Dear Reader,
Winter is long. There have been plenty of times we’ve wished for the life of a groundhog. One where we polish off Thanksgiving dinner, say “good night” and sleep until the warm winds of spring blow. And while we joke that we’d celebrate never lifting another shovel, it’s no joke that hibernation really is an amazing physiological change.
When scientists or naturalists explain that metabolic rates slow in order to save energy, they are talking about rates slowing to just 1-2% of normal activity. And when experts talk about animals in torpor burning stored fat, they’re not talking about regular white fat, they’re talking about a specialized brown fat that is vascularized and can actually create warmth.
Much research is being conducted to better understand hibernating animals and how these amazing processes can help humans, too. Find out more in this month’s Nature Net News – and don’t forget to grab your snowshoes and visit a Nature Net site this month – and celebrate being awake to see falling snow.
Enjoy,
Brenna & Betsy
The Folks at Nature Net
February
Winter Sleepers
“When he feels the wind blowing through him on a high peak
or sleeps under a closely matted white bark pine in an exposed basin,
he is apt to find his relationship to the universe.”
-William O Douglas
Did You Know?
The list of Wisconsin’s true hibernators includes chipmunks, ground squirrels, woodchucks, jumping mice, bats, and bears*. Other animals, like the skunk are called winter sleepers – they wake up on warm winter days and look for snacks.
*There’s much debate on whether bears are hibernators or winter sleepers.
Hibernation is not just sleeping – it’s a suite of reactions to the winter season, a depression in energy use and metabolic rates. These circannual (yearly cycle) changes include lowered body temperature, and slowed breathing and heart rates.
Interestingly, hibernating animals don’t stay in a state of torpor the entire winter. They go through several brief bouts of warming back up, waking up, and then going back into torpor. Scientists, including a few from UW Madison, are still trying to figure out why animals would use so much energy for a mid-winter warm up.
Scientists are also trying to figure out what triggers an animal to head for their winter dens. Some studies have found that animals subject to the same amount of light and constant temperatures, still want to hole up. While seasonal changes that limit the amount of available energy (in the form of food) may force animals to save energy, some scientists believe genetics also play a role in triggering hibernation.
Check out this article from Conservation Institute to learn about 10 animals that hibernate!
What To Do This Month:
Watch for animals out from their dens at either of these snowshoeing events: Snow Day Saturday, February 7th at Dane County Parks, or Snowshoe the Zoo at Henry Vilas Zoo on Sunday, February 8th.
Learn about Grizzly Bears (and piranhas and man-eating pigs, too) from Joel Sartore at National Geographic Live! on Tuesday February 10th at the Overture Center. Use this link to get tickets and support Nature Net. We’ll see you there!
Instant Outdoor Expert:
How Do They Do That? Brown Fat is the Answer
You may have heard people explain that animals – hibernators and winter sleepers alike – are able to survive the long cold winter thanks to the fat they put on in the fall. This is generally correct but scientists have recently discovered that hibernators possess higher amounts of a special kind of fat than other warm-blooded animals.
Interestingly, researchers have also found that humans babies have this special fat along their upper spine and shoulders. What do hibernators and humans babies have in common? They need to stay warm. This fat, called brown adipose tissue – or brown fat – is different from white fat because it can burn calories (energy) to generate heat.
Biologically speaking, brown fat has more lipid droplets, more iron-containing mitochondria (hence the dark color), and is more vascularized than white fat. Turns out, exposure to cold triggers the brown fat cells into action and heat is produced – a process scientists call non-shivering thermogenesis. This process is important to newborn babies who can’t get up and put on a sweater, and to hibernating animals, especially as they come out of torpor and need to rewarm.
You may have heard about brown fat in the news lately, too. Researchers are now trying to find a link to brown fat and obesity in human adults and even how sleeping in a cooler room may boost brown fat stores.
For Families:
Tricks of the Trail – Snow Tracks
Aldo Leopold wrote of this time of year in A Sand County Almanac: “Each year, after the midwinter blizzards, there comes a night of thaw when the tinkle of dripping water is heard in the land. It brings stirrings, not only to creatures abed for the night, but to some who have been asleep for the winter. The hibernating skunk, curled up in his deep den, uncurls himself and ventures forth to prowl the wet world, dragging his belly in the snow.”
In the story, Leopold follows the skunk tracks to see where they lead, curious about the skunk’s mid-winter ambling. He finds instead other stories in the snow – the melting snow tunnels of the anxious mouse, the less than cautious rabbit who meets its end in the talons of an owl, and of course, the awakened skunk who heads straight for a woodpile, presumably for a snack of grubs. Leopold used tracks and signs of animals to “read” these stories in the snow – and you can too.
Looking closely at animal tracks, denoting the size of the track, the presence of claws marks, the distance between foot marks, and what pattern they make, can help determine which animal was about. Some animals, like the skunk, are called waddlers because their short-legged walk leaves a track of alternating front and hide feet marks. While the deer and fox are called perfect walkers because they step in their own front-feet marks.
Find out more about tracks and signs of animals with this fun activity guide from this Nature Net News.
Featured Nature Net Site:
Bethel Horizons
Bethel Horizons is located on over 548 acres bordering Governor Dodge State Park. Their mission is to develop and perpetuate a physical, social, intellectual, and spiritual environment which strengthens and enhances the understanding of a person’s proper relation to nature, to self, to others and to God.
Programs offered by Bethel Horizons include Art Ventures clay workshops and classes for all ages, Environmental Education programs for school groups and individuals, the Horizons Adventure and Wilderness Center which includes low- and high-ropes challenge courses, and Summer Camps complete with Tepee living quarters and bike or canoe trips.
Bethel Horizons also offers facilities for retreats, conferences and meetings, as well as food service, tent and trailer camping areas, and many hiking trails.
Nature Craft:
Chipmunk from Glove
A glove with a lost mate needn’t be a total loss – it can be up-cycled into a plush friend to warm up with this winter.
Start by trimming the following fingers from the glove – the thumb will become the tail, and the ring and middle fingers will be come the arms. Snip only the tip of the pointer and middle fingers – those will become the ears.
The remainder of the palm will be used to form the body and the head (see diagram and detailed instructions here).
Once all chipmunk body parts are ready, pack them with stuffing, adding pipe cleaners to the tail and legs for stability and shaping.
Use a backstitch to add striping to the tail and then stitch all body parts on.
Black thread for eyes and a wooden bead nose add the final touches.
It’s recommended you use an adult size glove so you have enough material to work with.
If you’re inspired, look for “Happy Gloves” for more crafting ideas – see “Suggested Reading” below.
Suggested Reading:
“Happy Gloves: Charming Softy Friends Made from Colorful Gloves” by Miyako Kanamori
“When Winter Comes” by Nancy Van Laan
“Animals in Winter (Let’s-Read-And-Find-Out Science)” by Henrietta Bancroft & Richard Van Gelder
“How and Why Animals Prepare for Winter” by Elaine Pascoe
“What Do Animals Do in Winter?: How Animals Survive the Cold” by Melvin & Gilda Berger
“Hibernation (Patterns in Nature)” by Margaret Hall
“Time to Sleep” by Denise Fleming
“Don’t Wake Up the Bear!” by Marjorie Dennis Murray
“Old Bear” by Kevin Henkes
“Over and Under the Snow” by Kate Messner
“Frederick” by Leo Lionni
“Bear Snores on” by Karma Wilson
“Not a Buzz to Be Found: Insects in Winter” by Linda Glaser