Green under white

“It was one of those fabulously clear, cold, mid-January days in 1964 when a Massachusetts painted turtle—Chrysemys picta—first intruded into my life. … the class was on a midwinter field trip to Beaver Pond in Lincoln. I was dutifully sweeping the snow off the ice with a big pushbroom; the students were all gathered around, rigging plankton nets and bottom samplers for our assay of the pond’s life. Then, just below the crystal-clear ice, a painted turtle swam by.”

So begins one of many fascinating and illuminating anecdotes in This Broken Archipelago, an engaging natural history of the reptiles and amphibians of the Cape and islands—and hereabouts—by James D. Lazell and former Lincoln resident Martin C. Michener. (Out of print; an updated digital edition including sound recordings is available from EnjoyBirds.com.) The author explains the benign thermoclining of wintry ponds: ice atop and heaviest 39°F water on the bottom; between, a less-dense layer just warm enough for turtles to become active. So even when Farrar Pond looks like this,

there is plenty going on beneath. Other swimmers, as evidenced by the flagged holes and blanketed tents of ice-fishermen, -women and children, are also about and feeding through the chill season. With them, prey (like plankton and various arthropods), parasites (leeches) and predators (bigger fish) keep the circus turning. Torpid frogs, which unlike turtles cannot shift to an anaerobic metabolism to bury deep in isolating mud, lie on the bottom, perhaps moving about occasionally. And frogs-to-be that have not metamorphosed before lock-down remain active under the ice.

Frogs and turtles are not literally “cold-blooded”; rather, poikilothermic: able to regulate internal temperature, hence level of activity (and protection from both freezing and overheating) mainly by moving between warmer and cooler locations. While not thermostatted via metabolism and muscle (shivering) like mammals and birds, larger aquatic creatures, with insulating fat and a greater volume-to-surface-area ratio, can maintain a high body temperature even in freezing water. Tuna and sharks are examples; Lazell also provides an engaging description of the countercurrent blood-warming system used by large sea turtles and aquatic birds to conserve warmth.

This past winter was remarkable in several ways, including exceptionally high and persistent snow cover that gave voles exceptionally high and persistent access to the trunks of all sorts of woody plants. Many a treasured shrub met the spring show denuded; some resprout from rootstock; others are lost.

For the phenologically inclined, early March (sometime between Texas Independence and St. Patrick’s Days) usually brings first movement of amphibians from pond to vernal pool or other breeding haven. Most years, this occurs on the first rainy night above about 40ºF when there is open water. But when mid-February looks like this,

it is a good bet that events will be delayed. By month-end, high groundwater flowing from the banks has opened minimal windows at a few shoreline spots;

And the lily pond? Immured beneath a foot of glacially consolidated snowpack:

Even as the rising sun of early April clears ever-greater areas of open water,

the stairways to mating heaven remain in part chill and slippery (or perhaps adhesive, like licking metal in a Lake Wobegon winter):

Sunlight and scudding winds melt a hand’s-breadth portal into the higher pool;

a door that snaps shut each night:

At last pond and banks are reasonable clear,

revealing one of the rewards for winter-active turtles of the vegetarian persuasion:

While photosynthesis is slowed by ice-limited light (and perhaps CO₂) levels as well as cold, respiration metabolism (that burns through stored sugars) is slowed even more. So algae may grow freely beneath the ice.

With evening temperatures mostly above freezing—and days in the 60s—migrations are still hampered, now by drought. Though the snow came in feet and yards, it fell cold and light, and melted away to not much water. AWOL showers left banks dry, and animals that breathe through their skins do not enjoy rubbing up against dusty leaves. Only on April 8^th, a month late, do a few hardy or impatient migrants begin the long upward trek, joined within days by multitudes. unimpeded

and in some cases supported by an ice-staked leaf net, from which they telegraph presence and intentions:

In most years, frogs collect quietly from a few days to a fortnight, perhaps awaiting some signal of collective biochemistry, day length or temperature. In this belated season, as soon as net and ice roll back to clear a few square feet of open water, a wild and noisy lek begins,

enthusiastic multi-body collisions apparently undamped by the ghosts of collateral relatives haunting the bedchamber, victims more likely of deficient oxygen supply than of actual freezing:

The chaotic multitude condenses into discrete (if indiscreet) pairs

and less discriminate larger groups wherever some kind of footing is to be found:

As this exchange of vital information reaches its natural conclusion,

activity tapers down over a couple of days; most instigators head back downhill, leaving a few to watch gardens grow on the exhalations of their successful labors:

And as these soon emerge into open water, various cousins arrive to reiterate the process according to their own timetables

until again the pool is, on the surface at least

(largely) still: