Sea Turtles - Cheloniidae | Underwater Asia

Family variety

The Cheloniidae family has only 6 species. All are similar but vary in shape, size and shell pattern.

Size

Adult Sea Turtles vary in size from the smallest, the Olive Ridley (Lepidochelys olivacea) around 70cm to the Loggerhead (Caretta caretta) 213 cm in length.

Behaviour

Turtles are divers’ favourites, usually unconcerned by excited noisy spectators, a turtle will often continue sleeping or feeding allowing divers to get a really good look. Sea Turtles tend to have a lot of character perhaps because of their long life spans, they appear to be wise and knowledgeable.

Being replies and air breathing they have to surface periodically to breathe and are often spotted on their way to or from the surface.

Distribution

Found throughout the worlds tropical and temperate oceans. Some species are very rare due to exploitation for meat, shell and eggs.

Habitat

Sea Turtles are found in coastal waters near seagrass beds and other favourable feeding grounds. Hawksbill turtles are the most common turtle to find on a coral reef as they are the only turtles that eat coral. Sea Turtles can migrate long distances for breeding or to reach new feeding grounds, often through open oceans.

Diet

Sea Turtles are largely omnivores, feeding on sea grass and algae as well as crustaceans, jellyfish, molluscs and small fish. Green Turtles are the only species which as adults are strictly herbivores. Hawksbill turtles are the only member of their family to feed on sponges and soft corals.

Reproduction

Turtles are usually solitary only meeting for courtship and mating which often takes place at the surface and can sometimes involve two or three males competing to mate with a single female. Females lay their eggs a few months later usually returning to the same beach they were born on to make their nests. They climb up above the high tide mark and dig a hole in the sand laying their clutch of soft shelled eggs inside. After re-covering the eggs she returns to the sea, leaving her offspring to fend for themselves from the minute they hatch.

Small juveniles are pelagic, taking shelter in flotsam such a weed rafts and eating first plankton, then small jellyfish and floating vegetable matter. When they reach around 25cm they move to coastal waters and find a suitable home near a good feeding ground.

Defences

The Turtles best defence is its almost impenetrable shell making adults very difficult prey for any but the largest predators with the strongest mouths, such as sharks. As a result Turtles are usually very slow and unconcerned not usually having much cause for caution.

Threats

Because of their placid nature they have proven very easy prey for man. They are prized for their rich meat, valuable shell (especially the Hawksbill) and eggs considered a delicacy in many parts of the world. Despite a ban from most countries Turtles are still widely fished and often die as by-catch after getting tangeled in a net and drowned. Many Turtles also die each yaer as a result of ingesting man made debris, as they are long living and slow breeding they are particularly vulnerable to extinction.

Did You Know?

Turtles are able to navigate the world waters migrating hundreds even thousands of miles to nest.

It is thought they are able to plot their course using the earth’s magnetic field to create a mental map.

Related reefspotter

turtles

Intro

The Cheloniidae family includes six of the seven species of marine Turtle, the only other being the Leatherback Turtle a member of the Dermochelyidae family.

Turtles are a favourite sighting on many reefs still lucky enough to have them. Despite being one of the most endangered Turtle species, the Hawksbill Turtle is the species that you are most likely to see on a dive as they are the only species to live on coral reefs.

They seem to have lots of character and often appear to cry, due to the secretion of salts & fluids from a gland near the eyes.

Popular species 1

Hawksbill Turtle

(Chelinus impracia)

The Hawksbill turtle is one of species most commonly seen by divers, as it often makes its home on or near coral reefs. It is a smaller species of turtle only reaching 1m in length, often found resting on a ledge or munching on coral or sponges.

Popular species 2

Green Turtle

(Chelinus chelonius)

The Green turtle can grow up to 1.5m. Adults are totally vegetarian feeding primarily on sea grass. They can be identified by their distinctive head and short snout and unhooked mouth shape.

Popular species 3

Leatherback Turtle

(Dermochelys coriacea)

Largest family member, can grow up to 2.2m. Unlike other marine turtles the lack of a bony carapace instead it has thick, leathery skin over its back. Found predominantly in the open ocean and very rare near land, unless coming in to lay eggs.

Popular species

Turtles are a highlight of any dive. Here are the species most commonly encountered.

Related Dive Spots

Sipadan

Bohol

Bunaken

FACTFILE

SPECIES: 6

SIZE RANGE: 70-213 cm

DISTRIBUTION:

Found in tropical and temperate regions. Some species are rare due to exploitation.

HABITAT:

Found in coastal waters near seagrass beds and other favourable feeding grounds. Turtles migrate long distances in open ocean.

THREATS:

Prized for their rich meat, valuable shell, and their eggs. Often die as by-catch in nets. Plastic and habitat loss are other major threats. Vulnerable to extinction.

Identification tips

Marine Turtles have excellent eyesight underwater, however, they are quite short-sighted on land.
A gland near the eye releases excess salt and fluids ingested when drinking sea water. These glands also keep the eyes moist when females are on land laying eggs.
The sea turtle’s shell, or “carapace”, is streamlined for swimming through the water. Unlike other turtles, sea turtles cannot retract their legs and head into their shells.
Front fins are used as wings for propulsion, they are large and sensitive to touch.
Sea Turtles don’t have teeth. Instead, their mouths are sharp and beak-like and well-suited for crushing or tearing their food.

Sea Turtles - Cheloniidae