Earliest Date for Winter Solstice

December 20 is the earliest date on which the winter solstice can occur (more commonly on December 21 or 22, but we need a topic for December 20).  It is the shortest day of the year, and consequently has had special meaning to humans throughout our history (people today celebrate the summer solstice at Stonehenge in England, but ancient people celebrated the winter solstice there).  The winter solstice is variously called “mid-winter” or the first day of winter, depending on the country and custom.

Arctic tern (photo by Kristian Pikner)

            But that doesn’t matter for our purposes—suffice to say that when the winter solstice comes around, never feat—it is winter!  And nature knows this all too well, so let’s reflect a bit on how animals in the far north respond to winter.  Scientists have categorized the general ways of surviving winter into three strategies, exemplified here by a champion of each.

            The first is to “get out of Dodge,” or in this case, winter.  Many animals migrate to escape the rigors of winter.  Birds, of course, are the most obvious, and the grand champion is the Arctic tern.  Arctic terns (Sterna paradisaea) spend the summer in the Arctic, where they breed, but head south for the winter, really far south.  They fly to Antarctica and back, an round-trip of about 24,000 miles!  In fact, they are avoiding two winters each year, one in the north and one in the south.  Other animals make less dramatic migrations.  Elk, for example, move from high mountain elevations in summer to lower elevations in winter, where the snow isn’t so deep and forage is more available.

Marmot (photo by Andrew Htichcock)

            The second strategy is to hunker down and pretend winter isn’t happening, saving energy by going dormant.  Different animals utilize various levels of dormancy, from simply digging dens and filling them with food, to the official state of hibernation.  The yellow-bellied marmot (Marmota flaviventris), a high elevation relative of the squirrel, is the champion.  It hibernates for as many as 200 days each year, from September or October through April or May, depending on the habitat.  A colony of 10-20 individuals digs a common burrow that they line with grass.  They fatten up in the fall and then cuddle together in the marmot version of grandma’s feather bed.  A hibernating marmot reduces its body temperature as low as 41 degrees Fahrenheit, slows its heart to as low as 30 beats per minute (compared to 180 when not hibernating), and breathes only about twice per minute.

Snowshoe hare (photo by Denali National Park and Preserve)

            The third strategy is to just make do.  Humans throw on another layer, insulated gloves and hats—and wild animals do the same.  Mountain goats and many other grazing animals sport heavy undercoats made up of hollow hairs that insulate their bodies.  The pika, a small rodent, has tiny ears and tail, proportioned to reduce heat loss.  Many northern animals shed their brown summer coats for white fur or feathers, including ptarmigans, Arctic foxes and hares, giving them camouflage as either prey or predator. The snowshoe hare (Lepus americanus) is the champion, however, with thick stiff hair covering its large paws, allowing it to travel easily across deep snow on namesake “snowshoes.”

            Nature has perfected these amazing responses to winter over a very long time.  And that leads to the compelling question of sustainability:  What will happen with global warming?  We can imagine all sorts of bad impacts—like species coming out of hibernation too early and then falling victims to late winter storms.  Less Arctic ice means shorter hunting seasons for polar bears—and we’ve seen the sickening photos of starving bears. The survival of prey animals, like ptarmigan and snowshoe hare, is also compromised because their molting from brown to white coats is triggered by day-length, not temperature.  In a warming world, a white ptarmigan on bare ground is, figuratively, a sitting duck.

References:

Cornell Lab of Ornithology.  Arctic Tern.  Available at:  https://www.allaboutbirds.org/guide/Arctic_Tern/overview#.  Accessed December 9, 2019.

Elischer, Melissa.  2015.  Animal adaptations for winter.  Michigan State University Extension, December 10, 2015.  Available at:  https://www.canr.msu.edu/news/animal_adaptations_for_winter.  Accessed December 9, 2019.

National Park Service.  Marmot, Rocky Mountain National Park.  Available at:  https://www.nps.gov/romo/learn/nature/marmot.htm.  Accessed December 9, 2019.

National Park Service.  Snowshoe Hare.  Available at:  https://www.nps.gov/articles/snowshoe-hare.htm.  Accessed December 9, 2019.

National Snow & Ice Data Center.  All About Snow – Snow and Animals.  Available at:  https://nsidc.org/cryosphere/snow/animals.html.  Accessed December 9, 2019.

Peterson, Christine.  2018.  How Climate Change Affects Winter Wildlife.  The Nature Conservancy, December 06, 2018.  Available at:  https://www.nature.org/en-us/about-us/where-we-work/united-states/idaho/stories-in-idaho/winter-animal-adaptations/.  Accessed December 99, 2019.

This Month in Conservation

February 1
Afobaka Dam and Operation Gwamba (1964)
February 2
Groundhog Day
February 3
George Adamson, African Lion Rehabilitator, Born (1906)
February 4
Congress Overrides President Reagan’s Veto of Clean Water Act (1987)
February 5
National Wildlife Federation Created (1936)
February 6
Colin Murdoch, Inventor of the Tranquilizer Gun, Born (1929)
February 7
Karl August Mobius, Ecology Pioneer, Born (1825)
February 8
President Johnson Addresses Congress about Conservation (1965)
February 8
Lisa Perez Jackson, Environmental Leader, Born (1982)
February 9
U.S. Fish Commission Created (1871)
February 10
Frances Moore Lappe, author of Diet for a Small Planet, born (1944)
February 11
International Day of Women and Girls in Science
February 12
Judge Boldt Affirms Native American Fishing Rights (1974)
February 13
Thomas Malthus Born (1766)
February 14
Nature’s Faithful Lovers
February 15
Complete Human Genome Published (2001)
February 16
Alvaro Uglade, Father of Costa Rica’s National Parks, Born (1946)
February 16
Kyoto Protocol, Controlling Greenhouse-Gas Emissions, Begins (2005)
February 17
R. A. Fischer, Statistician, Born (1890)
February 18
Julia Butterfly Hill, Tree-Sitter, Born (1974)
February 19
Lincoln Boyhood National Memorial Established (1962)
February 20
Ansel Adams, Nature Photographer, Born (1902)
February 21
Carolina Parakeet Goes Extinct (1918)
February 22
Nile Day
February 23
Italy’s Largest Inland Oil Spill (2010)
February 24
Joseph Banks, British Botanist, Born (1743)
February 25
First Federal Timber Act Passed (1799)
February 26
Four National Parks Established (1917-1929)
February 27
International Polar Bear Day
February 28
Watson and Crick Discover The Double Helix (1953)
February 29
Nature’s Famous Leapers
January February March April May June July August September October November December