Bearly Awake

Black Bears Emerge from their Winter Slumber

Many of my friends bemoan April in the Northeast as one of the worst times of the year. Dirt roads turn into mine fields of muddy ruts and potholes, melting snow and flowing springs turn trails treacherous and even make off-trail woods-walking messy. The trees are all still leaf-less, as though the mud from the roads is stretching brown fingers high into the sky.  Even the leftover snow is dirt-covered and dingy. 

I always jump passionately to April’s defense in these conversations.  April is one of my twelve most favorite months of the year and hopefully when you know where to look you will love it as much as I do. 

Ramps emerging from the forest floor. Shelby Perry

April is (usually) when most of the snow melts in our region, and while that may be sad for lovers of winter sports, it means that water is once again abundant in our landscape. With that water comes all of the things that rely on it to live, breed, and migrate.  Geese fly overhead, resting at lakes, ponds, and even flooded fields.  Amphibians begin their annual migration to breeding pools, singing merrily for all to hear.  The earliest blooming spring wildflowers start to poke up through the soil, unfurl their delicate new leaves, and drink in the sunlight before the trees leaf out and snatch it all away.  Melt water trickles down into the ground, displacing the gasses in the soil that have accumulated from winter decomposition, and releasing what we all think of as the quintessential smell of spring, geosmin.  April in Vermont is magic, if you know where to look. 

One of my very favorite signs of spring, and one that I often first see in April, is black bear (Ursus americanus) tracks. Sometimes staggering, sometimes determined, the prints tell the tale of one of our region’s largest wild predators, and spotting them always gives me a thrill. By now black bears are out and about (time to bring in your bird feeders!) and the females might even have some cubs in tow. It’s been a long process for all these bears to den up in the late fall and emerge five months later—a process that goes unseen but is nonetheless fascinating.

Bear tracks across Binney Pond at Binney Hill Wilderness Preserve in New Hampshire. Mike Przybyla

There is some debate about whether or not bears should be considered “true hibernators,” since they don’t dramatically lower their body temperature during their winter snooze. Yet they do spend the winter in a den, mostly sleeping.  Their sleep ranges from deep to light, and they wake regularly to scratch itches, shift positions, and stretch.  During this time their metabolism and heart rate slow down slightly so they burn fewer calories, which come from fat stores they’ve built up over the previous summer and fall. Adult bears rarely urinate or defecate in their dens (though newborn cubs do) because the slow use of calories stored in body fat generates less waste than eating. Bears also possess the impressive super power of “pee-cycling,” meaning they can recycle built-up urea into new proteins. This prevents the waste buildup from becoming toxic.

Bear tracks through mud at a property protected by Northeast Wilderness Trust in New Hampshire. Shelby Perry

Male bears and non-nursing females coming out of their den in the spring might weigh as much as 15-30% less than they did in the fall. Female bears have an extra challenge through their winter survival, as they often are also pregnant when they enter their dens. Mama bears are mostly asleep through their pregnancy, waking briefly to birth their cubs around January, and then hitting the pillow once again. The cubs, born around the size of chipmunks, will then nurse on their semi-comatose mom until spring, when she will emerge from the den up to 40% lighter than she was when she went in. 

Despite all this, bears don’t wake up hungry. Their bodies suppress their appetites starting in late fall, triggering them to stop foraging and start looking for a cozy place to hole up through the cold. Black bears would be unlikely to stay safely in their dens during the winter if they woke up hungry, so a hormone that simulates the feeling of fullness sticks around in the blood at high levels until well after it is warm enough for them to emerge. And when they do venture out they are, as you might imagine, pretty groggy and stiff. A bear may come and go from its den or other shelters several times while recovering from their winter sleep. Early in the process they blearily stumble and yawn, stretch and laze about, just like I imagine that I would if I slept for 5 months. Gradually, they regain their strength and stamina, and eventually their appetite too. To get a sense of the experience, check out this video of a bear in Minnesota waking up over the course of many days.

A mother bear scent-marks with her cub in Vermont. (c) Sue Morse

As mama bears begin to wake, their cubs are around three months old and weigh around six pounds— slightly more than a Chihuahua, but with significantly more fur! Over the summer the cubs stay with their mom. These three cubs were caught on a game camera last spring following their mom across the brand new Bramhall Wilderness Preserve in Bridgewater, VT.

As they wrestle and play their way through their first year of life, they learn what foods to eat, how to climb trees, and other bear necessities before entering hibernation alongside their mom in the fall.  This will be the last time they will share a den though, and the following April they will strike out on their own, seeking new territories where they can begin the cycle anew. 

 

 

Stop and Smell the Geosmin

 

Spring is a time of transformation. The sleepy silence of the cold white winter recedes into a decadent symphony of sound and color, slowly at first, but with continually increasing vigor right on through until summer. There is so much to see and hear during this time of the year that it is easy to overlook one of my favorite spring sensations: the smell.

Usually described as “fresh earth” or “muddy” the smell is one we all know well. I associate it with those hardy little flowers known as spring ephemerals that come up as soon as the ground thaws, producing both flower and fruit before the trees above open their leaves and soak up all of the available sunlight. Trout lilies and spring beauties and trilliums—just writing their names brings the smell of spring to my mind; but it is not these flowers that give us that springy smell. So just what is it that we have to thank for spring’s classic scent?

Spring beauty emerges from the forest floor in April. Photo by Shelby Perry.

It turns out the scent of spring is the very same substance responsible for the earthy taste of beets: a terpene known as geosmin. The name geosmin comes from the Greek words for “earth” and “smell.” Geosmin is produced by blue green algae and certain kinds of soil bacteria called actinomycetes. These bacteria break down plant material, and in the process convert another soil chemical (farnesyl diphosphate) to geosmin in a two-step process.

Geosmin exists in the soil year-round, but its smell is only noticeable under certain conditions—you might notice it when digging into soil, during spring thaw, and after a rain. This is because generally the gas pools in spaces beneath the soil surface and is only detectable when these pools are disturbed, like when digging turns over the soil or water soaks into it, displacing the gasses within. Sometimes the smell of geosmin is apparent before a storm hits, the result of decreasing pressure associated with the approaching weather causing the soils to off-gas geosmin and carbon dioxide that has built up beneath the surface.

With spring in full swing I hope you take the time to get out into the wild, where forests are coming to life and there is so much to see and explore. And while you are out there don’t forget to stop and smell the geosmin.

 

Newts from the Field: Springing Ahead

 

Look to the forest floor for some of the first signs of changing seasons, writes Shelby Perry, Stewardship Director of Northeast Wilderness Trust

In the first week of March I start, even though I know it is too early, but the anticipation pulls me like a magnet.  In my snowshoes I climb the hills outside of town, follow the folding topography to the low spots, and check on them regularly.  The effort is not wasted, for I get to enjoy other harbingers of spring as I go.  At first the signs are subtle: slight swelling of buds, the staggering tracks of skunks in soft snow, heat wells around the trees in the snow pack, a change in bird song.  Then the more obvious signs begin, and my excitement grows: bear tracks, drumming grouse, bits of green, mud!  By the time I trade in my snowshoes for mud boots my path to the vernal pools is well traveled.

Vernal pools begin to come to life in the Northeast anywhere from mid-March in the south, to as late as May in the north and higher terrain.  In central Vermont, where I live, activity in the pools usually gets going around mid-April, though this year could be a bit later because of the deep snow and lingering low temperatures. 

An immense vernal pool at the Muddy Pond Wilderness Preserve in Kingston, MA, protected by Northeast Wilderness Trust in 2018

What makes a pool a vernal pool?  Two things, really: first it fills with water in the spring and dries up completely by late summer; second, it has no permanent inlet or outlet.  These characteristics are important because generally this means that the pool cannot support a population of fish.  Fish gobble up amphibian eggs and larvae, so pools without these voracious predators give the baby amphibians a better shot at making it to adulthood. 

What makes a vernal pool amazing?  So many things!  They are positively teeming with life.  Eastern toads, wood frogs, eastern newts, leopard frogs, spotted salamanders, fairy shrimp, fingernail clams and more can inhabit a single pool no bigger than a parking space simultaneously when activity is at its peak.  Many of the frog and toad species call from the pools, and the chorus can be heard from quite a distance if you approach quietly.  If they hear you coming first though, the calls will cease and not begin again until you leave. 

Wood frog. Photo: © Susan C. Morse

Usually the first arrival at the pool is the wood frog, and they are a fascinating case study of life in the pool.  Wood frogs over-winter in the leaf litter at the ground surface.  They concentrate sugars in their blood just before winter, a process which allows them to freeze solid for over four weeks at a time without sustaining the kind of cellular damage that kills most living things that freeze.  This adaptation allows them to become active as soon as the ground surface thaws in the spring, and as soon as they can move they make their way to the pools, mate, and lay eggs. 

Frog eggs in a vernal pool framed by eastern spotted newts. Photo: © Susan C. Morse

The eggs that don’t end up in the belly of a newt, bird, or mammalian predator hatch in a few weeks and the pool fills with tiny tadpoles.  Nibbling on leaves and algae, the tadpoles start out mostly vegetarian.  Remember though, these pools have no permanent inlet, meaning that when the rains and meltwaters of spring subside the pools begin to shrink.  Naturalist and ecologist Bernd Heinrich once conducted an experiment where he raised wood frog tadpoles in a tank, as long as he kept plenty of fresh water and food for the tadpoles, they stayed tadpoles, for about 8 months!  As soon as he let the water level drop though, and things got a little bit crowded, the tadpoles turned on each other, and swiftly metamorphosed.  Heinrich concluded that when conditions in the pool concentrate the tadpoles, the resulting cannibalism triggers metamorphosis into frogs.  

Spotted salamander. Photo: © Susan C. Morse

Many of the mechanisms that have evolved to allow vernal pool species to survive, including how metamorphosis is triggered in wood frogs, are still poorly understood.  There is so much left to learn from these fascinating little creatures, but sadly amphibian populations are declining around the globe.  A mind-boggling array of factors, from road salt to climate change, habitat fragmentation to invasive pathogens, are all contributing to the detriment of our amphibian neighbors.  The conservation of large, intact blocks of wild forest protects the stage on which the drama of amphibian life unfolds. 

Vernal pool in the proposed Bridgewater Hollow Bramhall Preserve, a landscape that Northeast Wilderness Trust is working to protect in 2019.

Northeast Wilderness Trust is currently working to protect the Bridgewater Hollow Bramhall Preserve just outside of Woodstock, VT.  The property hosts at least two productive vernal pools, and maybe more.  Conservation of the acreage surrounding these pools as wilderness is the best possible outcome for their springtime inhabitants.  Wilderness means no skidder treads will ever crush the frozen frogs in winter, no new roads will crisscross their habitat, and no chemicals used to control weeds or melt snow will ever foul the waters of the pools. 

Please consider making a tax deductible gift today to support the conservation of the Bridgewater Hollow Bramhall Preserve as wilderness.  The frogs and salamanders will thank you!

Keep It Wild,

Shelby