Elusive Creatures of the Sea
by Claudia Colli
For the cruising yachtsman, spotting a sea turtle can be a thrilling sight. The distinctive head poking out of the water like a periscope, the silhouetted shape of its shell skimming just beneath the surface. Then with barely a ripple, this magical creature slips beneath the water and glides out of sight.
Ungainly on land, lissome in the water, marine turtles are fascinating, elusive, and increasingly endangered. The most common turtles to be found here are the hawksbill at around 150 pounds and the heftier green turtle at about double the weight. The impressive leatherback – a gentle giant of the sea at 1,400 pounds or more – is a temporary visitor who comes here to nest. And although each type of turtle has its distinctive characteristics, they have much in common. They swim beneath the water with ease, but being a reptile, must surface to breathe at regular intervals. They have evolved a streamlined shell, strong flippers and salt excreting glands which have helped them adapt well to their marine environment. Making the most of these traits, turtles can migrate great distances, and a turtle that starts its life in Africa may be seen here in the Caribbean – certainly a long distance swimming record of Olympian proportions. Although sea turtles spend most of their time in the water, they come onto land to lay their eggs. Turtles nest on beaches throughout the B.V.I. wherever the conditions are right. On Tortola, they prefer the soft sand of beaches like Josiah's, Trunk and Lambert Bays and a female will often return to the same beach or a nearby one to lay her eggs. Using her back flippers like scoops, this awkward creature is a proficient nest builder, and she will dig a tidy hole and bury her clutch of eggs with surprising dexterity. Interestingly, the warmth of this nest will determine, the hatchling's sex: eggs incubated at a warmer temperature produce mainly females and those at a lower temperature produce primarily males.
Unfortunately the odds are against a young turtle reaching maturity. In recent decades the number of sea turtles has been declining, and humans are largely to blame. Up until recently, turtle meat was a popular dish on local menus and its oil has been used for remedies from asthma to the common cold. The hawksbill's carapace, which has overlapping scutes (the hard, bony plates that constitute the shell) is unique among sea turtles, and it is this turtle's subtly hued amber, yellow and brown shell that has made it so sought after for jewellery. Development has also been a culprit in the decline of sea turtle populations. It has led to the loss of prime beach nesting sites, and lights from houses and nearby roads distract young hatchlings causing them to scurry towards the land rather than to the sea.
Spotting a turtle when out on the water may be a thrill for yachtsmen and snorkellers, but for others, locating and studying these unique creatures is a profession. Among those hoping to learn more about the area's sea turtle population, and ultimately reverse their decline, is a group of scientists and conservationists from the B.V.I. Department of Conservation and Fisheries, as well as the Darwin Initiative, an international programme dedicated to preserving diversity among plant and animal species around the world.
"Not a lot is known about sea turtles," admits Dr. Andy McGowan, a lanky Scotsman, who is working with the Darwin Initiative. Dr. McGowan hopes to change this by concentrating his studies on Anegada, where the green turtle and the hawksbill come close to shore in order to feed on the reef, making observation easier. There are potentially thousands of turtles in the waters off Anegada, he believes.
To study the turtles, Dr. McGowan and his team – which includes, Anegada resident Jim White, National Parks warden Rondell Smith and Anegada fisherman Damon Wheatley – first have to catch them. Once a turtle is caught, the team takes blood and tissue samples, and then tags it so it can be tracked long-term. Tagging can offer a rich mine of information from migratory routes to population numbers to age. DNA from tissue samples can show similarities in genotypes – like the turtle that Dr. McGowan found off Anegada whose DNA matched that of ones from Africa. Impressively a female will return to her home in Africa to nest.
Tagging turtles is trickier for Shannon Gore, who along with a team from the B.V.I. Department of Conservation and Fisheries, is studying sea turtles off the deeper waters off Tortola. These large creatures are unwieldy (a green turtle can be over three feet in length) and getting one into the boat without injury requires skill.
"Someone has to be towed behind the boat, and when he sees the turtle, he dives down and grabs it," explains Shannon, the department's marine biologist who makes this cumbersome task seem deceptively easy. Once the turtle is caught, Shannon, like Andy, measures and weighs it and takes a tissue sample in a quick and painless procedure. A small metal ID tag is clipped onto its flipper and for further identification, a microchip is inserted with a hypodermic needle. Both the tag and the chip will ensure that this turtle can be identified by other researchers however far afield it travels.
Working along with Shannon are Conservation staff members, Gary Frett, Ken Pemberton, Arlington Pickering, Sam Davies, and boat captain Henry Varlack, all of whom have become expert in the art of turtle catching. So far the Tortola team has tagged dozens of hawksbill and green turtles. More have been tagged on Anegada.
The Department also monitors beaches for nesting activities which requires a lot of late nights for Conservation staff. Leatherbacks for instance come onto local beaches to make nests between March and June and often not until one or two in the morning. Each successful nest can contain 90 to 100 eggs. In 1993 nine nests were recorded in the B.V.I. and in 2003 there were 65, indicating optimistically that leatherback numbers may be increasing here slowly. Andy McGowan is also monitoring turtle nesting sites and hatching success on Anegada.
One high tech way of monitoring turtle movements is through the use of satellite transmitters. Recently, Conservation and Fisheries staff attached a harness with a transmitter to a leatherback nesting on the beach at Lambert Bay. This is an expensive technology that has been difficult to implement. The transmitter is delicate and easily lost, but the information it can provide, which includes not only the turtle's location, but how fast, how often and how deep it dives, can shed further light on the movements of these elusive animals.
What will these studies accomplish? Because sea turtles are largely solitary and spend much of their time in deep ocean waters, studying them has been a challenge. But as time goes on research here in the British Virgin Islands will yield information about turtles world-wide. For instance, Dr. McGowan believes that information gleaned from tagging turtles here will help clarify why some areas have decreasing nesting numbers and others are increasing or are stable. The researchers are also looking at turtle growth rates – how long it takes a turtle to become an adult and how long it takes for it to reach reproductive size. Researchers aren't even sure about their longevity. Giant tortoises on the Galapagos live up to 150 years, and Dr. McGowan feels that sea turtles may also have very long life spans.
Turtles are an important part of the marine ecosystem. The leatherback, for instance, is a jelly fish predator. Jelly fish feed on fish larvae and without the leatherback keeping the number of jelly fish in check, fish populations might be reduced. Green turtles in turn, feed on sea grasses and algae. By grazing on seagrass blades and keeping them trim, the seagrass beds become more productive and more efficient nurseries for young fish.
Inevitably, better research will lead to better preservation strategies. Sea turtles are vulnerable in so many ways. By learning more about them, we will better know how to protect this magical creature of the sea.