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 tumours, 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 tumours-forming disease Fibropapillomatosis, which is clearly a major problem for sea turtles.
The study, published this week in the journal Peer J, found that nitrogen runoff is ending up in algae that sea turtles eat, which is causing the tumours to grow both internally and externally on their eyes and flippers. According to NOAA, these tumours can interfere with their ability to eat and other essential behaviours, while tumours 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 Ridley's jaws are adapted for crushing and grinding Their diet consists primarily of crabs, mollusk's, 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 scissor like 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 (spine like 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 Ridley's 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 population 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 nocturnal 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 highest 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 interfere 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 kilometres (1 kilometre = 0.62 miles).
- Kemp's Ridley Turtles follow two major routes in the Gulf of Mexico; one northward to the Mississippi area, the other southward to the Campeche Bank, near the Yucatan Peninsula.
- Populations of Olive Ridley's 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 north-eastern 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 south-eastern 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 Ridley's 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 probably only 115,000 adult female Leatherbacks worldwide. There are too few records to predict trends.
Facts About Turtles
Turtles are reptiles of the order Testudines (all living turtles belong to the crown group Chelonian), most of whose body is shielded by a special bony or cartilaginous shell developed from their ribs. The order Testudines includes both extant (living) and extinct species. The earliest known turtles date from 215 million years ago, making turtles one of the oldest reptile groups and a more ancient group than lizards and snakes. About 300 species are alive today and most are highly endangered.
Turtles cannot breathe in water, but they can hold their breath for various periods of time.
Like other reptiles, turtles are "cold blooded" (or poikilothermic "of varying temperature"). Like other amniotes (reptiles, dinosaurs, birds and mammals), they breathe air and do not lay eggs underwater, although many species live in or around water. The largest turtles are aquatic.
The largest chelonian is the Great Leatherback sea turtle, which reaches a shell length of 200 cm (80 inches) and can reach a weight of over 900 kg (2000 lb or 1 short ton). Freshwater turtles are generally smaller, but with the largest species, the Asian softshell turtle (Pelochelys Cantorii, a few individuals have been reported up to 200 cm (80 inches). This dwarfs even the better known Alligator Snapping Turtle, the largest chelonian in North America, which attains a shell length of up to 80 cm (31 inches) and a weight of about 60 kg (170 lb).
Giant tortoises of the genera Geochelone, Meiolania and others were relatively widely distributed around the world into prehistoric times and are known to have existed in North and South America, Australia and Africa. They became extinct at the same time as the appearance of man and it is assumed that humans hunted them for food. The only surviving giant tortoises are on the Seychelles and Galapagos Islands and can grow to over 130 cm (50 inches) in length and weigh about 300 kg (670 lb).
The largest ever chelonian was Archelon Ischyros, a Late Cretaceous sea turtle known to have been up to 4.6m (15 ft) long.
The smallest turtle is the Speckled Padloper Tortoise of South Africa. It measures no more than 8 cm (3 inches) in length and weighs about 140 kg (5 oz). Two other species of small turtles are the American mud turtles and musk turtles that live in an area that ranges from Canada to South America. The shell length of many species in this group is less than 13 cm (5 inches) in length.
Neck
Turtles are broken down into two groups, according to how they evolved a solution to the problem of withdrawing their neck into their shell (something the ancestral Proganochelys could not do): the Cryptodira, which can draw their neck in while contracting it under their spine; and the Pleurodira, which contract their neck to the side.
Head
Most turtles that spend most of their life on land have their eyes looking down at objects in front of them. Some aquatic turtles, such as snapping turtles and soft shelled turtles, have eyes closer to the top of the head. These species of turtles can hide from predators in shallow water where they lie entirely submerged except for their eyes and nostrils. Sea turtles possess glands near their eyes that produce salty tears that rid their body of excess salt taken in from the water they drink.
Turtles are thought to have exceptional night vision due to the unusually large number of rod cells in their retinas. Turtles have colour vision with a wealth of cone subtypes with sensitivities ranging from the near Ultraviolet (UVA) to Red. Some land turtles have very poor pursuit movement abilities, which are normally reserved for predators that hunt quick moving prey, but carnivorous turtles are able to move their heads quickly to snap.
Turtles have a rigid beak. Turtles use their jaws to cut and chew food. Instead of teeth, the upper and lower jaws of the turtle are covered by horny ridges. Carnivorous turtles usually have knife sharp ridges for slicing through their prey. Herbivorous turtles have serrated edged ridges that help them cut through tough plants. Turtles use their tongues to swallow food, but they cannot, unlike most reptiles, stick out their tongues to catch food.
Shell
The upper shell of the turtle is called the Carapace. The lower shell that encases the belly is called the Plastron. The carapace and plastron are joined together on the turtle's sides by bony structures called Bridges. The inner layer of a turtle's shell is made up of about 60 bones that includes portions of the backbone and the ribs, meaning the turtle cannot crawl out of its shell. In most turtles, the outer layer of the shell is covered by horny scales called Scutes that are part of its outer skin, or epidermis. Scutes are made up of a fibrous protein called Keratin that also makes up the scales of other reptiles. These scutes overlap the seams between the shell bones and add strength to the shell. Some turtles do not have horny scutes. For example, the Leatherback sea turtle and the Soft shelled turtles have shells covered with leathery skin instead.
The shape of the shell gives helpful clues to how the turtle lives. Most tortoises have a large dome shaped shell that makes it difficult for predators to crush the shell between their jaws. One of the few exceptions is the African pancake tortoise which has a flat, flexible shell that allows it to hide in rock crevices. Most aquatic turtles have flat, streamlined shells which aid in swimming and diving. American snapping turtles and musk turtles have small, cross shaped plastrons that give them more efficient leg movement for walking along the bottom of ponds and streams.
The colour of a turtle's shell may vary. Shells are commonly coloured brown, black or olive green. In some species, shells may have red, orange, yellow or grey markings and these markings are often spots, lines, or irregular blotches. One of the most colourful turtles is the eastern Painted Turtle which includes a yellow plastron and a black or olive shell with red markings around the rim.
Tortoises, being land based, have rather heavy shells. In contrast, aquatic and soft shelled turtles have lighter shells that help them avoid sinking in water and swim faster with more agility. These lighter shells have large spaces called fontanelles between the shell bones. The shell of a Leatherback turtle is extremely light because they lack scute's and contain many fontanelles.
Skin and Moulting
As mentioned above, the outer layer of the shell is part of the skin, each scute (or plate) on the shell corresponding to a single modified scale. The remainder of the skin is composed of skin with much smaller scales, similar to the skin of other reptiles. Turtles and terrapins do not moult their skins all in one go, as snakes do, but continuously, in small pieces. When kept in aquaria, small sheets of dead skin can be seen in the water (often appearing to be a tin piece of plastic) having been sloughed off when the animal deliberately rubs itself against a piece of wood or stone. Tortoises also shed skin, but a lot of dead skin is allowed to accumulate into thick knobs and plates that provide protection to parts of the body outside the shell.
By counting the rings formed by the stack of smaller, older scutes on top of the larger, newer ones, it is possible to estimate the age of a turtle, if you know how many scutes are produced in a year. This method is not very accurate, partly because growth rate is not constant, but also because some of the scutes eventually fall away from the shell.
Limbs
Terrestrial tortoises have short, sturdy feet. Tortoises are famous for moving slowly, in part because of their heavy, cumbersome shell but also because of the relatively inefficient sprawling gait that they have, with the legs being bent, as with lizards rather than being straight and directly under the body, as is the case with mammals.
The amphibious turtles normally have limbs similar to those of tortoises except that the feet are webbed and often have long claws. These turtles swim using all four feet in a way similar to the dog paddle, with the feet on the left and right side of the body alternately providing thrust. Large turtles tend to swim less than smaller ones and the very big species, such as Alligator Snapping turtles, hardly swim at all, preferring to simply walk along the bottom of the river or lake. As well as webbed feed, turtles also have very long claws, used to help them clamber onto riverbanks and floating logs, upon which they like to bask. Male turtles tend to have particularly long claws and these appear to be used to stimulate the female while mating. While most turtles have webbed feet, some, such as the Pig Nosed Turtle, have true flippers, with the digits being fused into paddles and the claws being relatively small. These species swim in the same way as sea turtles.
Sea turtles are almost entirely aquatic and have flippers instead of feet. Sea turtles "fly" through the water, using the up and down motion of the front flippers to generate thrust; the back feet are not used for propulsion but may be used as rudders for steering. Compared with freshwater turtles, sea turtles have very limited mobility on land and apart from the dash from the nest to the sea as hatchlings, male sea turtles normally never leave the sea. Females must come back onto land to lay eggs. They move very slowly and laboriously, dragging themselves forwards with their flippers.
Life History
Although many turtles spend large amounts of their lives underwater, all turtles and tortoises breathe air and must surface at regular intervals to refill their lungs. They can also spend much of their lives on dry land. Aquatic respiration in Australian freshwater turtles is currently being studied. Some species have large cloacal cavities that are lined with many finger like projections. These projections, called "Papillae", have a rich blood supply and increase the surface area of the cloaca. The turtles can take up dissolved oxygen from the water using these papillae, in much the same way that fish use gills to respire.
Turtles lay eggs, like other reptiles, which are slightly soft and leathery. The eggs of the largest species are spherical, while the eggs of the rest are elongated. Their albumen is white and contains a different protein than bird eggs, such that it will not coagulate when cooked. Turtle eggs prepared to eat consist mainly of yolk. In some species, temperature determines whether an egg develops into a male or female: a higher temperature causes a female, a lower temperature causes a male. Large numbers of eggs are deposited in holes dug into mud or sand. They are then covered and left to incubate by themselves. When the turtles hatch, they squirm their way to the surface and head toward the water. There are no known species in which the mother cares for the young.
Sea turtles lay their eggs on dry, sandy beaches. Immature sea turtles are not cared for by the adults. Turtles can take many years to reach breeding age and in many cases breed every few years rather than annually.
Researchers have recently discovered a turtle's organs do not gradually break down or become less efficient over time, unlike most other animals. It was found that the liver, lungs and kidneys of a centenarian turtle are virtually indistinguishable from those of its immature counterpart. This has inspired genetic researchers to begin examining the turtle genome for longevity genes.
Turtles are divided into three suborders, one of which, the Paracryptodira, is extinct. The two extant suborders are the Cryptodira and the Pleurodira. The Cryptodira is the larger of the two groups and includes all the marine turtles, the terrestrial tortoises and many of the freshwater turtles. The Pleurodira are sometimes known as the side necked turtles, a reference to the way they withdraw their heads into their shells. The smaller group consists primarily of various freshwater turtles.
Evolutionary History
The first proto-turtles are believed to have existed in the early Triassic Period of the Mesozoic era, about 200 million years ago and their shell, which has remained a remarkably stable body plan, is thought to have evolved from rows of protective armour plates that gradually fused to one another and eventually to the reptile's ribs and vertebrae as well, creating a complete shell that offered protection at every stage of its evolution. By the late Jurassic, turtles had radiated widely and their fossil history becomes easier to read.
Their exact ancestry is disputed. It was believed that they are the only surviving branch of the ancient clade Anapsida, which includes groups such as procolophonids, millerettids, protorothyrids and pareiasaurs. All anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygomatic arch). The millerettids, proterotheriids and Pareiasaurus became extinct in the late Permian period and the procolophonid's during the Triassic.
However, it was recently suggested that the anapsid-like turtle skull may be due to reversion rather than to anapsid descent. More recent phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria. All molecular studies have strongly upheld this new phylogeny, though some place turtles closer to Archosauria. Reanalysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this classification (most of them studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa broadly enough for constructing the cladogram. As of 2003, the consensus is the Testudines diverged from other diapsids between 200 and 279 million years ago.
The earliest known fully shelled turtle is the late Triassic Proganochelys, though this species already had many advanced turtle traits and thus probably had many millions of years of preceding "turtle" evolution and species in its ancestry. It did lack the ability to pull its head into its shell (and it had a long neck) and had a long, spiked tail ending in a club, implying an ancestry occupying a similar niche to the ankylosaurs (though only through parallel evolution).
Turtle, Tortoise or Terrapin?
Although the word "turtle" is widely used to describe all members of the order Testudines, it is also common to see certain members described as terrapins, tortoises or sea turtles as well. Precisely how these alternative names are used, it at all, depends on the type of English being used.
- British English normally describes these reptiles as turtles if they live in the sea; terrapins if they live in fresh or brackish water; or tortoises if they live on land. However, there are exceptions to this where American or Australian common names are in wide use, as with the Fly River turtle.
- American English tends to use the word turtle for all freshwater species, as well as for certain land-dwelling species (box turtles). Oceanic species are usually referred to as sea turtles and tortoise is resticted to members of the "true" tortoise family, Testudinidae. The name "terrapin" is typically reserved only for the brackish water diamondback terrapin, Malaclemys terrapin; the word terrapin being derived from the Algonquian word for this animal.
- Australian English uses turtle for both the marine and freshwater species but tortoise for the terrestrial species.
To avoid confusion, the word chelonian is popular among veterinarians, scientists and conservationists working with these animals as a catch all name for any member of the order Testudines.
Turtles are killed and eaten and used for food, unnecessarily
The flesh of turtles was, or still is, considered a delicacy in a number of cultures. Turtle soup has been a prized dish in Anglo-American cuisine and still remains so in some parts of the Far East.
Guiling Gao jelly was a Chinese medicine preparation containing powdered shell of a certain turtle species; these days, though, it is typically made with only herbal ingredients.
"Harvesting" wild turtles is legal in Florida and a single seafood company in Fort Lauderdale was reported (2008) as buying about 5000 pounds of softshell turtles a week. The "harvesters" (hunters) are paid about $2 a pound; some manage to catch as many as 30-40 turtles (500 pounds) on a good day. Some of the catch gets to the local restaurants, while most of it is exported to the Far East; Florida Fish & Wildlife Conservation Commission estimates (2008) that around 3000 pounds of softshell turtles are exported each week via Tampa International Airport.
Rising Demand For Turtles In China
A rising demand in China for turtles for food and medicine has led to the round up of thousands of turtles from Florida's lakes, ponds and canals.
"Asian countries are causing the near extinction or extinction of every species of turtle they have over there, so now they're turning to the United States to supply their insatiable demand for turtle," said Matt Aresco, a turtle biologist from the Panhandle.
The trend which biologists worry about threatens the species survival.
Alabama and Texas, amongst other states, have recently restricted or banned the harvest of turtles and these states have cut off access, now the harvesters (turtle thieves) have focused more and more on Florida's turtles.
The so called harvesters (turtle thieves) target the larger turtles, the ones old enough to reproduce. Wipe out these and soon all turtles will be gone.
Special Information on Atlantic Green Turtles
Green Sea Turtles are listed as threatened or endangered throughout their habitat.
The Green Sea Turtle is found world wide in warm ocean waters.
A gentle vegetarian, feeding mainly on sea grasses and algae.
The most valuable of all reptiles, they are killed for their skins, calipee, meat and shells.
Exploitation has already caused extinction of populations in Bermuda and the Cayman Islands.
In parts of Florida (Indian River) more that 50% of the Green Sea Turtles are afflicted with fibropapilloma tumors.
The largest of the hard shelled marine turtles: common adult weight of 150 kg anjd length of over 100 cm.
Hatchlings: 4 to 5 cm in length.
Green Sea Turtles that nest at Ascension Island forage along the coast of Brazil and so must make a migration of 1000 km to reach their nesting site!
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