Sea Turtles

Endangered Sea Turtles Are Getting Deadly Tumors, and We’re to Blame


In sad news for sea turtles, scientists have found that runoff from cities and farms in Hawaii is causing debilitating and deadly tumors, which are believed to be the leading known cause of death for endangered green sea turtles.


Scientists from Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration (NOAA) teamed up to study what’s causing the tumor-forming disease Fibropapillomatosis, which is clearly a major problem for sea turtles.


The study, published this week in the journal PeerJ, found that nitrogen runoff is ending up in algae that sea turtles eat, which is causing the tumors to grow both internally and externally on their eyes and flippers. According to NOAA, these tumors can interfere with their ability to eat and other essential behaviors, while tumors on their eyes can cause permanent blindness. While it’s a major problem for green turtles in Hawaii, it’s also been found in other places and in other species of sea turtles, including loggerhead, olive ridley and flatback turtles.


Sea Turtles may be Carnivorous (meat eating), Herbivorous (plant eating) or Omnivorous (eating both meat & plants). The jaw structure of many species indicates their diet.

  • Green and Black Sea Turtles have finely serrated jaws adapted for a vegetarian diet of sea grasses and algae. In adult hood they are the only herbivorous sea turtles, but in an aquarium environment all sea turtle species can be maintained on a carnivorous diet.
  • Loggerheads and Ridleys jaws are adapted for crushing and grinding Their diet consists primarily of crabs, mollusks, shrimps, jellyfish and vegetation.
  • A Hawksbill has a narrow head with jaws meeting at an acute angle, adapted for getting food from crevices in coral reefs. They eat sponges, tunicates, shrimps and squids.
  • Leatherbacks have delicate scissorlike jaws that would be damaged by anything other than their normal diet of jellyfish, tunicates and other soft bodied animals. The mouth cavity and throat are lined with Papillae (spinelike projections) pointed backward to help them swallow soft foods.

Researchers continue to study the feeding habits of Flatbacks. There is evidence that they are opportunistic feeders that eat seaweeds, cuttlefish and sea cucumbers.


Some species change eating habits as they age. For instance, Green Sea Turtles are mainly carnivorous from hatchling until juvenile size; they then progressively shift to a herbivorous diet.

Human Impact


Nesting areas are becoming scarce due to beach development and disturbances. Kemp's ridleys only nest on one beach in the entire world: on a remote beach in Mexico near the village of Rancho Nuevo (about 161 km or 100 miles south of the Texas border). In 1947 scientists witnessed an arribada of more than 40,000 Kemp's ridley turtles in one day. In the 1960s numbers were reduced to less than 5000 turtles. In 1973 the largest arribada contained only 200 individuals.


Although the populatio of olive ridley sea turtles is the most in the world, their major nesting beach at Gahirmatha in Orissa, India is in jeopardy. The Government of India is planning to develop a major fishing port and processing plant 10 km (6.2 miles) from the critical nesting beach. More sea turtles nest on this beach than on any other beach in the world.


Nesting females and hatchlings are disturbed by the presence of rubbish on nesting beaches. Pollution impedes its crawl up the beach, a female returns to the sea instead of nesting.


The noise and activity of people on the beach may also cause females to return to the sea instead of nesting.

Some sea turtles die when they ingest rubbish. Leatherbacks are especially susceptible to ingesting plastic, mistaking it for jellyfish.


Thousands of sea turtles drown in shrimp nets each year. Sea turtles forage in waters where commercial shrimpers trawl. In 1947, 5000 US shrimping trawlers worked in the Gulf of Mexico. That number increased to 15000 full time and 40,000 part time trawlers by 1989.


Artificial lighting on beaches may misrepresent the time of day to turtles attempting to nest. Most turtles are noctural nesters and to a turtle that has not yet come ashore to nest, a brightly lite beach may signify daylight and inhibit nesting.


Hatchlings can become disoriented by city and street lights when trying to find the surf. Many young turtles actually head away from the ocean and toward parking lots. These animals may be eaten by predators or crushed by cars. Some die from exposure.


Some people illegally collect turtle eggs for food and for their alleged aphrodisiac effect.


Sea turtles are hunted illegally for their meat and shells, which are used to make combs, eyeglass frames, aphrodisiacs and curious. The fat of Green sea turtles, boiled with cartilage called Calipee, make a popular soup, which led to the decline in Green sea turtle population numbers.


Deforestation may indirectly threaten sea turtle nests. Costa Rica has one of the high

est deforestation rates in the world. Some researchers fear that without the forest to draw up ground water, the water table will rise beneath the beaches and drown nests.


Propeller and collision injuries from boats are not uncommon. These types of injuries are more frequent in areas with a high level of recreational boating, such as South Florida, the Florida Keys and the United States Virgin Islands.


Legal Protection For Sea Turtles


All eight species of sea turtles are listed as threatened or endangered on the US Endangered and Threatened Wildlife and Plants list. It is illegal to harm, or in any way interfer with a sea turtle or its eggs.


The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITIES) is an international treaty developed in 1973 to regulate trade in certain wildlife species. CITIES protects all species of sea turtles. The US and 115 other countries have banned the import or export of sea turtle products.


Turtle Excluder Device


At a cost of millions of dollars, the National Marine Fisheries Service developed the Turtle Excluder Device (TED).


The TED is a small, metal grid trapdoor inside a trawling net that allows shrimps to pass to the back, while the turtles escape to safety before becoming entrapped or entangled. 


Since 1989, federal law required this device to be installed on all the nets of all US fishing trawlers, working in areas populated by sea turtles.


Protecting Nests


Nests can be protected from predators by placing screens over them. Eggs laid too close to the water or in erosion zones can be relocated to safer areas.


Wildlife Refuges


Legislation is underway to allocate government funding for the Archie Carr National Wildlife Refuge on the east coast of Florida, between Melbourne Beach and Vero Beach. Full protection of the refuge would cost a total of $90 million dollars, of which $50 million dollars would come from state and local sources. As of 1994, federal funding has reached $7 million.

  • This 33 km (20.5 mile) section of beach is the most important nesting site for loggerheads in the Western Hemisphere.
  • The refuge is the most important nesting beach in the United States for the Green sea turtle.
  • The refuge also is considered prime real estate for commercial development, making government funding essential to its preservation.

The governments of Nicaragua and Costa Rica have established and are striving to expand, national parks and biological reserves where sea turtles forage and nest. Tortuguero, Costa Rica maintains the largest Green sea turtle rookery in the Caribbean. Local economics is no longer based on turtle harvests, but on tourism. More than 15,000 visitors are expected each year.


Sea turtles are found in warm temperate seas throughout the world.


Adults of most species are found in shallow, coastal waters, bays, lagoons and estuaries. Some also venture into the open sea. Juveniles of some species may be found in bays and estuaries, as well as at sea.


Migration habits differ not only among species but also among different populations of the same species. Some sea turtle populations nest and feed in the same general areas; other migrate great distances.

  • Green Sea Turtle populations migrate primarily along the coasts from nesting to feeding grounds,. However, some populations will travel 2,094 km (1,300 miles) across the Atlantic Ocean from the Ascension Island nesting grounds to the Brazilian coast feeding grounds.
  • Black Sea Turtles migrate along the coast from breeding areas to feeding grounds between the northern and southern extremes of their distribution range.
  • Loggerheads leave foraging areas and travel on breeding migrations that range from a few to thousands of kilometers (1 kilometer = 0.62 miles).
  • Kemp's Ridley Turtles follow two major routes in the Gulf of Mexico; one northward to the Mississipi area, the other southward to the Campeche Bank, near the Yucatan Peninsula.
  • Populations of Olive Ridleys have been observed in large flotillas traveling between feeding and nesting grounds in the Eastern Pacific and Indian Oceans.
  • Hawksbill migration studies have been limited. Evidence suggests that some Hawksbill populations show cyclic nesting migrations. Other researchers have documented nonmigratory and short distance migratory populations.
  • Flatbacks move from their nesting grounds on the northern coast of Australia and islands to feeding grounds in shallow waters of northeastern Australia. Distance covered ranges from 214 to 1,300 km (134 to 807 miles).
  • Leatherbacks have the longest migration of all sea turtles. They have been found more than 4,831 km (3000 miles) from their nesting beaches.

Total population figures are often unknown because juvenile and male sea turtles do not come ashore and are difficult to count.

  • The Kemp's Ridley is the most endangered sea turtle. In 1947, 92,000 nests were estimated. The numbers have been declining dramatically since then. Surveys conducted between 1978 and 1988 indicated an average of about 800 nests per year. Since 1978, the threat shows the number of nests have been declining at about 14 nests per year. The total number of nesting females may be as low as 350 on beaches where tens of thousands of Kemp's Ridley used to nest.
  • Nesting populations of Green and Black Sea Turtles have not been surveyed long enough for determination of trends. However, qualitative observations during visits over several years suggest a heavy decline.
  • The major Loggerhead nesting grounds are located in the southeastern US population trends of Loggerheads show a decline in nesting areas of Georgia and South Carolina, but no decline or a possible increase in southern Florida Atlantic areas. More years of nesting data and population biology studies are needed to assess the Florida trends.
  • The Olive Ridley, is the most, in the world. In 1991, an estimated 610,000 turtles nested in a single week on a beach in India. Now the Olive Ridleys are in decline.
  • Very little data is available on the Hawksbill populations. Estimation of population sizes of nesting females is difficult by aerial assessment: tracks in the sand do not last long and are difficult to see and nests are often obscured by beach vegetation.
  • Current population numbers for Flatback Turtles are not known; however, because of its restricted distribution, the Flatback is the most vulnerable of all sea turtles to any habitat change or over exploitation.
  • There are propbably only 115,000 adult female Leatherbacks worldwide. There are too few records to predict trends.

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