Notes from Halibut Point: Emerging from Winter

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.

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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.

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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"