The Rise of Turtles
A turtle is one of the most easily recognized of all animals. No other animal looks like it (except for its cousin the tortoise). Its ability to master seasonal climate change allows it to live in fresh water habitats year round. Although turtles disappear from view in the winter, they are safely ensconced in the muddy bottoms of lakes, rivers, and ponds. When the snow and ice cover on surface waters begins to melt in late winter, it is a good time to follow a pond's yearly cycle, remembering that many turtles lead terrestrial lives.
As March turns to April, rising water temperatures create thermal currents that , along with the wind, stir up the pond. The spring overturn of water brings nutrients up from the bottom and mixes them with surface waters. Dissolved oxygen levels rise during daylight hours due to photosynthetic activity in the warming water.1
With the pond awakening with life buried below it, one of earth's most ancient life forms, the turtle, rises from the depths to feed and warm itself. The painted turtle is usually the first to arise in southern New Hampshire wetlands. A long line of these dark-shelled heat absorbers will crawl all over each other if space is limited.
Like other reptiles, they breathe with lungs and lay eggs with leathery shells and bury them in exposed soil to incubate. The plates on their shells grow a new layer each year while the external plate may flake off. Turtles have been around for over 150 million years.
Perhaps the most recognizable of these armored animals is the snapping turtle, which can be found in most every marsh, pond, river, or lake. They prefer soft and muddy bottoms and slow moving water. They can be surprisingly placid in the water (unless you are a duckling swimming above one). On land they will snap and hiss, and even the little ones are quite testy out of the water. Snapping turtles eat mostly cattail roots and dead organisms. This scavenger role helps to keep the water body clean.2 The female snapper lays her eggs, up to 25 in number, deposited in sand 6-7 inches deep, and then she packs down the hole with her feet. The temperature of the nest determines the gender of the offspring. Temperatures of 84 degrees and higher produces females, while temperatures of 80 and below produce males. Somehow, a balance generally works out.
The bog turtle, threatened in the US, is among the smallest and least known of the eastern turtles. They are only 3.5 inches long, uncommon, mostly brown with distinctive orange splotches on each side of the head. They are shy and will attempt to burrow if disturbed. They eat mostly insects, caterpillars, berries, and seeds. Bog turtles emerge from hibernation in April and are active through October. They are inhabitants of swamps, meadows, and poorly drained marshes, as well as bogs. The females bury their clutch of 2-3 eggs in the ground.3
Another rather small and uncommon turtle is the 5-inch long musk turtle, found in eastern North American ponds. It makes use of coats of algae draped over its shell for camouflage. It is a nocturnal scavenger.4
Three species of marine turtles inhabit the Gulf of Maine. The leatherback is the world's largest turtle at 8-ft long and 1500 pounds. After breeding on southern beaches, leatherbacks follow migration of artic jellyfish, their favorite food, to the Gulf of Maine in summer. The leatherback is federally listed as an endangered species.
Both the threatened loggerhead and the smaller, endangered, Kemp's Ridley turtles visit the Gulf of Maine. When sea temperatures remain above 68 degrees, loggerheads and Ridleys must turn south.5
Recently, there was a note about turtles in Time magazine that caught my attention. We have probably all seen videos of female marine turtles struggling up beaches, digging deep holes, depositing lots of eggs, covering the hole, and then heading back out to sea. When the small hatchlings emerge, they have to run a gamut of sea birds, crabs, and other predators to reach the sea. Very few of these babies make it back to deposit their own hopes for offspring in the future.
The turtles I have been reporting on here are not usually very good at protecting their eggs, with the possible exception of snapping turtles whose females dig a hole, cover the eggs, and march over the hole to pack it down with their feet and their sizeable weight to discourage predators.
In the Time article, researchers have discovered that the arrau, a giant south American river turtle, has been displaying maternal instincts by communicating with her offspring while still in the egg in an effort to coordinate hatching times. Babies that dig to the surface all at the same time have a better chance of reaching the safety of the river and avoiding predators. The mother responds to the chirping calls of the hatchlings and shepherds them toward the water. The researchers say that the calls between mother and offspring were missed for decades because they are quiet and low-pitched, just at the threshold of human hearing. Since the discovery of the arrau calls, scientists have recorded vocalizations from other species. These species may also use these sounds to communicate as well.6
1. Caduto, Michael J, Pond and Brook, Prentice Hall Inc., Inglewood Cliffs NJ, 1990
5. Schmitt, Catherine, A Coastal Companion, Tilbury House Publishers, Gardiner ME, 2008
6. Ferrara, Camila, "Turtle Moms Talk to Babies," Time Magazine, February 3, 2023
*Cover photo: Stock image
John is the Director of Science for GOMI and a member of the GOMI Guide Team. John’s interests focus on the ocean environment where he pursues educational adventure travel, research, and recreation by sail, paddle, and scuba. John is the founder and director of Adventure Learning, Newburyport, MA, which has been involved with educational outreach in area schools and recreational programs for teens and adults since 1980. A long-time educator, John was at the forefront of the experiential education movement in the U.S. for 36 years, he taught natural science in the Newburyport Public Schools. John has special interest and expertise in teacher training and standards for learning in math and science. His role has included direct teaching, teacher training, program development, grant writing, and developing partnerships with professionals in the field.