Sea Turtles

Species

Leatherback (Dermochelys coriacea) » Top

The Leatherback is the turtle best adapted to low temperatures and because of this is the most widely distributed of all sea turtles. It is estimated that there are between 26,000 and 43,000 female Leatherback turtles in the world of which a maximum of 500 nest at Gandoca. When they are not nesting on beaches these giant sea creatures move erratically through waters where there is an abundance of food. They feed mainly on jellyfish and other soft- bodied prey. The Leatherback is the largest of all sea turtles. They grow to an average 1.5 meters and vary between 1.24 and 2.56 meters. According to the colony, they can reach weights between 200 and 506 kg.

Average weights according to current research are as follows:

  • Costa Rica 258-506 kg
  • Surinam 302-425 kg
  • Senegal 200-250 kg
  • India 272-356 kg
  • Sri Lanka 301-448 kg

Physical Characteristics:

  • the head is small, measuring between 17% and 22.3% of the carapace
  • their upper jaw has two "teeth" projecting downwards
  • their lower jaw has a single "tooth" which fits between the upper teeth
  • their back is covered with a continuous layer of leathery skin (rather than the hardened plates of other sea turtles)
  • the carapace has seven ridges running from front to rear
  • their front flippers are very long and in an adult can equal or exceed the length of the carapace. they are mainly black in colour with white-grey spots and patches
  • they have distinct pink patches normally found on the head and neck.

Distribution

The Leatherback inhabits seas and oceans throughout the world. It can be found in the waters of the Atlantic, Pacific and Indian oceans and occasionally in the Mediterranean sea. Because of its feeding habits it is usually found in tropical and subtropical waters but is also regulary seen in the North Sea, Argentina, Chile, the Gulf of Mexico, the east and west coasts of the United States, Spain and Portugal. The majority of adults spend their time in open waters but little is known about where the new born turtles go once they leave the beaches.

The Leatherback inhabits waters far from the coast and in general only comes to the coast to nest. However, small groups of turtles have been seen moving together in coastal waters, particularly in areas where there are a large number of jellyfish on which to feed.

This species only nests on beaches immediately adjacent to deep waters and in areas that are free from coral. They choose high energy coasts with strong currents and high waves. The nests are normally placed directly after the shoreline. Because of this the flow of the tide can damage the nests.

In the eastern Pacific Ocean there are a large number of nesting sites, particularly on the east coast of Mexico where up to 80,000 nests have been counted in a season. Recently, however, there has been a sharp decline in nesting in this area. Playa Grande in Costa Rica has also seen a decline in the number of turtles nesting on its shores. Other areas in the eastern Pacific where nesting occurs are Panama, Colombia, Ecuador and Peru although at sites in these countries there are no more than 500 hundred nests per season.

In the western Atlantic Ocean nesting sites have been found in Trinidad and Tobago, Puerto Rico, the Virgin Islands, Panama, Surinam, Guyana, French Guyana, Brazil and in Costa Rica - from the mouth of the river Tortuguero to the mouth of the river Matina - and on Gandoca Beach. In the eastern Atlantic Ocean very few nests are found with just a small number on beaches in Africa.

The Leatherback eats all types of Jellyfish including the infamous Portuguese Man o War. The lining of its mouth and throat contain backward facing spines that stop the slippery jellyfish from escaping. Many Leatherback turtles die from eating plastic products that look similar to jellyfish in the water.

Each time the turtle eats a jellyfish it swallows seawater, in order to get rid of harmful excess salt from its body, the turtle continually “sheds tears”.

Hawksbill (Eretmochelys imbricata) » Top

The hawksbill turtle is a critically endangered sea turtle belonging to the family Cheloniidae, is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. While the turtle lives a part of its life in the open ocean, it is most often encountered in shallow lagoons and coral reefs where it feeds on its chosen prey, sea sponges. Some of the sponges eaten by E. imbricata are known to be highly toxic and lethal when eaten by other organisms. In addition, the sponges that hawksbills eat are usually those with high silica content, making the turtles one of few animals capable of eating siliceous organisms. They also feed on other invertebrates, such as comb jellies and jellyfish. (Virginia Department of Game & Inland Fisheries.)

Carapace

Oval, with a strongly serrated posterior margin and thick overlapping (imbricate) scutes (except in hatchlings and some adults); four pairs of costal scutes, each with a slightly "ragged" posterior border; straight carapace length (SCL) to about 90 cm.

Head

Relatively narrow; width to 12 cm; with a straight bird-like beak; two pairs of prefrontal scales. Limbs: front flippers are medium length compared to other species; two claws on each flipper. Coloration: dorsally brown (dark to light) in hatchlings, often boldly marked with amber and brown variegations in juveniles and younger adults; underside light yellow to white, sometimes with black markings (especially in Pacific specimens).

Plastron

Four pairs inframarginal scutes.

Distribution

All oceans, tropical waters.

Weight

To about 80 kg (average about 60 kg). (Pritchard and Mortimer, 1999)

Throughout the world, hawksbill turtles are taken by humans even though it is illegal to hunt them in many countries. Hawksbill turtle shells, the primary source of tortoise shell, is used for decorative purposes. By the Convention on International Trade in Endangered Species, it is illegal to capture and to trade in hawksbill turtles and products derived from them in many nations.

Green Turtle (Chelonia mydas) » Top

Carapace

Broadly oval, margin sometimes scalloped but not serrated, and not incurved above hind limbs; four pairs of costal scutes; straight carapace length (SCL) to about 120 cm.

Head

Anteriorly rounded; width to 15 cm; one pair of prefrontal scales; four pairs of postorbital scales.

Limbs

Single claw on each flipper (rarely, two in some hatchlings).

Coloration

Dorsally black in hatchlings, becoming brown with radiating streaks in immatures, very variable in adults (generally brown, buff, and other earth tones; plain streaked or spotted); underside white in hatchings, yellowish in adults.

Distribution

All sub-tropical and tropical seas. The range of the species extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans.

Like other sea turtles, green turtles are known to migrate long distances between their feeding grounds and the beaches they hatched from.

Weight

The green turtle is a large sea turtle belonging to the family Cheloniidae. to about 230 kg in the Atlantic and western Pacific Oceans, less in the Indian Ocean and the Caribbean. (Pritchard and Mortimer, 1999)

Despite the turtle's common name, it is lightly-colored all around while its carapace's hues range from olive-brown to black in Eastern Pacific green turtles. The turtle is actually named for the greenish coloration of its fat and flesh.

As a species recognized as endangered by the IUCN and CITES, Chelonia mydas is protected from exploitation in most countries worldwide. It is illegal to collect, harm or kill individual turtles. In addition, many countries have implemented various laws and ordinances to protect individual turtles and turtle nesting areas within their jurisdiction.

As an adult, green turtle has few enemies and even fewer predators. Only human beings and the larger sharks are known to feed on green adults. Adult green turtle is primarily herbivorous. It feeds almost-exclusively on various species of sea grasses and seaweed.

Black turtle (Chelonia mydas agassizii) » Top

Some experts consider the black turtles to be a separate specie.

Head

Anteriorly rounded; width to 13 cm; one pair of prefrontal scales; four pairs of postorbital scales most common (followed by three pairs).

Limbs

Limbs may be relatively longer than in other Chelonia populations; single claw on each flipper.

Color Coloration

Dorsally black in hatchlings, remaining dark throughout life; adults may be uniformly black above or with black spots or other markings on a greyish background; underside white in hatchlings but within a few weeks or months becoming infused with gray pigment.

Distribution

East Pacific Ocean.

Weight

To about 120 kg (average adult about 70 kg). (Pritchard and Mortimer, 1999)

Loggerhead (Caretta caretta) » Top

The genus name "Caretta" is a latinization of the French "caret", meaning turtle, tortoise, or sea turtle. Loggerhead is characterized by a large head with blunt jaws.

Carapace

Moderately broad; lightly serrated posterior margin in immatures; thickened area of the carapace above the base of the tail (at the fifth vertebral) in subadults and adults; five pairs of costal scutes, the first (anterior) pair the smallest; straight carapace length (SCL) to about 105 cm in northwestern Atlantic, smaller in some other areas, the smallest adults being in the Mediterranean (to about 90 cm).

Head

Large and broadly triangular in shape; width to 28 cm; two pairs of prefrontal scales.

Limbs

Front flippers relatively short compared to other species; two claws on each flipper.

Coloration

Dorsally light to dark brown in hatchlings, generally unmarked reddish-brown in subadults and adults; underside brown in hatchlings, yellow to orange in subadults and adults.

Plastron

Three pairs inframarginal scutes.

Distribution

All oceans, usually temperate waters, sometimes subtropical and tropical.

Weight

Adults grow to an average weight of about 200 pounds (about 100 kg), and can reach 1m in length.(Pritchard and Mortimer, 1999)

The species feeds on mollusks, crustaceans, fish, and other marine animals, which they crush with their large and powerful jaw. As with other sea turtles, females return to lay their eggs on or near the same beach where they hatched. Unlike other sea turtles, courtship and mating usually do not take place near the nesting beach, but rather along the migration routes between feeding and breeding grounds.

Olive Ridley (Lepidochelys olivacea) » Top

The Olive Ridley is one of the smallest species of sea turtle. It is named for the olive color of its heart-shaped shell.

The nesting population, where solitary nesting is concerned, has been estimated at between 4,500 and 5,000 individuals. Taking into account the Arribada beaches, the population is estimated at 750,000. The most important nesting beach is at Ostional, situated in the Ostional National Wildlife Refuge (Refugio Nacional de Vida Silvestre Ostional). The Nosara beach, located to the south of Ostional, is occasionally used during the large Arribadas by the same nesters of Ostional.

Olive Ridleys are omnivorous, feeding on crabs, shrimp, rock lobsters, sea grasses, algae, snails, fish, sessile, pelagic tunocates and small invertebrates. They are sometimes seen feeding on jellyfish in shallow waters. These turtles forage offshore in surface waters and can dive to depths of at least 150 meters (500 feet).

Carapace

short and wide, but narrower and higher than in L. kempii; high vertebral projections in juveniles; carapace smooth but elevated and somewhat tectiform (tent-shaped) in adults (especially in the East Pacific); five to nine pairs of costal scutes (usually six to eight) often with asymmetrical configuration; carapace scutes slightly overlapping in juveniles, non-overlapping in adults; straight carapace length (SCL) to 72 cm.

Head

Relatively large, triangular from above; width to 13 cm; two pairs of prefrontal scales.

Limbs

Two claws on each flipper (some adults may lose the secondary claw on the front flippers).

Coloration

Dorsally grey in immatures, mid to dark olive-green in adults; underside white in immatures, cream-yellow in adults.

Plastron

A distinct, small pore near rear margin of each of the four inframarginal scutes.

Distribution

Tropical waters of Pacific, Indian and South Atlantic Oceans.

Weight

Typically 35-50 kg. (Pritchard and Mortimer, 1999)

At Ostional, the Arribadas -- massive turtle nestings and egg layings -- occur on a lunar cycle of approximately 28 days. The majority occur around the last quarter of the cycle although this event may take place at any time including the full moon and two Arribadas (first and last quarter) may occur in the same month. The size and duration of the Arribadas varies between the dry and wet seasons. Those occurring in the dry season of January to April tend to be smaller (approximately 5,000 turtles) and of shorter duration (less than four days). In the wet season of May to December, up to 300,000 turtles may lay over a period of eight to 10 days. On a number of occasions between August and October, two Arribadas of 10 days each have occurred in the same month. This results in continuous activity during the month with a few days of lower activity and two peaks of maximum nesting. (Chaves and A. du Toit, Robinson Marine Turtle Research Center).

Kemp's Ridley (Lepidochelys kempii) » Top

Kemp's Ridley is a critically endangered species of sea turtle. They are the smallest sea turtle species, growing less than a meter long and averaging only 45 kilograms (100 lb) as an adult. Their range includes the Atlantic Ocean and the Gulf of Mexico. Almost all females return each year to a single beach - Rancho Nuevo in the Mexican state of Tamaulipas - to lay their eggs. In the past their numbers were severely depleted through hunting, but today major threats include loss of habitat, pollution, and entanglement in fishing (shrimping) nets. These turtles are called Kemp's Ridley because Richard Kemp (of Key West) was the first to send in a specimen of the species to Samuel Garman at Harvard.

Kemp's Ridley sea turtles are nicknamed the "Heartbreak Turtle" because when they died on deck of boats they would lie on their backs so fishermen would say that it died of a broken heart.

Carapace

Relatively short and wide, almost circular (wider in adults than that of L. olivacea); modest marginal serration or scalloping; high vertebral projections in juveniles, but carapace smooth and low in adults; carapace scutes slightly overlapping in immatures, and non-overlapping in adults; five pairs of costal scutes; straight carapace length (SCL) to 72cm.

Head

relatively large, subtriangular with convex sides; width to 13 cm; two pairs of prefrontal scales. Limbs: two claws on each flipper (some adults may lose the secondary claw on the front flippers).

Coloration

Dorsally grey in immatures, light olive-green in adults; underside white in immatures, yellow in adults.

Plastron

A distinct, small pore near rear margin of each of the four inframarginal scutes.

Distribution

Gulf of Mexico, eastern USA, occasionally western Europe.

Weight

Typically 35-50 kg. (Pritchard and Mortimer, 1999)

The nesting season for these turtles is between April to June, though some nest as late as July or August. They nest mostly in the Mexican state of Tamaulipas, but they sometimes on Padre Island in the U.S state of Texas. The adult sea turtles mate offshore and when a powerful wind blows from the north the females land in groups on the beach (they prefer areas with dunes followed by swamps). They are the only species of sea turtle known to lay their eggs during the day.

Females nest three times during a season with roughly 10 to 28 days between nestings. Incubation can take anywhere from 45 to 70 days. There are, on average, around 110 eggs per nesting.

On its head it has a "beak" of sorts used to grab and break up crabs on which it prefers to feed. (2006 IUCN Red List of Threatened Species.)

This specie do not occur in Costa Rica.

Flat back (Natator depressus) » Top

The Flatback Turtle is found in Australia. It is the only member of the genus Natator. The species may feed in the waters off Indonesia and Papua New Guinea, but it nests only in Australia. Nesting occurs across the top half of Australia, from Exmouth in Western Australia to Mon Repos in Queensland. The most significant breeding site is Crab Island in the western Torres Strait. Breeding may also occur on the islands of the southern Great Barrier Reef, and on mainland beaches and offshore islands north of Gladstone.

The Flatback turtle is unusual because it lays fewer, but larger eggs than the other sea turtle species. Females emerge onto the beach on which they hatched more than 30 years ago and make their way up the beach to lay their eggs. Females will lay a clutch of eggs around every 16-17 days during the nesting season, but will only nest every 2-3 years.

The Flatback Turtle eats algae, marine invertebrates and fish. (2006 IUCN Red List of Threatened Species.) Carapace: very broad and rounded, with upturned lateral margins; four pairs of costal scutes; scutes very thin and with a softer texture than in other cheloniid turtles, with seams often disappearing in old adults; curved carapace length (CCL) to about 100 cm. The caparace of the adult is on average 90 cm long.

The Flatback Turtle eats algae, marine invertebrates and fish. (2006 IUCN Red List of Threatened Species.)

Carapace

Very broad and rounded, with upturned lateral margins; four pairs of costal scutes; scutes very thin and with a softer texture than in other cheloniid turtles, with seams often disappearing in old adults; curved carapace length (CCL) to about 100 cm. The caparace of the adult is on average 90 cm long.

Head

Wide, broad, flat and subtriangular in shape; width to 13 cm in adults; three pairs of postorbital scales; one pair of prefrontal scales.

Limbs

Large scales present only on the edges of the front flippers, with most of the flipper covered by wrinkled skin or very fine scales; single claw on each flipper.

Coloration

Dorsally uniform olive-green in hatchlings and adults; yellowish ventrally.

Distribution

Confined to waters of tropical Australia and possibly southern New Guinea.

Weight

To about 90 kg. (Pritchard and Mortimer, 1999)

This specie do not occur in Costa Rica.