The Courage of Baby Turtles
Born Without Adult Guidance, Only a Few Snappers Survive
Tiny snapping turtle hatchlings the size of a quarter claw their way up through several inches of soil and find their way to the nearest water unaided by an adult.
A high percentage of snapping turtle nests, such as the dug-out one above, are destroyed by predators. This destruction is very obvious from the remnants of the egg shells scattered around the nest hole.
If and when you ever feel the deck is stacked against you, consider the snapping turtle (Chelydra serpentina). The probability of a snapping turtle egg developing into a young turtle that makes it to adulthood is said to be about one in 1,445 individuals; the probability of survival from hatching to adulthood, one in 133. A look at their life history explains why the odds of a snapping turtle living to maturity are so slim.
The snapping turtles that make it to adulthood spend the majority of their lives in a pond, mating in the early spring after waking up from hibernation. Females rarely leave the water except to lay eggs, and this typically happens in New England in June. After traveling a quarter of a mile or more in search of a sunny, sandy spot, the female selects a site and usually digs several holes, choosing one to receive her 20 to 40 eggs. The first challenge an egg encounters is to make a soft landing in the nest hole. This is often facilitated by the adult snapping turtle when she breaks the egg’s fall with one of her hind legs, and gently guides it down into the hole. There is always the possibility of an egg being damaged by the movements of the turtle’s hind feet as they shuffle sand over the eggs, burying them approximately 6 inches below the surface of the ground.
One of the most potentially hazardous aspects of snapping turtle development is the fact that neither parent guards the eggs while they are developing. The male has stayed put in the pond, and the mother heads back to the water as soon as the eggs are buried, never to provide any care for her offspring. This behavior comes at a price, as various studies have found that 90 percent or more of snapping turtle nests are destroyed, often within 24 hours of when the eggs were laid. Raccoons, skunks, foxes and mink all find turtle eggs delectable, and their acute sense of smell leads them right to the buried eggs. If, as herpetologists theorize, female turtles dig more than one nest hole in order to confuse or mislead potential predators, this ploy is not very effective.
If a nest isn’t discovered and destroyed, and the eggs remain undisturbed, sun will warm the surrounding soil, incubating the eggs. Because they are in a cluster, with some in the middle and some on the outside, the eggs are not all incubated at the same temperature. Studies have found that the temperature of an egg during a specific and critical stage of embryo development determines the gender of the hatchling. Eggs maintained at 58 degrees Fahrenheit produce only females, while eggs maintained at 70-72 degrees produce both male and female turtles. Those incubated at 73-75 degrees produce only males and at 77 degrees only females are produced.
Snapping turtle eggs generally hatch in late August or September in northern New England. A hatchling typically breaks through its egg with a special egg tooth that drops off after birth, then digs up to the surface sometime in the fall. Usually all of the hatchlings emerge from the nest within a few hours or days. Occasionally, the young turtles will remain in their nest under the ground until spring, but because of the relatively shallow depth of the nest and the considerable depth of the frost, this does not occur often in northern climates. When it does, it can spell disaster for the turtles.
Predation on hatchlings and juvenile snapping turtles is heavy during the first year (one in 20 hatchlings will live to see its second year), and only slightly lower during the second and third years.
The hatchlings must fend for themselves from the minute they make their way out of the nest. Once they arrive above ground they must find the nearest body of water without any help from an experienced adult. It is thought that the intense illumination in the sky caused by open water may aid the turtles in their search for ponds. Hatchlings and juvenile snappers often reside in small, shallow streams that feed into or out of ponds. Measuring only an inch long, the young turtles are very vulnerable to predators as well as to desiccation during their�nocturnal migration. Herons, bitterns, hawks, eagles, fish, snakes and bullfrogs await and prey on hatchlings once they reach water. Until their shells reach a length of three inches, they are easy pickings for numerous predators.
If a snapping turtle lives to adulthood, it’s fairly clear sailing. Because adult snapping turtles have no natural enemies (other than humans who have acquired a taste for snapper stew), they usually live a long life and die of old age during the winter. It’s been estimated that 60 percent of the individuals reaching maturity will live to age 50. It almost goes without saying that having overcome the multitude of obstacles that they encounter on their way to adulthood, snapping turtles deserve their long and carefree lives.
Mary Holland is the author of “Naturally Curious: A Photographic Field Guide and Month-by-Month Journey Through the Fields, Woods, and Marshes of New England” and “Milkweed Visitors.” She has a natural history blog which can be found at www.naturallycuriouswithmaryholland.wordpress.com.