What animal in our local area can go into a deep freeze in winter and come out of it in spring?
Gary Johnson says that creature is the wood frog, which had mated, laid its eggs, and left town by the time a group of 10 people visited its vernal pool in an exploration hosted by the Mattapoisett Land Trust on April 17.
“Wood frogs stay in the leaf litter and actually freeze,” said Johnson, who grew up in western New York state where the forest drew his interest as a child. “They put glucose into the cells of their body at a hundred times what a human has in terms of glucose. So, they’re doing research trying to figure out, ‘Wait a second, how can animals do that?’ They load themselves with glucose [and] when warmer weather comes, they just thaw out.”
For the MLT treasurer and past president, the mysteries of nature and what can be discovered in so much as a walk through the woods continues to be a rewarding adventure.
“I’m a little worried that, with global warming – because we’re near the southern boundary of wood frog habitat – and if we don’t have cold enough winters, I’m not sure we’ll have wood frogs much longer,” said Johnson, who was supported on Saturday’s exhibition by MLT president Mike Huguenin and MLT Board of Directors member Wendy Copps.
Sitting under overhanging trees and also partly covered by fallen trees, the vernal pools in coastal Mattapoisett are obscured by thick forest and are therefore not visible from the sky.
“This is a classic vernal pool…. This pool won’t exist in August,” said Johnson.
Vernal comes from the Latin word for spring, and that’s about how long a vernal pool lasts before drying up into a muddy mass.
“They don’t have enough oxygen for fish,” said Johnson, describing the short season that draws wildlife for mating and hatching.
While the wood frogs have already come and gone, their eggs have been left behind to grow and hatch. Salamanders and insect-like invertebrates also lay eggs that are presently growing inside jell masses anchored on fallen tree limbs.
“They’re there to mate and then they’re gone…. Maybe not even a week, they’re there like a few days. They’re done, they go back to the woods,” said Johnson.
Wearing tall rubber wading boots, he carefully climbed into the pond and inspected areas where a giant tree had fallen into the pool. He reached in with a white net and gently untethered a variety of jelled masses housing eggs.
One he pulled from the water looked like an insect, but Johnson confirmed that is was not. It was a log-cabin caddisfly larva. What looked like a thick, black insect in the palm of Johnson’s hand was actually loose pieces of debris that the newly hatched caddisfly pulled on as a coat until it was ready to confront the world.
“The other nice thing about vernal pools – I mean, you would think aren’t these a horrible source of mosquitoes – but they’re not. Because they’re filled with tadpoles and salamanders, they feed on mosquito larvae, so vernal pools aren’t really a big source of mosquito problems,” said Johnson, who noted that the more domestic occurrences such as a discarded tire with standing water inside is a welcome mat for the seasonal pest.
Johnson carried a plastic tub out of the pool that, at first glance, looked like muddy green water. But there was movement of tiny, half-inch-long tadpoles swimming about, almost indiscernible without complete stillness of the water and perhaps a magnifying glass. The egg material, still translucent, was an indicator of hatching within the prior day or two.
Children, including Ava Duponte, 11, of Mattapoisett, Abel Philbrook, 6, of Marion, and Jonalisa Vieira, 11, of Mattapoisett, were eager to experience the wonders of the vernal pool as Johnson placed the egg masses into their hands.
It was speculated as to whether the vernal pool visited should also be classified as a kettle pond, created by the melting of an ice glacier. “This one’s got a little ridge around it,” said Huguenin, who is soon to visit with a geologist relative and hopes to get an opinion.
On route back from the vernal pool exploration, the group passed by an open area of fallen timber, so Huguenin took the opportunity to explain ongoing efforts to better preserve wildlife on MLT-owned property.
A stone wall running through the woods indicates that the land was once a farm, and the present forest all grew up beginning in the first 20 years of the 20th century when farms were largely abandoned due to poor economics. The resultant forest lacks variety.
By Mick Colageo