Sea turtles under pressure

30 October 2012 by Danny Haelewaters, posted in Marine biology

Costa Rica - It has been named the promised land of biodiversity, Mother of Ecotourism, and it also harbors one of the most important nesting sites for sea turtles. Five of the world’s seven species of sea turtles nest regularly on Costa Rica’s beaches. How spectacular and breathtaking is it to see a sea turtle crawl up onto the beach and nest? A highlight for sure for those chasing fascinating nature experiences, but be careful: these last members of prehistorical animal species are threatened. Seriously threatened.  

Sea turtles are endemic in tropical and subtropical waters but live more or less everywhere, except in the Arctic Ocean. Some species travel enormous distances each year; loggerhead sea turtles nest along Japan’s coastlines and then migrate to the Mexican coast for food. Leatherbacks can stand cold temperatures, which is why they can be observed from Alaska’s coasts in the north to the furthest tip of New Zealand in the south.

(Almost) always in the water: male versus female

Hence their name, sea turtles spend most of their time in the water. Female sea turtles come on the land to lay eggs during the nesting season. Some females have been studied and found to have stored sperm after mating and lay eggs even nine months later. Males do not usually come out of the water, but they do occasionally. Basking allows the sunlight to kill off any unwanted parasitic growth on their shell and skin. Leaving the water also protects them from sea predators such as sharks.

Fossil record brings the age of sea turtles at some 200 million years, yet currently these animals are not doing well.

For millions of years, sea turtles have lived in their free world. Although threatened by natural enemies such as bigger predator fish, sharks and whales, water birds and all kinds of land animals threatening both the eggs and hatchlings, they have continued to survive. However, during recent decades sea turtles are facing more dangerous threats:

  1. The water they live in has become more and more polluted with domestic waste, pesticides, PCBs, plastics, soil particles, dioxins, hormones, mercury, lead, cadmium, flame retardants, radioactive discharges, oil, persistent organic pollutants, phosphates, nitrates, and so on. The sea turtles confuse the non-degradable waste with their "normal" food sources and die by suffocation. The leatherback feeds off a diet predominantly of jellyfish and unfortunately many individuals die because of the consumption of plastic bags, which can very much resemble their favorite food in the water.
  2. Pollution and stress are the major causes of fibropapilloma disease. Tumors, particularly of the skin, induce difficulties in sight, swimming and feeding activity. Without any treatment, these problems will be fatal for the animal.
  3. Because of increasing coastal development around the world and especially in Costa Rica, the beaches where females lay their eggs are under great pressure. Costa Rica boasts some of the main beaches for five species of sea turtles. Therefore it is of utmost importance that these beaches will remain largely free from any form of tourism.
  4. Although prohibited by CITES, sea turtles are (illegally) traded for the consumption of meat, the use of the shells as decoration and the production of oil (mainly of leatherback turtles). Their eggs are also sold at shocking rates in some parts of the world for human consumption.
  5. Maybe the biggest ecological problem of our generation is that of the gigantic by-catches in commercial fisheries. Each year some 78 million tons of fish are taken from the sea, 40% of which is by-catch and consequently thrown overboard dead or wounded. Sea turtles are often the victims of unwanted catches; only taking into account the southeastern United States, the number of sea turtles that perish annually as by-catch is estimated 55,000. In Costa Rica, only 3% of what shrimping nets catch is shrimp – the other 97% are primarily sea turtles, sharks, manta rays, and dolphins.

Juvenile Hawksbill sea turtle (Eretmochelys imbricata ) | © Phoebe Edge

Little ones, fighting for their life

Sea turtles mate in open sea. Every one to two years, the female returns to the beach to lay some hundred eggs. A green sea turtle female, however, may return only once every six years. The female will almost always go back to the same beach, that of her own birth. Therefore it is important that Costa Rican beaches, crucial for the survival of sea turtles, remain as intact as possible.

Once at the beach, the female digs a hole and lays her eggs. After fulfilling these tasks she shuffles back to sea. There’s no maternal care with sea turtles.

Young hatchlings are very cute and not a threat to anyone. Their likelihood to survive, however, isn’t very high as they have so many predators. Research has shown that of one thousand newborns only a single one will survive. Immediately upon hatching they find their way towards the water, while simultaneously they have to fight to survive against predators: birds, crabs, lizards, white-nosed coatis, dogs ... and humans.

Baby sea turtles should never be taken by hand and put into the sea. It is critical that they take this route to the water themselves. Only during these first heroic shuffle moments, the setting of their “birth beach” can be registered, enabling them to retrieve this place during later on in life when it is time to return.

© Rhett A. Butler + Mongabay.com

Conservation project at the Península de Osa

The Osa is a peninsula in southwestern Costa Rica, to the Pacific Ocean. It is about the most biodiverse place of Costa Rica, witness the land’s oldest National Park Parque Nacional Corcovado that harbors more than half of all Costa Rican animal species. National Geographic even states: ‘the biologically most intense place on earth’.

Special about the Osa is that the four species of sea turtles nest along the merely 15 km coastline. Still, the situation is far from ideal for the sea turtles, because of the set of common threats (see above) and at the Osa in particular the specific tidal currents on these beaches; nests are often washed away at high tide.

COTORCO (Comité para la conservación de las Tortugas marinas de Corcovado – English: committee for the conservation of sea turtles of Corcovado) seeks to increase the number of sea turtles nesting on the Osa, and to prevent predation and poaching activities by means of an efficient and consistent education and conservation program for the local population. A hatchery has been constructed on Carate beach this year where eggs hatch under natural conditions in a protected environment.

Hatchery | © Phoebe Edge

As soon as the eggs have been laid, they are moved to the hatchery where they can be protected from the high levels of predation currently noted for Carate beach. When hatchlings leave the nest, they are carried in a bucket to the site where their mother initially laid the eggs, and make their way to the sea alone, as they would do naturally.

By daily patrols and permanent guarding of the hatchery, jobs are created for the community, the locals learn something about nature conservation, and the long-term survival of the four sea turtles species at the Osa is ensured. By giving presentations and selling T-shirts money is raised to ensure payments of the salaries for the local community members who work in the hatchery. Researchers involved in the project are able to conduct professional scientific research and to publish.

Both research reports and popular science articles are needed to ask for more attention for this intriguing yet often forgotten group of animals.

 

Thanks are due to Phoebe Edge for useful suggestions and to Rhett A. Butler for permission to share the above picture. For more information about COTORCO and options to volunteer, please contact: osaturtles[at]gmail.com.

__________________________________________________

The following five species of sea turtles occur in Costa Rica. The loggerhead sea turtle is only seen at Caribbean coasts. The four other species are species of the Península de Osa.

 Latin nameLengthWeightStatus
Leatherback sea turtleDermochelys coriacea165-190 cm400-500 kgCritically endangered
Green sea turtleChelonia mydas150 cm200 kgCritically endangered
Hawksbill sea turtleEretmochelys imbricata90-110 cm40-80 kgCritically endangered
Olive ridley sea turtleLepidochelys olivacae70-80 cm45-60 kgEndangered
Loggerhead sea turtleCaretta caretta90 cm (max. 270 cm)135 kg (max. 454 kg)Endangered

2 Responses to “Sea turtles under pressure”

  1. Mario Urpi Reply | Permalink

    Excellent! Thank you for the article, we plan to expand next year with everyone's help.
    That way we are going to have a larger area under protection.

  2. Rick B Reply | Permalink

    Great article and personal issue for me. I was a member of an Earthwatch team about 15 years ago, which I helped collect nesting and other data on the huge leatherbacks that come to the beaches in the Guanacaste province of Costa Rica. These animals desperately need some help, and sites like this are vital for spreading the word - thank you!

Leave a Reply


nine − = 8