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Sea Turtle Facts for Scuba Divers

By

sea turtle on the beach

A Hawksbill turtle hatchling makes its way to the sea. Only about 1 in 1000 sea turtle hatchlings survive to maturity.

© istockphoto.com

What Is a Sea Turtle?:

The sea turtle is a large, ocean-dwelling reptile living inside a shell. It cannot retract its body parts into the shell as turtles found on land are able to do. A sea turtle's shell, streamlined for swimming, consists of large bones fused together and covered by hard plates, called scutes. Divers and scientists often use the shape, number, and distribution of scutes to identify the species of turtle. Learn About the Different Species of Sea Turtles

Whether leisurely swimming or making a speedy get-away, a turtle's long, wing-like, front flippers propel the turtle forward. The back flippers are used as paddles, and are used for steering. Like the rest of the body, scales also cover the flipper skin.

Where Can A Diver See a Sea Turtle?:

Sea turtles are found in warm and temperate waters around the world thanks to their incredible migration routes. Some turtles have been tracked migrating well over 1,000 miles.

How Do Sea Turtles Navigate Such Great Distances?

Research has shown that sea turtles can detect magnetic fields in the earth. One theory is that turtles navigate according to the angle and intensity of the magnetic field. Imagine having a personal, built-in GPS!

As migratory animals, turtles spend most of their time in open water. But as divers are drawn to a reef, so are turtles. In the Caribbean, for example, divers are often lucky to encounter Green turtles and Hawksbill turtles eating sponges and corals or resting under a reef ledge. Sea turtles may also be spotted in the calm waters of seagrass and mangrove habitats where they come to feed and enjoy the tranquil habitat.

Sea Turtles Breathe Air:

Although they spend their lives in water, sea turtles breathe air. Depending on the activity, they can spend several hours submerged. A sleeping or resting turtle can remain underwater for up to 7 hours! With full lungs, Leatherback sea turtles can dive down to depths of over 1000 meters (3000 feet); the other species of turtles stick to shallower depths. However, all turtles must return to the surface eventually for a gulp of oxygenated air to fill their lungs.

Sea Turtles Have an Excellent Sense of Hearing:

Turtles have eardrums covered by skin, hearing best at low frequencies. This may be why high-pitched noises, like a carabiner banging against a SCUBA tank, often result in a turtle speeding off. Perhaps the speedy exit occurs after realizing that foreign creatures are staring at them! Sea turtles also have an excellent sense of smell and good underwater vision.

Determining a Sea Turtle's Gender Is Difficult:

Most turtle encounters underwater are quick -- turtles tend to race away when divers approach. This makes determining sex very difficult. Males and females can really only be differentiated once they’ve reached adulthood, at which point there are a few clues to aid a diver determine if a turtle is a boy or girl.

The difference in tail thickness and length may be the easiest clue when determining the gender of a sea turtle. Males have long, thick tails extending beyond the tip of the shell; female tails are short and narrow. Another easy tip is to look for long, heavy claws on the front flippers. A male uses these to cling to a female while mating. Finally, male shells tend to be longer and more concave compared to the shorter, dome-shaped shell of a female.

What Do Sea Turtles Eat?:

How do turtles eat if they do not have teeth? A sea turtle's beak (jaw) is adpated specifically to its diet. Like any other type of animal, turtles have differences in their diet between species. To get an idea of what typically makes it on the sea turtle menu, imagine jellyfish, sponges, shellfish, crabs, soft corals, and some will even feast on algae and seagrass. Learn about the particular diet of each turtle species.

Sea Turtle Dating and Mating:

Sea turtle mating season takes place between March and October, depending on the species and the region. Considering that turtles are solitary animals and the ocean is a big place, the uncommon occurrence of spotting turtles mating during a dive or on the surface is spectacular. Even more impressive is the opportunity to watch two males fighting over a female!

When sea turtles reach sexual maturity, both males and females migrate from their feeding grounds to their mating grounds. For females, this is the area where they hatched as babies. Females return to the same area each breeding occasion. The effort required to migrate, mate, and lay eggs is so strenuous that female sea turtles only nest every 2-5 years.

Finally, here is a fascinating fact regarding turtle mating: Females will mate with several males during the season. The sperm packet from each male is stored in the female's oviducts. With each ovulation, sperm will be chosen to fertilize that clutch of eggs.

Sea Turtle Nesting:

Once a turtle's eggs have been fertilized, the next move for the female turtle is to head to the beach. Sea turtles lay their eggs in the sand and then return to the sea. The process is called nesting and begins when the cumbersome female treks from the sea to the top of the beach at night.

Wisely, female sea turtles choose a spot above the high tide line so that the sea will not uncover the eggs. Using a swimming motion with her front flippers, the turtle digs a body pit on the sand's surface. Comically, this also creates a sand storm for the lucky observer as the female throws sand behind her! Using her rear flippers to scoop sand, she then creates an egg chamber. When she can dig no deeper, 50-190 (species dependent) ping-pong sized eggs are laid. The female covers the eggs with sand using the rear flippers gently pats it down. After several hours, the female turtle slowly returns to the water after throwing sand over the nest to camouflage it from predators.

On a side note, female Olive Ridley turtles practice a unique nesting behavior known as an arribada. Hundreds to thousands of females will come ashore to lay their eggs all at the same time. It is unknown what triggers this phenomenon, but it is an impressive sight to see!

What Determine a Baby Sea Turtle's Gender?:

With no mother around, sea turtle eggs are warmed by the sun and sand, and incubate for about 2 months. Nest sand temperature determines the hatchling (baby turtle) gender: above 85ºF (30ºC) produces females; below this temperature produces males.

Mass Baby Turtle Dash:

Sharks, birds, dogs and other wildlife happily feast on hatchlings during daylight. For this reason, eggs typically hatch at night when fewer predators are around to eat them. The group of hatchlings digs out of the nest and races to the ocean as quickly as possible. It is thought that the light of the moon over the water guides them to the ocean. During this short journey, the earth’s magnetic field leaves an imprint on the hatchlings, which will guide them back to this same beach when they reach sexual maturity.

Once in the water, hatchlings spend anywhere from a few months to a few years floating with the oceanic currents. Floating mats of Sargassum algae often serve as food and refuge for the little ones as they slowly mature.

The Take-Home Message About Sea Turtles:

Sea turtles are exciting to watch on a dive. A diver's appreciation for sea turtles increases when he understands the difficult life-cycle of sea turtle. Just think -- the turtle you see on a dive is one out of a thousand turtle hatchlings that survived to maturity! Unfortunately, sea turtles are endangered. Learn more about the threats facing sea turtles.

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