|
Chilling beauty |
This winter made its mark with a brief ferocity punctuating
a general blandness. Having to reach only occasionally for a snow shovel
counted as a relief to most of us after the exertions of 2015. Some plants and
creatures find deep snow helpful to survival. Others find it a challenge. We'll
see how they fared, case by case.
|
Robins at the edge of
snow |
When I was growing up even suicidal robins didn't stay up
north during the winter. Now we have fluffy-puffy year-rounders getting by on
berries instead of worms. They can't wait for the thaw to get back to their
preferred annelidan delicacies.
|
Beaver lodge, Halibut
Point quarry |
Last summer a beaver took up residence at Halibut Point for
the first time in anyone's memory. We began to notice 'penciling' of waterside
saplings, a small sacrifice of vegetation to support the novelty. Then the
beaver got busy clear-cutting the quarry margins to construct its winter
quarters and food stash.
|
The beaver, from cute
to incorrigible |
The curious naturalist waits to see whether an insatiable beaver
family will emerge from the den to annihilate the quarry's verdant margin. Perhaps
it was just a solitary pioneer who will have to trundle back to the swamps to
find a mate this spring, its single-season alterations second only to human
enterprise in their ecological impact.
Amphibians and reptiles solve their needs with equal
ingenuity but less disturbance. Many of them develop a special relationship
with water during dormancy. Amphibians are all born in the water initially able
to breathe aqueously (usually gills) but eventually developing lungs. Reptiles
are all born on land, breathing air their whole lives. They may or may not turn
to the water, but they never relinquish their lungs.
|
Blanding's turtle at
water's edge |
When I heard that reptilian turtles overwinter in the mud
beneath ponds I decided to read up on what biologists think they know about an animal
accomplishing that feat on a single breath. Almost all hibernating species store
fat and lower their metabolic rates. Turtles make a further choice: submerge. They're
never going to have their cells ruptured by ice crystallization. But breathing
underwater seems no more possible than flying south.
A turtle
derives a small, steady amount of oxygen directly from the water through minute
blood vessels lining its throat cavity. Similar tissues aerate two walled sacs near the anus. So it gets through
the winter with a bit of help from both ends. Its heart that might beat forty
times a minute on a warm day in July drops to one beat every ten minutes in cold
water.
It still
must contend with metabolic lactic acid buildup while sealed for months under
the ice. Doing next to nothing slows the acid buildup, but body functions still
produce enough toxin to kill the creature before winter runs its course. The turtle
dissolves minute amounts of calcium salts from its shell into its bloodstream
to buffer and neutralize the lactic acid.
It's
no wonder that turtles like to bask in the summer sun.
|
Bullfrog, always wet |
Aquatic amphibians such as frogs and salamanders are
able to retrieve all their oxygen from the water through their skin. Their
lungs are relatively primitive. Rather than burying themselves in the mud for
the winter like turtles do they expose their highly vascularized skin to gas
exchanges with the water, whose oxygen concentration increases at low
temperatures. On land or below ground amphibians can rely on cutaneous
respiration by keeping their skins constantly moist with mucous secretions.
Our local wood frog, a terrestrial hibernator, foregoes
submersion. A high concentration of glucose antifreeze in its vital organs prevents
pulverization by ice. A partially frozen wood frog stops breathing. Its heart
stops beating. It looks like a block of ice and appears quite dead. But when its
hibernaculum warms up the frog's frozen portions thaw and resume activity. During
vernal days and nights it celebrates its return from refrigeration below zero
(C) with quacking calls at nuptial ponds.
|
Spring peeper inflating |
Peepers, another freeze survivor, sustain their spring
chorus with multitudes of tiny amplification systems. Though seldom seen they
surround the wetlands walker with quintessential nocturnal charms.
|
A male red-wing
blackbird staking claim from a cattail |
Taking up the spirit migratory red-wings re-animate our dreary
marshes. The serious business associated with their songs, calls and alarms is
easy to recognize without looking up, but spotting their flashing scarlet
epaulets is half the fun.
|
Tufted titmouse foraging
among oak tree flowers |
All winter titmice have enlivened local bird feeders with aerobatic,
bright-eyed, crested, larceny of
sunflower seeds. Now their territorial challenges pierce, scold, seduce. Peter, peter, peter calls from the
treetops sometimes mobilize comically in the driveway against intruding
doppelgangers reflected in car mirrors.
|
An over-wintered Mourning
Cloak butterfly displaying amorously on the woodland floor |
Gentler beauties materialize unexpectedly this month. One
generation of Mourning Cloak butterflies that overwinters as adults in tree
crevices makes the earliest of the papilionoid
appearances. They consummate this accomplishment in romantic flights
across woods and fields. At rest with umber wings folded up they are nearly
invisible against tree bark. Open-winged they splash color into the spring.
At a season with few blooms Mourning Cloaks walk head downward down the trunks of oak trees to feed on sap. They search out rotting fruit, animal feces, and occasionally flower nectar. During summer these cool-season champions might aestivate in a dormant
state similar to hibernation. They suspend physiological functions in diapause
to minimize the hot-dry environmental challenges. They nap.
***
Winter as an arm of the creative forces serves all kinds of
strong-armed functions in the biosphere. It builds soil, manages populations,
directs evolution. It choreographs especially water as its most compelling agent.
To Nature it is inevitable. To us post-Natural humans it claims only respectful
consideration if we're careful, mortality if we're not prepared.
____________________
Further reading thanks to Karen First, Director of the Nature
Preschool at Massachusetts Audubon's Endicott Wildlife Sanctuary in Wenham:
Bernd Heinrich, Winter World
Mary Holland, Naturally
Curious
David S. Lee, "The Complexities of Turtle Hibernation"
(Internet)
Addendum
Emerging also from a two-week sojourn "Appalachian Spring"
Roseate
spoonbill, National Wildlife Refuge, Savannah
Spanish moss,
Charleston
Civil Rights
Museum, Greensboro NC, site of the first Sit-in, 1960
Here vibrated
Black Mountain College on Lake Eden, Asheville
Proprietor's own
stuff, Burnsville NC
Fallingwater
Cascades
Dogwood and
redbud, Blue Ridge Parkway
Wild about phlox
Skyline
Drive
Dr. Marian
Wright Edelman receiving honorary degree at Monticello
Fife and Drum
Corps at Thomas Jefferson's 273rd birthday celebration
Tallest peek in
the mountains
Mr. Bluebird
Luray Caverns
Franklin Delano Roosevelt continues to lead,
Washington DC