Sunday, July 5, 2009

Turtle Resurrection

Remember this dude?Found this painted turtle on a sandy path on Nantucket back in May. Since then I have been reading, in David M. Carroll's Year of the Turtle that painted turtles in particular are likely to hatch in their underground nests in the fall, but not emerge from the ground until the following spring. Since I'm pretty sure this is a hatchling, that means this turtle's egg was laid back in the spring of 2008. In many species of turtle, hatchlings dig their way out to the sun in the fall of that same year, but if the nest stays above freezing, they may stay over winter before coming out. That's a gamble, of course, since a real cold snap may kill them in their nest. It isn’t known how or why these decisions are made, but the threat of a fast approaching winter in the northern range of species may determine when the little ones come to the surface in the fall or the spring.

But painted turtles, like a few other vertebrates, have freeze tolerance; they can survive temperatures to 18 F and the freezing of 53% of their body water. For days, even weeks, they will stop breathing, their hearts will stop beating, and their blood will cease to flow. Then, as the ground warms up again come spring, they will begin to move.

Of course, all fresh water turtles hibernate during the winter. They dig themselves into the mud in the fall, sometimes up to a foot and half beneath the bottom of a pond. Even with all the water frozen above, the mud temperature might be as high as 42F. Hibernation can last up to six months, six months without drawing a breath. They have nonpulmonary respiration, which allows them to absorb oxygen through their skin and release CO2 the same way. Otherwise, they are in “metabolic depression,” using such a small amount of energy that they experience little if any weight loss.

Writes Carroll, "We are thought strange to ask for quiet in our own name and stranger yet to ask it on behalf of the marsh."

UPDATE: found this good site about local herps.

1 comment:

amarilla said...

In some animals it is unique sugar compounds that help their cells avoid the destructive effects of ice formation in winter. Sugar, good for so many things. But don't drink the antifreeze!