The wild sea turtles of the Cayman Islands

A green-loggerhead turtle hybrid

Hatchlings at the Turtle Farm.

by Lilian Hayball-Clarke of UCCI

Tuesday,  September 6, 2005

There are several different species of wild sea turtles which are diminishing, and their reproductive habits are changing due to the changing nature of their nesting beaches around Cayman. 

Sea turtles are reptilian vertebrates classified in the Order Chelonia. Numerous since the Jurrassic Period over 2 million years ago, sea turtles survived the age of dinosaurs by adapting to a marine life, leaving the sea only to nest on the hot wet beaches of tropical continents and islands. Scientists, naturalists, people young and old who love turtles are helping to save the green turtle and other species from extinction. There are four sea turtle species that regularly visit Cayman reefs: the green, loggerhead, hawksbill and leatherback turtles. Turtles have an important place in the culture of the Cayman Islands, stretching back the full two million years since these islands emerged from the Caribbean Sea.

The green turtle, sometimes known as the edible turtle, is one of the seven worldwide species of marine turtle alive today. It gets its name from the green colour of its body fat considered tasty and nutritious.

Its smooth olive-brown shell or carapace is heart shaped and can reach up to five or six feet long.

Instead of teeth, its serrated beak is notched like the edge of a saw, to help it graze as a herbivore on turtle grass and other marine plants inhabiting the coral reefs around our shores. Green sea turtles in the eastern Pacific Ocean are called black sea turtles, although some scientists consider the black sea turtle a separate species. 

Tortoise shell house-hold items and jewellery were once fashioned from the overlapping scales of the mature Green sea turtle’s shell. Polished and cut into various shapes to craft ear-rings, necklaces, serviette rings, spoons and small dishes, real turtle shell was coveted because it was beautiful. To save the slaughter of turtles for these products, synthetic ‘tortoise shell’ is now produced for crafting, being virtually indistinguishable from the real thing.

The most abundant of all the marine turtles, named for its massive head with jaws for crushing mollusc and crustacean shells, the red-brown loggerhead sea turtle cruises the outer reefs feeding on fish, jellyfish, mussels, clams, squid, shrimp, seaweed, and marine grasses. These handsome creatures reach 4- 5 feet in length and weigh up to 400 - 500 pounds. They often acquire barnacles and seaweed growing on their shells. Loggerheads travel widely and has been found as far as 500 miles (offshore).

In many areas of the world, this turtle is still hunted for its meat and eggs. They once nested throughout the tropics and as far north as Maryland in the US. Although they are still quite numerous, their nesting range has diminished as man has invaded coastal areas for housing and recreation. Attempts by the Cayman Department of the Environment and local residents to patrol beaches to protect nesting females and hatchlings are paying off. As with all sea turtles, loggerheads are long lived, estimates of their life expectancy range up to 60 - 75 years or more. 

Severely persecuted for “tortoiseshell”, the Hawksbill derives its name from the hooked beak formed by its yellowish jaws. It is the only sea turtle with overlapping carapace scales; they have two pairs of prefrontal plates between the eyes. The adult’s keeled shell is amber with streaks of red-brown, black-brown, or yellow. 

The underside is whitish-yellow, occasionally with black spots. Adult females range from 24-38 inches in length and weigh 60-190 pounds. The life span of this species of sea turtle is unknown.

Named for its birdlike beak, the hawksbill turtle usually nests near its sponge and coral feeding grounds and mates in shallow water off the nesting beach. Eretmochelys imbricata is medium-sized with a shield-shaped carapace. Hawksbills climb over reefs and rocks to nest among the roots of vegetation on beaches. Because of its shy nature and reluctance to breed on disturbed beaches, it is classified as critically endangered. 

The largest of all sea turtles, Dermochelys coriacea the leatherback turtle can grow to over 7 feet.

It just has a leathery back covering, unlike the shells of other turtles. These tireless swimmers have been found throughout the world’s oceans, as far north as Newfoundland and as far south as the southern coast of Chile. It is classified by the International Union for the Conservation of Nature (IUCN) as critically endangered.

You might also swim with other species of sea turtle around these islands such as the Kemp’s Ridley turtle, also called the Atlantic ridley, which is rare here and the world’s most endangered sea turtle. Very little is known of its habits. It is known that between April and mid-August, these turtles nest in only one place in the world, in large groups or arribadas. 

The Pacific or olive ridley, is a small sea turtle that has paddlelike flippers and grows up to 28 inches long, and hardly ever seen in Caribbean waters, as it inhabits oceanic tropical and subtropical waters of the Pacific, Indian and Atlantic. 

Its body is deeper than the very similar Kemp’s Ridley sea turtle with a length of 2 to 2.5 feet (62-70 cm). Its head is quite small with powerful jaws that can crack open the body armour of crustaceans such as shrimp and crabs, crush mollusks shells, snap up tunicates, and chew on fish. They typically forage off shore in surface waters or dive to depths of 500 feet (150 m) to feed on seabottom animals. Olive ridleys nest every year in arribadas, twice each season. An average of over 105 eggs are deposited in each nest. An average clutch size used to be over 110 eggs which required a 52 to 58 day incubation period. 

Eggs incubate for about 55 days. A speedy nester, it spends only about forty-five minutes on the beach laying its eggs.

The Department of the Environment Research Officers regularly walk the beaches of all three Cayman Islands between May and October to document the activities of nesting sea turtles. Volunteers join them and keep a round-the-clock vigil at any nests they find. Sea turtles migrate thousands of miles between their regular nesting beaches and their ocean feeding grounds. Starting in 2003 sea turtles that have been found nesting on Cayman’s beaches have been fitted with satellite transmitters to track their migrations. Documentation appears on the host website Seaturtle.org

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