Making Tracks on a Snowshoe Field Trip

Awooooo! My best impression of a wolf howl rose over the crunching of snowshoes and little voices. Gesturing to the group of third graders from the Hayward Intermediate School, I invited them to howl back. The choir that responded sounded nothing like wolves, but it was music to my ears nonetheless. So was the expectant silence that followed, since these kids were wise to the fact that I’d howled to get their attention.

“We’re going to hike like a pack of wolves today,” I declared. “Do you know how wolves walk when they’re in deep snow?” I led this same snowshoe hike four times over the course of two days, and in each group there was one outdoorsy kid who knew. Wolves walk in a single file line and step precisely in the footprints of the wolf in front of them. The kids understood the benefits of the wolves’ behavior intuitively. Who hasn’t made their own life easier by following in someone else’s footsteps through deep snow? 

“I’ve tracked wolves,” I told them, hoping to establish credibility. I’ve followed a trail that looked like it was made by just one wolf going through deep snow. When it came to a ski trail, though, the wolf tracks fanned out on the firm surface and I counted at least six in the pack.

With one last admonition to walk in a single file line, I howled again, and they howled back as we started up the trail.

The Mammal Tour on the Ridge Trail is a wonderful community resource. The 1.1-kilometer loop trail is the easiest of several snowshoe trails at the North End Trailhead just south of Cable, Wisconsin, and the Museum and our partners have created a self-guided interpretive trail along its length. We started out with plywood mammal silhouettes cut by the Drummond High School shop class, but hungry porcupines rendered most of those unrecognizable after just a few years.

This past fall, a funding drive spearheaded by the North End Ski Club and community member Ron Caple made it possible for us to commission a set of 25 new metal mammals cut by Mark Blaskey in Altoona, Wisconsin. We reprinted the booklets, too, which contain drawings, information, and tracks for all the mammals, plus a map of the trail. In January, attendance at our Backcountry Film Festival helped offset the cost of hosting this field trip.

I hiked the kids right past the shapes of a woodchuck, a big brown bat, and a chipmunk. When we finally stopped between the wolf and the deer silhouettes, I asked if they could guess why we skipped the other mammals. At least one student was paying attention. “You told us we were just talking about animals that stay active in the winter. Those animals don’t.” Haley Appleman, the Museum’s naturalist, was just then back in the Museum’s education room with the rest of their class talking about animals that migrate and hibernate. Out in the woods, we wanted to think about how animals confront the cold and snow head-on.

Wanting to wow them with the thickness of a wolf’s fur, I walked over to one of my helpers—a third grader carrying a heavy orange backpack. When I unzipped the pack and started pulling out a huge wolf pelt, a wave of surprised comments rippled outward. The helper was the most surprised of all. “You mean I was carrying that on my back!?”

Our next stop was below the form of a flying squirrel on the tree. Unlike wolves, they don’t have thick enough fur to sleep out in the open. For warmth, flying squirrels huddle together with their friends in a hollow tree. Handing out durable thermometers to small groups of kids, I challenged them to see how much heat they could generate by huddling together with their friends. Most groups brought the temperature up to 40 or 50 degrees, but one group of girls used their breath and registered over 70 degrees!

Down the trail, we compared the squirrel’s simple shelter to the more elaborately constructed lodge of a beaver. Even though we never see beavers in the snow, they are able to stay active all winter by snacking on their store of twigs under the ice and resting snugly in their lodge.

By far, though, my favorite topic to cover on any winter ecology hike is the subnivean zone. This magical space opens up at the boundary between still-warm earth and the insulating blanket of snow. Here, mice, chipmunks, voles, shrews, spiders, ticks, fungi and bacteria find their own special shelter.

As mysterious and invisible as this space is to us humans, however, a whole suite of predators have learned to access its rich stores of prey. Skinny weasels follow chipmunks into their burrows. Alert foxes and coyotes cock their ears toward scurrying mice and pounce through the snow. Vigilant owls’ precise hearing guides them to punch through the crust with bony talons and grab a late-night snack.

At our final stop on the trail, I invited the kids to explore the subnivean zone, too. In place of deadly accurate ears, I hand them mini-Frisbees I call “treasure finders.” Give it a toss, watch where it lands, then dig down. The Frisbee knows where treasures hide in the subnivean zone—which, of course, is everywhere. Every leaf, stick, acorn, or bit of moss is a treasure to some resident of this forest.

“Awoooo!” I called again, and “Awoooo-oo-oo!” my wolf pack replied as we began the last stretch of their hike back to the bus. With the end in sight, tired legs were forgotten and the group’s chatter turned to comments like “that was so fun,” “we hiked so far,” and “I wish we could go farther.” This, of course, was music to my ears.

Special Note: Columnist Emily Stone is publishing a second book of her Natural Connections articles as a fundraiser for youth programming at the Cable Natural History Museum. Since community members are often the inspiration for her articles, the Museum is conducting an art contest for kids and adults to illustrate each chapter with a black-and-white line drawing. Find the details and entry form at http://cablemuseum.org/connect/. 

Witches' Brooms and other Ski Trail Observations

This time of year, most of the nature I observe is along the cross-country ski trails in northwestern Wisconsin. Just a few days ago, I skied over a string of fresh red fox tracks. Occasionally a strong skunky odor accompanied them, and I looked a little closer to see which unfortunate pine seedling had been scent-marked. The tracks zig-zagged in and out of the woods, and eventually culminated in a fox-track party! This is the peak of their breeding season, so activity levels are high.

In among the fox tracks I started noticing foot prints from the fox’s largest cousin. Gray wolves are not uncommon here, and ski trails are some of their favorite highways. Wild animals enjoy easy travel as much as the rest of us because it helps conserve their hard-won energy. This particular gray wolf must have been eating well, because he also left a huge pile of scat right next to the ski tracks.

On a different ski, I spotted a tiny shrew frantically scurrying across the smooth snow of the skate-ski lane. When it reached the two parallel canyons of the classic tracks, an awkward scramble ensued to get itself up and over the humps. I chuckled at how different the world must look to each of us. Then, when it tunneled through the top skim of fluff just off the trail, I blinked in awe as it vanished. I’ve seen the results of this surface tunneling before, and always shook my head at how a little critter could think that nosing through just the top layer of flakes could hide it from the eyes of a watchful predator. I stood corrected…and alone…in the woods.

Sometimes I ski right past curiosities countless times before finally noticing them. That happened recently after I encountered friends on the trail who had a question. “What’s up with that big clump in a pine tree over by the second place the North End Trail crosses the Birkie Trail?” asked Irv and Jan Berlin. So I made a point to look up on my next loop out there, and then sent a photo to Paul Cigan, a Wisconsin DNR Forest Health Specialist, for his input.

“Cool find!” he replied. “I think I might have seen that very witches’ broom while out skiing.” Paul went on to explain that anything that kills a growing tip on a tree can instigate a thicket of new shoots that (if you use your imagination) looks like the business end of a broom. The name was coined in medieval Europe, and their homemade twig brooms bear an even stronger resemblance.

While anything from fungi to mites, mistletoe, bacterial parasites, and environmental insults can cause witches’ brooms, the most common initiator on pine trees, wrote Paul, is actually just a mutation of their own cells. An accident during cell division can result in an abnormal number of chromosomes in meristematic cells. Similar to a human stem cell, plant meristems are undifferentiated cells that can become a variety of different types of tissue. When dysfunctional meristem cells die, other shoots jump in to take their place. Or perhaps the meristems keep growing, but not in a normal way.

Because this witches’ broom is likely due to internal error and not a pathogen, it’s not at risk of infecting its neighbors. It might have a small negative impact on the tree itself, though, by sucking up nutrients that could be put to better use elsewhere in the tree. Paul speculated that “the one at the North End is moderately large and I would expect that it is reducing height, stem, and overall crown growth.”

On the other hand, some brooms have been observed to produce viable seeds that grow into dwarf trees. Humans have discovered that grafting a twig from a witches’ broom onto a normal rootstock can result in weird trees that collectors enjoy.

Sometimes, witches’ brooms can even play a positive role in the ecosystem. A type of moth uses the dense thicket to feed and shelter their larvae. Other critters, such as flying squirrels, might use them as a nest.

Fox tracks, wolf scat, mammal burrows, and witches’ brooms…what will I ski past next?

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: "Better Together--Celebrating a Natural Community" is now open!

The Great Migration of Miniscule Things

Time was running short. Dave Neuswanger, a retired fisheries biologist, had led such a fascinating discussion about winter limnology (limnology is the study of lakes), that the afternoon program of our Master Naturalist workshop was behind schedule. As we gathered boots, coats, and a digital meter that measures both temperature and dissolved oxygen, I suggested we bring the plankton net, too, and combine trips to the hole through the ice on Lake Namakagon. Dave hesitated, and gently reminded me why we hadn’t combined these data collection forays on the schedule in the first place: the critters we wanted to find just wouldn’t be near the surface in broad daylight!

Dave Neuswanger lowers the probe to test dissolved oxygen and temperature at 2-foot increments in Lake Namakagon while Master Naturalist students look on. 

Here are the results from our DO/Temp probe: Lake Namakagon has pretty hi dissolved oxygen almost all the way down to the bottom! That's a good sign for fish.

Many types of zooplankton (which are mostly microscopic animals in lakes and oceans) participate in a cycle where they swim up to the surface at dusk and descend to the dark depths again at dawn. Scientists call this diel vertical migration (DVM). The word diel comes from the Latin word for day, and refers to a 24-hour period.

Such a great number of tiny organisms exhibit this behavior that Professor Hays of Deakin University in Australia wrote “DVM in ocean zooplankton is likely to represent the largest daily migration of animals on Earth, in terms of biomass.” The DVM was discovered during World War II, when the U.S. Navy was using sonar to watch for enemy submarines. A dense group of zooplankton, moving in sync through the water column, scattered their sonar so much that it looked like a false bottom in the sea.

On our second, later, visit to the lake, I wasn’t sure what we’d find as Dave pulled our fine-mesh plankton net up out of the hole. We all cringed as he used bare hands to coil the net’s wet line. A pink sunset was just fading over the hills around Lake Namakagon when we trudged back to shore though soggy snow.

While the Master Naturalists munched on appetizers, Dave concentrated the sample and I set up the Museum’s new digital microscope. Just as we were getting antsy and students started to fill their plates with baked ravioli for dinner, Dave brought over a small porcelain cup filled with lake water. Careful not to spill, I set it under the microscope and fiddled with the focus wheels. Onto my computer monitor jumped a school of darting critters. Excited now, and wanting to share, I plugged the projector cord into my computer. A cheer of excitement rippled through the group as larger-than-life aliens scurried across the screen at the front of the room.

Almost all of the swimmers were daphnia. You may have seen these mini-crustaceans before, in a high school or college biology lab. Through their translucent carapace, it is easy to view the daphnia’s heart beating and blood cells flowing. They react quickly to alcohol and caffeine, so students can easily quantify the effects these substances have on a daphnia’s heart rate.

We didn’t want to torture these critters, though, just admire them. Roughly oval in shape, daphnia have a single large eye at the front of their body, along with two pairs of delicate, branched antennae. It is the second, larger pair of antennae that drives their movement, especially the sideways jerky hops that earn them the nickname “water fleas.” Despite their ability to move short distances, on a larger scale daphnia are at the mercy of strong currents, and tend to avoid them. Daphnia’s many legs are used to create their own, personal current that drives food through their carapace so they can filter feed.

This ability to convert bacteria, algae, and fine detritus into fish food makes daphnia an essential part of many aquatic food chains. (The mass exodus of zooplankton from surface waters during the day must be a huge boon to their phytoplankton prey who can then photosynthesize in relative safety.) Although any organism’s role in the ecosystem includes eating and being eaten, it’s also their evolutionary prerogative to maximize the first and delay the second. That’s where the diel vertical migration (DVM) comes in. Daphnia (and other zooplankton) are highly visible to fish in daylight, and sunrise triggers them to escape by fast downward swimming, not simply by sinking. Fast-swimming daphnia are more conspicuous, but for a shorter time, and escape the brightly lit, risky, upper waters faster.

Once they’re at depth, beyond the reach of sunlight, though, how would the daphnia know that dusk is falling? Scientists hypothesize that they use an internal clock, run by their single eye. Pigment in their eye changes over time, so their migration is synchronized by light at dawn and triggered by biology at dusk. While light is the main factor in their movements, DVM is expedited when the critters can smell fish nearby. The fish smell is a result of chemical substances called kairomones. This fancy word just means that what the fish give off is detected by a different species, who gains some sort of advantage from it. (In contrast, pheromones are detected by an animal of the same species.) In murky water, these chemicals may actually be a more important trigger of DVM than light.

Several Master Naturalists agreed that watching the daphnia swim under our microscope was better than TV. In the end, we were glad we’d gone back out at dusk to sample plankton, even though it delayed our dinner. Happy and exhausted from our long day of discovery, we participated in our own diel migration—going home to bed.

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: "Better Together--Celebrating a Natural Community" is now open!

Natural Connections in Costa Rica

I'm thrilled to announce that I'm hosting a trip to Costa Rica later this year!

Find out more, and download the brochure HERE!

Natural Connections in Costa Rica with Emily Stone

December 1 - 9, 2018 

On this 9-day expedition be prepared to experience the best of what Costa Rica has to offer. Spend time birding in the lush lowland forests of Sarapiquí and the highlands of Arenal Observatory. From guided nighttime and daytime hikes through the rainforest, to river rides in search of Costa Rica’s abundant biodiversity, to cultural interactions with locals, to learning about the work being done to conserve this beautiful land; this adventure-packed program is a journey you won’t want to miss. 

• Take guided hikes in the 500-acre primary and secondary rainforest reserve at Selva Verde Lodge, which provides habitat to more than 350 bird species, including the endangered Great Green Macaw. 
• Cruise by boat during a canal safari in Tortuguero amongst the reptiles, birds, monkeys and butterflies. 
• Learn about the history and production of chocolate and coffee on guided tours through the farms.
• Venture out on a whitewater rafting expedition down the Río Sarapiquí. 
• Experience a taste of life on the farm at Vida Campesina, and learn how to make homemade tortillas.

LAND PRICING $ 2,265 (10 participants) Cost includes meals, accommodations, and activities as indicated in the itinerary, in-country transportation, full-time guides, bottled water on the bus, carbon offset. Does not include international airfare, gratuities or items of a personal nature. 

Find out more, and download the brochure HERE!

Cecropia Moth Mummy

Laura Berlage had just impressed the students by showing them North StarHomestead Farm’s furry Kunekune pigs—a heritage breed from New Zealand that were made famous by their appearance in “The Hobbit.” Just beyond the barnyard we found another curiosity—and this one was a native!

I was looking for goldenrod galls, but what caught my eye was a cocoon attached to a maple stem near the trail. I tromped over in my snowshoes to get a better look. The students—part of an environmental psychology class from Luther College in Decorah, Iowa, looked on. (I think I had stunned them into silence earlier with my exuberance over finding weasel tracks by the wetland.)

The cocoon we found, in situ. 

Back in graduate school, I had the good fortune to spend a week studying winter ecology with author and ecologist Bernd Heinrich at his cabin in Maine. Between him and my tree-climbing friend Teage, our class collected and dissected over 20 cocoons belonging to Promethea moths. All of the pupae had been parasitized, mostly by ichneumon wasps.

Promethea moth cocoon. https://www.buglifecycle.com/?page_id=2373 

This cocoon didn’t quite look like I remembered, though. When the larva of a Promethea moth is ready to pupate, it finds a leaf and sews the stem more securely onto the twig so that the tree’s own system for being deciduous is overridden. Then the pupa wraps itself up in the leaf and spins a cocoon inside. This is reasonably good camouflage, but we (and probably other critters, too) found it very easy to recognize the “last-leaf-hanging” for what it was.

In contrast, the cocoon at the Homestead did not incorporate a leaf. (One was dangling nearby, but was not incorporated into the cocoon.) And, instead of attaching to the twig by a single point, the length of one entire side was glued firmly along the stem. Carefully, and with more effort than I expected, I peeled the cocoon off its twig. It felt crisp on the outside, with plenty of airspace, but I could also feel something solid and hefty in the middle.

After a mile-long loop along the fields and through the old sugar bush, we tromped in to the Farmstead Creamery and Café for lunch. Up in Laura’s new fiber loft, I pulled the cocoon out of my pocket and began to separate the layers. The outer shell was tough. Woven of gray-brown silk, it was paper-thin but fabric-strong.

Like Russian dolls, I found a smaller cocoon inside. It was dark brown and suspended within the outer shell by a network of fuzzy silk. This one, too, I tore open gently. Inside, the thumb-sized, black pupa looked like something you’d find in an Egyptian tomb. A pattern of ridges cloaked its head like King Tut’s famous headdress. It was firm, and seemed healthy and unparasitized. After exclaiming in excitement, I passed the pupa and cocoon around the table. As the pupa warmed up, one student noticed it wiggle just a tiny bit.

While I couldn’t put a name on this creature right then, it didn’t take long when I got Google involved. From photos, I surmised that this mummy-like pupa would someday become a cecropia moth. Author and insect expert Charley Eismen later confirmed this identification through the BugGuide.net website, explaining that: “Cecropia moths attach their cocoons to twigs along their whole length; the other species you mentioned do not.”

On a website devoted to raising cecropia moths from eggs, I discovered that you can tell from the shape of the pupa if the developing moth inside is male or female—and the King Tut-like headdress is the key! The moth’s antennae create the patterned ridges in the pupal case. Males have huge antennae, whereas the antennae of females are more modest. We’d found a girl.

Come spring (when I take it out of my refrigerator), this pupa will wake up and continue its development into an adult moth. Upon exiting the cocoon (through a silk pathway woven cleverly by the caterpillar), this beautiful brown-winged, orange-lined, and white-spotted female will begin wafting pheromones on the breeze. A male, with his giant, brush-like antennae, will sweep the air for her alluring scent and detect it from up to three miles away, even if is diluted to only a few molecules in the air. By flying upwind toward a higher concentration of pheromones, he’ll eventually find her. After they mate, she’ll lay about one hundred eggs. Not having a gut or working mouthparts, both adults will die within a few days to a couple weeks.

The caterpillars that hatch from those eggs start out looking tiny, black, and bristly, and end up being four inches long with lime green skin and a rainbow of bristles. They eat a variety of tree leaves. At the end of summer, a caterpillar will choose a stick and start to spin its cocoon. Outer shell first, then the inner, and finally the caterpillar sheds its exoskeleton to become the pupa. I found that exoskeleton in a crumpled ball inside the inner cocoon. The “face” of the caterpillar was still recognizable!

The double-wall construction of the cocoon doesn’t prevent the larva from feeling the freezing weather, but the barrier does insulate it from abrupt temperature fluctuations, as well as potential predators. Birds, squirrels, bats, and owls will eat the larvae and adults. Parasitic wasps may destroy the pupae. One of the biggest problems for cecropia moths, and many of their friends, though, is pesticide use and habitat loss. 

Hyalophora cecropia adult female taken by Shawn Hanrahan at the Texas A&M University Insect Collection in College Station, Texas.

Happily, the sustainable agriculture practiced on the North Star Homestead Farm allows for this and other natural neighbors to thrive. (and their sheep milk gelato is amazing!)

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: "Better Together--Celebrating a Natural Community" is now open!