Mouse Snacks

The light dusting of snow we received the other night was the perfect substrate for mouse tracks.  The morning light revealed a mouse freeway leading from the stack of flower pots to the mess of seed under the bird feeder. Their tiny tracks look like a smaller version of red squirrel tracks.  Mice and squirrels both hop by placing their smaller font feet down first, then bringing their larger hind feet around the sides.  As the hind feet hit the ground in front of the front feet, they give a mighty push for the next hop.  Rabbits also move in a similar way. 
 

You can decipher an interesting bit about the ecology of a hopping track-maker by the placement of their front feet. Arboreal animals, those who spend a lot of time in trees, will place their front feet right next to each other, perpendicular to their line of travel.  Squirrels do this, and a little surprisingly, deer mice are excellent tree climbers and therefore are sometimes paired-front-foot hoppers. Rabbits and hares, who are not often observed in trees, place their front feet with one ahead of the other, at an angle to the direction of travel.  Can you decipher all the tracks in your yard?

The appearance of deer mice – light brown back, white belly, and big ears – is reminiscent of a white-tailed deer.  Mice have much longer tails, though, which aids in their tree climbing.  Deer mice have a closely-related and almost indistinguishable cousin, the white-footed mouse.  To tell them apart, experts look at a difference in the amylase molecules of their saliva.  You might remember amylase from biology class when you chewed on crackers until they tasted sweet.  Amylase is an enzyme that breaks carbohydrates into simple sugars.

 

Food is especially important during the winter for these tiny active critters.  Mice will cache food (including weed seeds, birdseed, berries, and my cookie crumbs) in the fall, and throughout the winter.  Several times I have curiously brushed the snow off of an abandoned bird nest and discovered a tidy little mouse pantry.  Earlier this winter I accidentally left a Mason jar with birdseed in it on the patio.  I found it a few days later, with the contents spilled onto the snowy path.  Squirrel tracks, mouse tracks and tunnels surround the windfall as they busily hoarded the treat.

Eating plenty allows the mice to run their metabolism on full speed to keep warm.  In the winter they add new red blood cells with more hemoglobin to fuel their roaring metabolism. After creating all that heat, mice do their best to conserve it through the day when they are not active.  Body temperatures may be allowed to drop as they snuggle in next to other mice in a cozy woodpecker hole, thatched-grass nest, bluebird box, or the warm micro-climates of our homes.

Peering out of my home early one morning, I witnessed a bit of natural drama.  My local gray fox stood on the path by the corner, in person, not just in tracks! He was just ten feet away, standing over the remnants of spilled birdseed.  In the shadowy pre-dawn, I watched as he nuzzled the snow and came up with a limp mouse hanging from his jaws.  With a flick of his head, the mouse disappeared in one gulp. The fox trotted nonchalantly down the path leaving delicate tracks in the fresh dusting of snow.

In December, the fox tracks whispered “Listen…it is music to run over the hills” Now he adds: “Death itself is a music…It is flesh and bones changing shape and with good cause. Mercy is a little child beside such an invention.” (Straight Talk from Fox in Red Bird by Mary Oliver). 

 

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Love is in the Air

It's mid-February, near Valentine's Day, and love is in the air. Literally. Many animals are anticipating or are in the midst of their breeding seasons right now, and they are advertising it through air with sound and scent. You've probably heard a few eager chickadees singing their "hey sweetie" love songs despite below-zero temps. They won't breed until April, but it doesn't hurt to get a head start impressing the ladies, right?

If you have owls near your home you may be hearing their eerie calls more often. Great horned owls and barred owls both mate this time of year, and are calling back and forth to communicate both with potential mates and potential competitors. One of the great horned owls' prey species, the wild turkey, has also been noticed strutting to impress the ladies recently.

Wolves have already been thinking amorous thoughts for a month or so. You may have heard them howling along with the owls. Within a pack, typically only the top male and the top female (the alpha pair) mate. They will announce their intentions with a "paired RLU." This is where the male initiates raised leg urination (RLU) to leave a scent mark, and the female then urinates next to his. If the female is in estrus, you may see a few drops of blood on the snow.

Bobcats are typically a solitary species, but this time of year the males and females will strike a tentative truce for mating season. Males and females will increase their scent marking behavior, which may help them learn about potential mates, and find each other when the time is right.

Two of the bobcats' favorite prey species, gray squirrels and red squirrels, are also starting to feel amorous. You may have noticed that the squirrels have been extremely active recently. Their mating rituals begin with a chase, as up to ten males compete for one female. Their arboreal acrobatics can be quite entertaining. Male squirrels can smell when a female is in estrus and ready to mate. This is a useful skill, since she is only fertile for one day.

Often in mid-winter I will notice little splotches of red in the squirrel tracks around my bird feeder. I haven't been able to find any information relating directly to this, but my guess is that it's a sign that a female is in proestrus, and, just like the wolf, is leaking a little blood. As spring keeps peeking at us from around the corner, we will continue to see even more amorous behavior in the woods.

What are your plans for Valentine's Day? Perhaps you will consider wooing your date with a sweet song or a designer perfume!

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Ode to the Glaciers

What do you love most about Northern Wisconsin? Rolling hills traversed by some of the best trails in the country, winding back roads, sparkling lakes, and shady green forests are some of my favorite features. Have you ever wondered why all these wonderful things come together in Northern Wisconsin? Maybe you know that this region was shaped by glaciers, but have you ever really sat down and appreciated all that the glaciers did for us?

I love glaciers. I have never seen one in person, and yet they have vastly improved my quality of life. Whether you realize it or not, you also know the joys of glaciers whenever you whiz down a rolling ski trail, hike merrily up and down hills, enjoy the stomach-dropping exhilaration of catching air on your snowmobile, or boat and fish on one of Wisconsin’s more than 10,000 lakes.

The landscape around Cable and Hayward was shaped during the Wisconsin Glaciation (named for us!) of the Quaternary Ice Age (which is still going on in Greenland and Antarctica). It began about 100,000 years ago, hit its maximum extent about 21,000 years ago, and the last glacier had retreated out of Wisconsin into Canada by 10,000 years ago.

The very recent (geologically speaking) visit of a glacier here has had a profound impact on what the landscape looks like. As glaciers advanced across the land they scraped and carved and plucked up rocks from their path, and carried them along within the ice mass. Like a conveyor belt, they brought tons (literally) of sediment south with them. Two lobes of ice flowed into our area, and their lateral margins met somewhere near Cable.

Where we really start to get interested is when the climate warmed and the ice began to melt faster here at its toe than new snow from Canada could replenish it.  Huge chunks of ice were left behind from the melting edges of the glacier, and then glacial outwash rivers carrying meltwater and debris off the glacier buried those ice cubes.  Well-insulated, the ice lay hidden under a flat surface of sand, gravel and cobbles for many years.

As the ice melted, basins of all shapes and sizes were left behind where the ice had been. Sometimes these basins, called kettles, filled with water and became lakes, others are perched far above the water table and stay bone-dry. The landscape of sandy, rocky soil pockmarked by kettles is called a “pitted outwash plain.” The Rock Lake ski and mountain bike trails east of Cable are a prime example of this topography, and in my opinion, a prime place for recreation because of it. The Birkie Trail takes advantage of the varied topography so much that its hills are legendary.

In places, the glacial conveyor belt stagnated for a while, leaving a line of jumbled sediment where its margin had been.  This is probably what created the wacky shoreline of Lake Namakagon – with many shallow bays and great fish habitat.

Even the towering spectacle of Mount Telemark owes its existence to the glaciers – rivers flowing on top of the melting ice carried rocks into a large crevasse.  When the glacier melted, a 1,700-foot-tall pile of sand called a “kame” was left behind. It is the tallest kame in Wisconsin.

Not only did the glaciers shape the physical landscape, they, by extension, continue to impact the human uses of it.  Unlike regions to the south and north, we don’t have extensive farming.  Not only are there too many hills, but the soil just keeps growing more rocks. First, water to percolates underneath buried rocks. When it freezes, the ice crystals lift up the bigger rocks and sand falls underneath. Over many freeze-thaw cycles, the rocks come to surface, right in your carrot patch! Happily, many trees grow just fine in this type of soil, so our local crops are forests instead of corn.

The next time you’re out for a spin on a lake, road or trail in Northern Wisconsin, take a moment to appreciate the wonderful legacy of the glaciers.

Subnivean Chronicles

Adventures in the woods lately have revealed fewer species than earlier in the winter. Have you noticed a change? Tracking stories these days are mostly written by little feet, and many of the stories lay hidden below the surface. Now that we actually have a thickness of snow on the ground, a new world develops beneath our feet. This ephemeral habitat is called the Subnivean layer. Since I first learned about this hidden zone as a bright-eyed college freshman, it has taken on a mythical quality in my imagination. Subnivean sounds like it could be a region of Narnia ruled by the White Witch, or perhaps an outpost neighboring Rivendell in Middle-earth.

The Subnivean layer, like so much of life on Earth, owes its existence to the unique chemistry of water. When frozen, water becomes light an airy, a wonderful insulator. Just as down feathers in your jacket trap a layer of air next to your body, retaining the heat you radiate, a six-inch layer of snow traps air that retains heat from the Earth. We don’t have hot-rock geothermal here, no geysers or hot springs. Our ground warmth, used in many local geothermal heating and cooling systems, comes not from radioactive decay in the Earth’s core, but simply from sunlight absorbed into the upper layers of soil and stone.

Because of this insulation and radiating heat, a thin zone opens up under the snow, right at the surface of the ground. As water freezes, it releases a tiny bit of heat, and as it melts, it absorbs a tiny bit of heat. In this way, the temperature in the Subnivean zone is regulated at a pretty stable 32 degrees Fahrenheit. Compared to -20 with a 15mph wind at the surface, that feels pretty balmy!

Many tracks are now being pressed invisibly into the leaf litter that carpets the Subnivean layer. Shrews, voles and mice, small mammals depend on this habitat for food, warmth, and protection from predators. Their presence is betrayed where the tiny jumping tracks of a deer mouse connect small trees with fallen logs. The tunnel of a shrew will suddenly exit the snow at the edge of a ski trail or where snowshoes have packed down a trough. The impossibly small holes can be not much wider than ½ inch. Sometimes shrews and voles will tunnel through the surface of the snow, especially the fluffy stuff, leaving a winding trough that ends in another hole when they again descend into the fabled Subnivean layer.

Although soft and concealing snow may seem like a perfect security blanket, the fat and juicy prey are not safe from their wily and well-adapted predators. Owls can hear mice through the snowpack, triangulate the sound with their asymmetrical ears, and bust through the crust with fisted talons. Foxes and coyotes can also hear and pounce through the crust, thus securing a meal without even seeing it. Our three smallest weasel species – long-tailed, short-tailed and least, are long and skinny with short legs for a reason. They can snake their way through mouse and chipmunk tunnels to catch the critters right in their own dens. Then the weasel will feast and nap at the warm hearth of its meal before going out to eagerly search every tree, log, rock and stump for another tasty treat.

You may also have noticed the prolific squirrel tracks, connecting trees to small holes littered with leaf shards and pine cone scales. Red squirrels will tunnel to find food caches stored last fall, and often put a big hole in the ski track in the process.

Grouse also make use of the warm blanket that snow provides. When the snow is deep enough, they may “roost” by doing a swan dive, leaving no tracks that would lead a predator to their warm bed. In bad weather, a grouse may stay in its burrow for a few days. Back-country skiers and snowshoers tell stories of grouse flushing from these secret burrows just inches in front of their next step.

While many tracking stories are hidden these days, it’s fun to imagine the complex chronicles unfolding in the Subnivean world. What lies beneath the smooth white surface? More than we will ever know.

Seeing Things

As I came around the corner, a dark blob at the edge of the road caught my eye.  You know how we are always seeing things that aren’t there?  Mailbox reflectors turn into deer’s eyes in our headlights. Tall stumps look like black bears.  Clumps of leaves take on the shape of an owl.  The dark blob was less than three feet tall.  It had pointy ears and a sloped back.  It was black against the bright mid-day sunlight and white snow.  Then, in an impossible moment, it went leaping back into the tangled fir thicket.

Bobcats aren’t rare in Wisconsin, but I’ve only found one set of their tracks in all the miles of trails I’ve hiked and skied in Wisconsin.  Actually seeing an animal make tracks is an excellent learning opportunity, so of course I stopped the car in an open stretch of road, put on the blinkers, and went over to check out the disturbed snow.  Since the flakes were light and fluffy, none of the four toes were visible in the tracks.  I could tell generally where the wild feline had walked calmly up to the edge of the road, sat down for a bit, and then hurried off with big poufy bounds. 

If I hadn’t seen the actual cat, I don’t think I could have identified its tracks.  I could tell, by the size of the body and size of the tracks, that this was not a lynx.  Canada Lynx, with their four-inch wide, snowshoe-like feet, have never been abundant in Wisconsin, since they prefer the deep snow and thick conifer habitat of their favorite prey—snowshoe hares.  Some years, when the snowshoe hare population in Canada crashes, lynx will wander down to Wisconsin to find food.  There hasn’t been a sighting in Wisconsin since 1992, and only 28 verified records since 1870.  Because lynx are so rare here, they are listed as a Protected Wild Animal, but not as a State Endangered Species.  They are on the federal list.  Bobcats can be trapped and hunted.

A few weeks ago in Minnesota’s Cascade River State Park, I watched as a bobcat walked up the trail toward me. It chose a soft place in the pine needles and laid down for a catnap, or perhaps it was waiting in ambush for a squirrel.  Some minutes later it stood and stretched.  Maybe it wasn’t hunting as much as digesting, since it paused then to squat and deposit a long, dark hair-filled scat.  With that business taken care of, it walked daintily down the trail.  A string of oval tracks just smaller than my lip balm were pressed into the light dusting of snow.

Don’t you believe me?  I watched it happen, just like a movie, in my mind’s eye.  The body print was just so on the pine needles, the four tracks of a squatting position had an extra sharpness due to added pressure and time.  The scat was positioned exactly where you’d expect it to be.  Poet Mary Oliver tells a similar tale from deer tracks in The Pine Woods, and challenges us, saying “But I don't believe only to the edge of what my eyes actually see in the kindness of the morning, do you?” 

Was I seeing things?  Absolutely, and that is the very essence of tracking.

Constructive Interference

“Oh wow!  Look at the size of that turkey!  I never realized how beautiful their feathers are – check out the iridescence.”

The mount of a wild turkey in flight is one of the most-exclaimed about objects in the Museum’s Collections Room.  The 5,000 feathers on a turkey are worth noticing, with their rich browns, shimmery copper, iridescent blues and greens, and elaborate black designs.  Some of the colors are a result of pigments, those molecules that absorb certain wavelengths (colors) of light and reflect others.  Melanin is a common pigment in nature, and does more than make things appear brown.  It can also protect against bacteria and fungus, UV radiation, and high temperatures.  A certain type of fungus appears to be able to use melanin to capture the energy of gamma rays for photosynthesis!

Melanin can’t make a turkey, or a seashell, or a butterfly, or a soap bubble shimmer, though.  The vivid, shifting, enchanting colors of these objects are caused by the structures themselves, not a type of pigment. Remember that light travels in waves, and the color of light is determined by its wavelength.  Red light has longer wavelengths, while purple light has shorter wavelengths.  The rest of the colors fall between in rainbow order. 

When light passes through a thinly layered substance, the light bounces off the back surface toward your eye, and joins light bouncing off the upper surface toward your eye.  Where the waves of light overlap, they interfere with each other. The interference can be either destructive, where the waves cancel each other out (so you see black on an iridescent object), or constructive, where the waves amplify each other.

I experienced constructive interference on a macro scale last fall on a sea kayaking trip in Maine.  As we paddled along the seaward side of an island, waves bouncing off the rocky shore grew bigger and bigger as they overlapped with constructive interference. The color of my face changed from pink, to green, to white, as waves striking me from various angles tossed my kayak gawkily.  Iridescent colors also change when you alter your angle relative to the object, because the wavelength of light that reaches your eye changes.

Turkeys in Wisconsin have experienced destructive and constructive interference before, and not just in their feathers. These large game birds are native to southern Wisconsin, but were hunted almost to extinction by 1881.  Major reductions in their habitat due to logging and farming, plus diseases introduced in domestic fowl were also culprits of their decline.

In 1976, the Wisconsin DNR made a trade with Missouri to bring wild turkeys back to Wisconsin.  We gave them ruffed grouse in return. From the initial release site in Vernon County, turkeys recovered enough to move naturally and with help to other suitable habitats across the state.  Many other states have similar stories. The turkey population in United States was once down to about 30,000 birds.  Now it is over 7 million! 

It’s no surprise, then, that many Museum visitors have reported turkey sightings this winter. Their favorite times to forage are morning and evening, which corresponds nicely to most of our commutes. There are two flocks just in my 10-mile commute on County Hwy M.  After the holidays, I returned home to a whole flock of turkey tracks in my driveway and around our bird feeders.

Although northern Wisconsin isn’t their traditional habitat, we do have plenty of oaks for acorns and large white pines near water for roosting. While you might feel sorry for turkeys during harsh winters, the DNR does not advise feeding them.  To provide a turkey with enough to food to impact its survival would take a lot of food!  Any winter mortality is easily made up for by high breeding success.  Feeding can actually harm turkeys, because concentrated groups spread disease more easily, and become easy targets for predators.  If you want to help these beautiful birds, think about managing your forest for mast trees like oaks, and big pines and hemlocks for roosting.

The wild turkey was once lauded by Benjamin Franklin as a more respectable national symbol than the bald eagle, who eats road kill. Franklin wrote: “He is besides, though a little vain & silly, a Bird of Courage, and would not hesitate to attack a Grenadier of the British Guards who should presume to invade his Farm Yard with a red Coat on.”

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Bark

Finally, we're past "stick season" and snow makes it feel like true winter.The long slant of afternoon sunlight illuminatesintricate patterns of tree bark.Instead of a haze of green, trunks stand out as individuals.Some say that a tree's bark is as unique as your fingerprint.While I have yet to find a study that proves it, I have noticed that bark, even within the same species of tree, is incredibly variable.The age of a tree, its health, its growth rate, and its habitat all have an effect on the pattern of its bark.

While skiing or hiking through the forests around here,I tend to entertain myself by identifying plants while zooming down hills.Bark patterns among different species are fairly distinct once you know what to look for.In general, the fissure pattern in bark is a result of the genetics of the tree species, and the way trees grow.

Here's a riddle:If a pirate buries treasure underneath a tree and marks the tree with an X five feet above the ground, and the tree grows one inch taller per year, how high will the X be in 100 years?

The answer, of course, is about five feet, depending on local soil erosion.Trees only grow taller from the tips of twigs.Trees do get bigger around, but only by adding new layers of cells just under the outer bark.And there lies the key to bark patterns.

The center of a tree is dead; in fact, most of a tree is dead!In the trunk there are several layers of different cells.Xylem and phloem are two types of transport tissue. Xylem, which is dead at maturity, carries water and minerals up from the soil. Old xylem becomes what we think of as wood, and makes up the bulk of a tree's mass. The living phloem carries sugars down from the leaves. They have a layer between them called the vascular cambium, which creates the new xylem and phloem cells. Cambium is made of undifferentiated cells that can become anything - like stem cells. These three layers are considered the "inner bark."

Outside the phloem is the cork cambium.Just like the vascular cambium, the cork cambium produces a layer of cells inside it (living phelloderm cells), and outside it (dead, air-filled cork cells).These three layers make up what we call "outer bark."

As the cambium layers create new cells, the tree expands just under the cork layer.Since the cork is dead, it can't stretch or grow to accommodate the larger girth.The bark cracks instead, and eventually sloughs off like dead skin.I think that paper birch has such smooth bark because it peels off instead of cracking.

Why do trees need bark anyway? Outer bark is the armor of a tree, and it protects the inner bark.There is something very tasty hiding in the inner bark.Think ahead to maple sugaring season and you'll know what I mean.Insects, fugus, bacteria, yellow-bellied sapsuckers, deer, moose, snowshoe hares, porcupines, humans and many other things want the sugar created by photosynthesis and transported in the phloem.

Outer bark, like our skin, can help keep these invaders out, or scar over an injury when they break in.Also like skin, bark slows water loss, allows certain gasses to be exchanged, and protects from intense sunlight. The pigments in colorful bark, like on red osier dogwood, act as sunscreens; while greenish bark, like on aspens, can photosynthesize. Bark can also protect trees from extreme cold andheat, including fire.

One of the "active ingredients" in bark is a chemical called tannin.You may have encountered tannins in the way your mouth feels dry and puckery after drinking wine or eating unripe fruit.Tea also contains this bitter brown chemical, and the tea-colored water in bogs is the result of plants steeping in water and releasing the soluble tannins.

Tannins provide a unique defense mechanism against herbivores.Condensed tannins bind with proteins and inhibit digestion.That's one reason that animals tend to eat the newest twigs and softest bark - they have fewer tannins.The ability to bind with proteins made tannin useful to humans, too.We used it for many years (and some primitive skills buffs still use it) in the tanning of hides to produce leather.The tanning process makes leather more flexible and resistant to bacteria. Hemlock bark was once a source of tannin for the leather industry.

Bark from various species also supplies us with spices (cinnamon), medicines (quinine), resin, latex (rubber), poisons, landscaping mulch, and cork (for that wine!). We can also fashion it into cloth, rope, canoes, roofing,dyes, and baskets.

So when the sun's rays sweep through the afternoon forest, take a moment to enjoy the wonderful colors, textures, and patterns of the beautiful, protective, and very useful bark.