Sea Turtles

Description

Sea turtles are reptiles remarkably suited to life in the sea. Their hydrodynamic shape, large size, and powerful front flippers allow them to dive to great depths and swim long distances. These front flippers are long, narrow, and winglike, while their hind flippers are shorter. Although sea turtles can remain submerged for hours at a time while resting or sleeping, they typically surface several times each hour to breathe.

There are seven species of sea turtle: the green sea turtle, Hawksbill sea turtle, loggerhead sea turtle, olive ridley sea turtle, Kemp’s ridley sea turtle, leatherback sea turtle, and flatback sea turtle.

Sea turtles are among the oldest creatures on Earth and have remained essentially unchanged for 110 million years. In most sea turtles, the top shell—or carapace—is composed of many bones covered with horny scales, or scutes. Unlike their terrestrial relatives, they cannot retract their heads into their shells. The smallest of the sea turtles are the two species of ridleys, weighing in at 85 to 100 pounds (38 to 45 kilograms) as adults. Leatherbacks are the biggest and can grow to 2,000 pounds (900 kilograms). Most sea turtles grow slowly and have a lifespan of many decades.

Range

Of the seven sea turtle species, the flatback is the only one not found in U.S waters. It is only found off the coasts of Australia.

Life History

Mating occurs roughly every two to three years in shallow waters. In summer, an ancient reproductive ritual begins when the female leaves the sea and crawls ashore to dig a nest in the sand. She uses her rear flippers to dig the nest hole, then deposits 80 to 150 eggs that look a lot like Ping-Pong balls.

When egg-laying is complete, the turtle covers the eggs, camouflages the nest site, and returns to the ocean. Nesting turtles may come to shore several times in a nesting season to repeat the process.

As is true for some other reptiles, the temperature of the sea turtle nest determines the sex of the hatchlings. Warmer temperatures produce more females, whereas cooler temperatures result in more males. For this reason, conservationists and wildlife managers leave turtle eggs in their original location whenever possible so that sex ratios are determined naturally.

After incubating for about two months, the eggs begin to hatch. Hatchlings range from 1.5 to 3 inches (3.8 to 7.6 centimeters) in size, depending on the species, and emerge from the nest as a group. This usually occurs at night, and the hatchlings use the bright, open view of the night sky over the water to find their way to the sea. After their first frantic crawl from the nest to the ocean, male sea turtles never return to the shore again, and females come back only long enough to lay eggs.

Artificial lights on beachfront buildings and roadways—often called light pollution—can distract hatchlings on their way to the ocean. Because of this danger, many beachfront communities have adopted lighting ordinances requiring lights to be shut off or shielded during the nesting and hatching season.

Conservation

All sea turtles are threatened or endangered. They face an uncertain future due to threats of many kinds, including pollution and the encroachment of coastal development on their nesting beaches. They are also susceptible to accidental drowning in fishing gear and are at risk from the international trade in turtle meat and shell products.

In the United States, the U.S. Fish & Wildlife Service and the National Oceanic and Atmospheric Administration's National Marine Fisheries Service have joint jurisdiction for marine turtles: the National Marine Fisheries Service has the lead in the marine environment, while the U.S. Fish & Wildlife Service has the lead on the nesting beaches.

Fun Fact

Sea turtles are toothless, but have powerful jaws to crush, bite, and tear their food.

Sources

Animal Diversity Web, University of Michigan Museum of Zoology

Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission

National Marine Fisheries Service, National Oceanic and Atmospheric Administration

Sea Turtle Conservancy

U.S. Fish & Wildlife Service