Delmarva’s Marine Migrants: Sea Turtlesby Jim Rapp
During the summer, naturalist Jim Rapp tells us how one of Delmarva's most ancient marine animals is spotted in our ocean waters and inland bays.
Imagine kayaking or paddleboarding along Delmarva's coast on a tranquil summer day, deep in your own thoughts under the warm sun with the cool, glassy, gently heaving ocean beneath you. You paddle and drift, paddle and drift, keeping the beach a safe, short paddle away, while gazing out over the vast Atlantic to the distant curving arc where sky meets ocean. Suddenly, you're abruptly awakened from your trance by a powerful, explosive gasp behind you. You quickly look over your shoulder towards the sound to glimpse a reptilian head the size of a small melon gulp some air before dipping back into the deep.
What you've just experienced is one of Delmarva's most ancient marine animals taking a life-sustaining breath. Sea turtles can submerge and stay under water for more then 45 minutes on just one breath. Some species can stay under for more than five hours, and dive to more than 1,000 feet. Their large lungs serve as both air storage tanks and buoyancy devices. To conserve precious oxygen, sea turtle hearts beat very slowly. Nine minutes can pass between heartbeats.
Their name indicates their habitat -- these turtles are only found in the sea, and in large, open estuaries, such as the lower Chesapeake and Delaware Bays. You will also find them in our Atlantic coastal bays near the inlets at Indian River, Ocean City, and those south of Chincoteague that slice though Virginia's barrier islands. The upper regions of our bays are used as seasonal habitat for young sea turtles.
Sea turtles have totally adapted to life in the salty ocean. Rather than having useless legs and feet, their limbs are long, paddle-like flippers for swimming strongly. Like all turtles, they have a protective upper shell, but their flippers and heads don't retract into their protective bony armor. The shell is flat and streamlined for swimming efficiency.
Sea turtles need fresh water to survive, but they don't drink the way that other animals do. They get their water from the plants and prey they eat, and they have a special gland near their eyes that rids their bodies of excess salt. Their teary, salty secretions make sea turtles look as if they are crying when on land.
Female sea turtles haul out onto the beach to lay their eggs. Sea turtle nesting on Delmarva is uncommon, but some species will lay their eggs in July and August on the white sands of our Atlantic beaches. Females will crawl ashore and dig a hole in the sand with their back flippers. They will lay between 70 to 190 eggs the size and shape of ping-pong balls, cover up the hole, and head back to the sea.
The temperature of the sand where the eggs incubate will determine the sex of the baby sea turtles. Above 85 degrees Fahrenheit, the young are mostly male. Below 85 degrees, more females will hatch out.
After 6 to 10 weeks, the babies will hatch. It may take the young turtles up to a week to emerge from their sandy nest. They usually crawl out at night, and immediately start scooting over the sand towards the ocean. Many of the hatchlings will get picked off by hungry animals prowling the beach, and even more will get gobbled up by fish in the ocean.
Those hatchlings that survive will soon start feeding. Each species specialize in eating different things, but their diets consist of algae, grasses, crabs, shellfish, shrimp, fish and jellyfish.
Their preference for prey that is translucent or silvery, such as jellyfish and fish, is a problem for sea turtles. One major threat that faces sea turtles in the open ocean is eating marine trash that looks an awful lot like turtle food. Sea turtles have been killed by consuming plastic bags and shiny Mylar balloons, which they can mistake for a juicy jellyfish or a tasty fish.
Their bodies' own structure contributes to this problem. Sea turtles have spines in their throat that point downward towards their stomach, so even if halfway into their meal they realize that their food is garbage, they can't regurgitate. The plastic that is swallowed gets trapped in the stomach, which prevents them from properly digesting food.
One horrible side effect of swallowing plastic is known to sea turtle rehabilitators as "bubble butt." Gas can get trapped in the turtle's body due to their inability to digest marine trash. The gases cause the turtle to float with their butts pointing skyward, which prevents their ability to catch food or evade ocean predators.
Other stringy marine debris, such as monofilament fishing line and drifting "ghost nets," can cause sea turtles to become entangled and drown.
Five of the planet's seven sea turtle species are known to frequent Delmarva waters between May and November, and all are endangered. Delmarva's sea turtle species, from smallest to largest, include the Kemp's Ridley, which weighs in at under 100 pounds, to the Atlantic Hawksbill, Loggerhead, and Green, all weighing between 150 to 450 pounds, to the giant Leatherback, which tops the scales at close to 2,000 pounds.
In addition to problems caused by marine debris, sea turtles are threatened by beach development that can ruin nesting habitat. Beachfront lighting can cause hatchlings to move inland towards the artificial glow cast by lights on buildings and street lamps, which makes it easier for land-based predators to eat the helpless young turtles. Long-term threats from sea level rise may reduce the availability of good nesting beaches. Although protected along the U.S. coast, sea turtles and their eggs are exploited for food in some countries, and the shells of adult turtles are carved into tourist trinkets.
Sea turtles along the Delmarva coast become stranded on the beach usually due to boat strikes and the ingestion of fishing line and tackle. Occasionally, "cold-stunned" sea turtles are found in the late fall and early winter, when water temperatures drop dramatically to below 50 degrees Fahrenheit. The sudden drop in temperature causes the migrating sea turtle to become immobile. If found on the beach or in the water, they may appear dead, but can be resuscitated by sea turtle rehabilitators and delivered to warmer waters in the south.
If you find a stranded sea turtle on Virginia's Eastern Shore, contact the Virginia Institute of Marine Sciences. In Maryland, contact the Maryland DNR. In Delaware, contact the Marine Education, Research and Rehabilitation Institute.
You can also help sea turtles out by picking up trash when you visit Delmarva's beaches and coastal areas, and by participating in one of our many Coastal Cleanup events in the fall. Less marine debris in our ocean and bays equals more happy sea turtles along the Delmarva coast.
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