires a permit.

While those fish cribs—built on the ice—sink into the lakes over the next few weeks and take the oak wilt fungus with them, we have a job to do on dry land: keep an eye out for oaks with wilting leaves. When caught early by observant landowners and reported to your local WDNR office, infections can be contained.

Foresters from the counties, the WDNR, and the United States Forest Service are working together on their large-scale oak wilt detection and mitigation operations. Aerial surveys with planes and drones, and satellite imagery with computer analysis that can spot sick trees are at the forefront.

Oaks are a major component in our forests, and they are important ecologically, economically, and aesthetically. Preventing oak wilt will be a team effort.



Author’s Note: Portions of this article are reprinted from March 2020 Natural Connections.


Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books 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. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Thursday, April 7, 2022

Eastern Chipmunks: A Furry Sign of Spring

What are your favorite signs that spring is on its way? The first trill of a red-winged blackbird, the guttural cry of sandhill cranes, and the swelling of pussy willow buds are all on my list—foretelling of many more changes to come. But none of those have yet appeared at my house, which faces north and is surrounded by dense hemlock trees.

Spring may come slowly to my yard, but one of the first indicators is already scurrying around at breakneck speed.

Eastern chipmunks are early risers, at least in terms of the season. They’ve just emerged from their underground burrows—actually in the soil, not just the subnivean zone at the interface between soil and snow. Their cozy winter burrows, lined with dry leaves, can be two feet deep and up to thirty feet long, although I doubt we’ve measured enough of them to capture all of the variability out there.

While I was taught that chipmunks aren’t true hibernators, and spend the winter only taking naps and staying alert for hungry weasels, new research has refuted that idea. Craig Frank, Ph.D., associate professor of biology and a mammalian ecologist at Fordham University in New York, put radio telemetry collars that measure body temperature on wild chipmunks at the university’s field station.

Over the course of the winter, Frank discovered that chipmunks go through cycles of hibernation when their body temperature drops from 94 degrees to the ambient temperature of their burrow—around 40 degrees. During these periods of hibernation, their heartbeat slows from their normal rate (which is up to 350 beats per hyper, stress-filled minute) down to 4 beats per minute. From their typical rate of 60 breaths per minute, they drop to only 20.

Emerging from this intense nap is no easy task. But every few days the chipmunks warm up, wake up, feed on stored food, urinate, and defecate. It seems that these feeding sessions are necessary because chipmunks can’t put on enough fat to last them through the winter.

Chipmunks’ northern cousins, Arctic ground squirrels, are deeper hibernators. Their body temperature may drop to as low as 27 degrees. Even they warm up every few weeks, though. Unlike chipmunks, they don’t use that time to eat, they use it to sleep. The hypothesis is that REM sleep is necessary to keep brains healthy, and deep cold doesn’t allow for that.

In the refrigerator of my yard, I never see chipmunks up and out in the middle of winter, but in warmer areas, these striped little squirrels often pop up on a mild day. While you might assume that being warmer and able to find food in the middle of winter is nice for the critters, it may actually lead to their demise. Frank found that after the warm winter of 2016, when few chipmunks at the field station bothered to enter hibernation, most of them died in their burrows. During normal, colder winters, 87% survived. This is likely because the energy it takes to be active cannot be fully replaced by the meager food supplies available in winter.

The hints of warmth we’re feeling now are right on schedule, though, and active chipmunks are a happy sign of spring. Males wake up first, with females following a couple weeks later. Within another week, females are in estrus and ready to mate with a number of their neighbors. This—and the two months when moms provide care to their litter of two to six young—are the only parts of the year that chipmunks are social.

For the rest of the year, chipmunks defend their small territories and food caches from each other quite vocally with chips and chucks, sometimes lasting 30 minutes. Females tend to give alarm trills more often than males. This could put them at risk from a predator, but it may also alert their relatives to the presence of danger. Since females tend to stay closer to their mother’s burrow when they disperse, they are likely related to their neighbors.

Chipmunks eat a lot of seeds—often stuffing their cheeks under our bird feeders and stealing away—but in spring there are more options on the buffet. The tiny, carbohydrate-rich tubers of trout lilies are a favorite treat, as are trillium flowers, and mushrooms. Insects, frogs, snakes, slugs, worms, painted turtles, and even the eggs and chicks of songbirds have been discovered on the chipmunk’s menu, but those animal proteins make up less than 20% of their diet.

Here in northern Wisconsin, the range of the eastern chipmunk overlaps with the least chipmunk. The smaller cousins are more likely to be spotted in open areas or rocky outcrops, but I’ve seen both kinds at the same campsite in the Boundary Waters. Size is one clue to their identify, as are the stripes—which fade out on the rump of the eastern chipmunk, but continue all the way to the base of the tail on the least chipmunk.

No matter how long their stripes, chipmunks are a welcome sign of spring.


Eastern chipmunks emerge from their winter burrows at the first sign of bare ground and warming temperatures. Photo by Emily Stone.


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

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