marine turtles in the wild -...

2000 – A WWF SPECIES STATUS REPORT

2Executive Summary

4Turtles through Time

6Natural History of Turtles

14Threats and Issues

20What WWF has done for Marine Turtles

28What WWF is doing for Marine Turtles

38What Needs to be Done

by Elizabeth Kemf, Brian Groombridge, Alberto Abreu, and Alison Wilson

Marine Turtles in the Wild

The material and the geographical designations in this report do not imply the expression of any opinion whatsoever on the part of WWF concerning the legal status of any country, territory, or area, or concerning the delimitation of its frontiers or boundaries.

About the authors:Elizabeth Kemf is Species Conservation Information Manager for WWF International and

co-author and editor of WWF's species status reports.

Brian Groombridge is Compiler and Co-editor of the 1996/IUCN Red List of Threatened Animals, Species Survival Commission.

Alberto Abreu is Chairman of the IUCN/SSC Marine Turtle Specialist Group.

Alison Wilson is a biologist and independent science writer and a frequent contributor toand co-author of WWF's species status reports.

Conservation Editor: Marydele Donnelly, Programme Officer of the IUCN/SSC Marine Turtle Specialist Group.

Designed and produced by: Saatchi & Saatchi Advertising.

Published April 2000 by WWF – World Wide Fund For Nature (formerly World Wildlife Fund), Gland, Switzerland.Any reproduction in full or in part of this publication must mention the title and credit the above-mentioned publisher as the copyright owner.

© text 2000 WWF. All rights reserved.

EXECUTIVE SUMMARY

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xecutive summary

Marine turtles are fascinating creatures that have lived onthe earth for over 100 million years. Some early fossilrecords date back 230 million years. This remarkable reptile,of which there are seven species, is revered in culture andcustom around the globe. It symbolises longevity, fertility,strength and protection from harm. From the Aboriginalpeople of Australia and their neighbours in Asia and thePacific to coastal communities of Africa, Central, SouthAmerica and Europe, the turtle has held a place of specialimportance. In some creation myths it is believed to be theanimal on whose back the world was created.

The largest ever turtle, Archelon ischyros, lived duringthe Cretaceous Period, over 65 million years ago, andreached around 3.5m in length. Evidence from archaeolog-ical excavations shows that turtles were hunted by humanslong before written records were kept. Today, the largestturtle is the leatherback and one of the largest living reptiles.Leatherbacks grow to impressive sizes, up to 180 cm longand weigh about 500 kg. The largest leatherback everrecorded, an enormous male that stranded on a beach inWales, UK in 1988, was 256 cm in length and weighed nearly a ton.

Turtles have always attracted attention, whether layingtheir eggs on beaches or hatching from shells and making amad dash to the surf in the first minutes of life. Scuba divers,snorkellers and lucky swimmers who glimpse them bychance underwater thrill to the sight. No matter how idol-ized the turtle may have been, or still is, it has been exploitedfor centuries as a source of food, decoration and commerce.Because of overuse and other threats – including pollution,accidental drowning in fishing nets or hooking by longlinefishing and habitat loss – six of the world’s seven marine turtles are in danger of extinction. The hawksbill and Kemp’s ridley have been classified by the IUCN/SSCMarine Turtle Specialist Group as “Critically Endangered”.All seven species are listed on Appendix I of the Conventionon International Trade in Endangered Species of WildFauna and Flora (CITES), thus prohibiting internationaltrade in them by more than 140 CITES member nations.

Decorative tortoiseshell, from the carapace of thehawksbill turtle, has been traded over long distances since atleast the time of the pharaohs, and certain Red Sea portsflourished on the basis of this trade. Some say that Cleo-patra’s bathtub was fabricated from tortoiseshell. (Parsons1972) They were also a prominent feature of the earliestknown coins, referred to as “turtles” in the slang of the day,minted in the Greek state of Aegina from 700 BC onwards.

Demand for tortoiseshell remains high, especially inJapan and other parts of East and South and Southeast Asia,and two countries, Cuba and Dominica, have proposed thatthe international trade in the hawksbill turtle be reopened.WWF opposes the resumption of trafficking in this and the other six species of marine turtles. Many populations

that were abundant 100 to 200 years ago are now depleted,declining or remnants of their former size. Local extinctionshave occurred in all ocean basins, and no population, noteven those that are stable as a result of long-term conser-vation and management, is completely safe. Numbers ofnesting marine turtles (of four species) in Malaysia havefallen drastically in recent decades, with leatherback nestsdeclining by 98 per cent since the 1950s.

After the shrimp trawl fishery was identified as a majorsource of mortality in the early 1980s, net inserts or TurtleExcluder Devices (TEDs) were developed to allowentrapped turtles (and other bycatch) to escape. AlthoughTEDs are used widely in the western hemisphere, they arenot employed extensively in shrimp and other trawl fisheriesaround the world. Mortality in longline fisheries for pelagicspecies such as swordfish and tuna is also a grave andincreasing threat. These fisheries, which set billions of hookseach year, continue to expand. Marine turtles swallow long-line hooks or becomeentangled in lines anddrown. Many animals thatare released alive, but withhooks embedded in theirbodies, usually die. Marineturtles are also captured anddrowned in various gill net fish-eries and in the lines of fish traps.Programmes to reduce mortalitythrough modified gear and fishingtechniques, or closing particular areasat particular times, are needed; fish-ermen should be encouraged to assist in these efforts.

In recent years powerful new tools, such asgenetic analysis and satellite telemetry, have beendeveloped to answer the riddles surroundingmarine turtles, but much remains to be discov-ered, and much needs to be done.

Marine turtle conservation requirementsshould be included in coastal zonemanagement plans as well as eco-system conservation programmes.Regulations for maintaining waterquality and contingency plans foroil and chemical spills are critical tomaintain the health and produc-tivity of the ecosystems on whichmarine turtle depend. The threatsposed by dynamite fishing, marinedebris, and oil pollution should be eliminated. Where necessary,legislation must be encouraged,such as lighting restrictions on nest-

ing beaches. Erosion, accretion, sand mining, and foot andvehicular traffic also need to be addressed on nestingbeaches to ensure that nesting females, eggs and hatchlingsare protected. Long-term monitoring programmes are alsocritical to assessing the impact on these habitats.

For many populations of marine turtles around theworld, the day-to-day support of local coastal communitiesis crucial to their survival. In some areas the turtle is a valu-able source of nourishment and ecotourism income. If themarine or sea turtle vanishes, the world will lose not only along-treasured symbol, it will also witness the disappearanceof a species that has roamed the earth for hundreds of millions of years.

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EXECUTIVE SUMMARY

Green turtle hatchling. Upon leaving the nest, green,hawksbill and loggerhead turtles rush to the surf andthen to the open ocean wherethey spend several yearsbefore returning to their“home” beach.

2000 WWF Species Status Report 3

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urtles throughtime

History and CultureThe symbol of the turtle is universally revered in culture andcustom around the world. It represents longevity, fertility,strength and protection from harm. From the aboriginalpeople of Australia to the coastal communities of Africa,such as the Bajuni people of Kenya, the turtle holds animportant place in their lives. In some creation myths it isbelieved to be the animal on whose back the world was cre-ated. For example, among the Hurons and the Iroquois ofNorth America, the “Legend of the Woman Who Fell Fromthe Sky” describes how the earth was formed. A womanlived in the upper world before the earth was formed.“There was nothing but water, nothing but a wide, wide sea.The only people in the world were the animals that lived inand on water. Then down from the sky a woman fell, a divineperson.”(Clark 1979) The legend varies as to which birds,ducks or loons, flew beneath her, catching her as she plungedinto the darkness and saved her from drowning. But all vari-ations of this myth say that it was the Great Turtle whoasked that she be placed on his back. Around his back earthwas placed, where plants and trees could grow, “and it is yettoday that the Great Turtle still bears the earth on his back”. (Ibid)

Among Hindus, the second incarnation of the godVishnu was as a turtle. After a great flood, various gods triedto raise the earth. Vishnu transformed himself into a turtle

and upon his back he lifted up the earth and saved it fromthe powerful waters. (Pritchard 1990) In Hindu

belief, the tortoise or turtle supports the elephant,which in turn supports the earth. Temples and

shrines all over the world honour all kinds ofturtles, those that live in the sea and in freshwater, as well as tortoises that live on land.The turtle in India has long been consideredas holy, while in neighbouring Bangladeshthere is a Muslim temple where the custom of caring for the turtles has survived for centuries. In the city of Chittagong, people

worship and look after the black three-clawedsoftshell turtle, a species of freshwater turtle

found nowhere else in the world (Pritchard 1990). Astone tablet recently discovered in Taiwan, dated 1883,

tells a story of how 18 wealthy philanthropists worked together in the Chin Dynasty to protect baby girls, old cattleand sea turtles.

The first known turtles are represented by fossil material from the Late Triassic Epoch, some 230 millionyears old. These ancient forms already show most of the distinctive features of shell and skeleton characteristic of turtles, and so the evolutionary affinities of the group arequite obscure. Marine turtles, possibly descendants ofspecies that inhabited swamps and marshes during the LateTriassic Epoch, evolved into their present familiar form

TURTLES THROUGH TIME

Ancient Greek coins like this replica wereused as money and known then as “turtles”. Now it is the symbol of the SeaTurtle Protection Society of Greece.

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approximately 110 million years ago and have wandered theplanet’s oceans ever since. The largest ever turtle, Archelonischyros, lived during the Cretaceous Period, over 65 millionyears ago, and reached around 3.5 m in length. Evidencefrom archaeological excavations shows that turtles werehunted by humans long before written records were kept.

In the tropical Pacific Islands the hawksbill is still con-sidered sacred and in the Gilbert Islands turtles are used asfamily totems. (Witzel 1983) According to the Mayas ofCentral America, the God of the Moon is protected by abreastplate of tortoiseshell. The nearby Tolteca people callthe celestial Shield of Orion, Thoh, which also means turtlein their language. (Devaux 1991) Further north in theUnited States, a more recent type of turtle reverence andrespect has sprung up. Thousands of people have joined tur-tle and tortoise clubs, whose members can follow the fate ofthese much loved ancient creatures not only in the oceansbut also in newsletters and websites on the Internet.

However worshipped the turtle may have been or stillis, it was also exploited as a source of food, decoration andcommerce. Decorative tortoiseshell, from the carapace ofthe hawksbill turtle, has been traded over long distancessince at least the time of the Pharaohs, and certain Red Sea

ports flourished on the basis of this trade. In Nubia andEgypt, many ancient graves have been found containingornaments fashioned from the carapace of turtles, known astortoiseshell. The English language term originates becauseof the sea turtle shell’s similarity to the carapace of land tortoises. Spanish (carey) and French (caret, écaille) wordsare believed to originate from the language of the Arawakpeoples of the West Indies. (Parsons 1972)

Some say that Cleopatra’s bathtub was fabricated fromtortoiseshell. (Parsons 1972) Rome and India presented giftsmade from tortoiseshell to the Chinese Emperor. In Palau,tortoiseshell from the hawksbill turtle was used for ceremo-nial “women’s money” (Witzell 1983). Turtles were also aprominent feature of the earliest known coins, referred to as“turtles” in the slang of the day, minted in the Greek state ofAegina from 700 BC onwards.

By the 19th century international displays of tortoise-shell products were held in the UK, France, and the US. In1852, manufacturing of combs for women’s hair was mostsignificant in Scotland and the State of Massachusetts in the US. “Tortoiseshell, a 19th century British periodicalobserved, was imported from more countries than any sim-ilar material.” (Parsons 1972) Today, all seven species ofmarine or sea turtles are listed on Appendix I of CITES, thus prohibiting trade in them by those countries who areCITES member nations. However, demand for tortoiseshellremains high, especially in Japan and other parts of East,South and Southeast Asia. Accidental killing in longline fishing and nets, continued trade, combined with over-consumption of turtle meat and eggs for subsistence, commercial, and even ceremonial purposes, are threateningthis living legend with extinction.

TURTLES THROUGH TIME

Marine turtle in Bali being prepared for ceremonial sacrifice. WWF isworking with spiritual and community leaders to find alternatives.

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NATURAL HISTORY OF TURTLES

aturalhistory

of turtles

There are relatively few marine reptiles of which sea turtlesare by far the most familiar. Others include sea snakes (the largest group, containing about 50 species), a marineiguana and one or two crocodilians that range into brackishor coastal marine waters. There are seven living species ofmarine turtle although the actual status of the east Pacificgreen or black turtle remains uncertain. Arguments for andagainst its designation as an eighth species are the subject of ongoing debate. The family Dermochelyidae includes the single species Dermochelys coriacea, the leatherback turtle. The other six are placed in the family Cheloniidae: (1) Caretta caretta, the loggerhead turtle, (2) Cheloniamydas, the green turtle, (3) Eretmochelys imbricata, thehawksbill turtle, (4) Lepidochelys kempii, Kemp’s ridley turtle, (5) Lepidochelys olivacea, the olive ridley turtle, and(6) Natator depressus, the flatback turtle. Although sometaxonomists have named and described marine turtle subspecies, largely on the basis of colour and body propor-tion, these names are not in common use. There is now lessinterest in morphological characteristics than in patterns of genetic differentiation.

Five of the seven speciesare found around the globe(mainly in tropical and sub-tropical waters) while twospecies have relatively restrict-ed ranges: Kemp’s ridley occursmainly in the Gulf of Mexicoand the flatback turtle aroundnorthern Australia and southern

New Guinea. Most species spendmuch of their lives in continental

shelf waters, although leatherbackand olive ridley turtles tend to lead

more of their lives on the high seas.Males do not leave the sea and femalesonly come ashore to lay their eggs on

sandy beaches during the appropriateseason. The first several years of lifeare spent drifting in the open ocean,with most time thereafter in coastalfeeding grounds.

During the nesting season,mature males and females migrate from

feeding grounds and mate near the nesting beach. Femalesmate with several males and store the sperm for repeatedfertilisation of eggs without the need for further mating.

A female turtle typically crawls out of the water and upthe beach at night to lay many eggs, often more than 100, ina single nest, returning to the water before dawn. On undis-turbed beaches, she may repeat this process several moretimes in a single nesting season, but will then spend the nexttwo years or so on the feeding grounds preparing for another

Loggerhead turtle.

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nesting migration. In the case of Lepidochelys species (the two ridley turtles), huge numbers of turtles (sometimesmany thousands) may clamber ashore together over a period of several days, a phenomenon known as anarribada (arrival).

During a given season, an individual nesting female maylay all her clutches within the same few square metres, show-ing high nest-site fidelity. Even more remarkably, femaleshave a strong tendency to return to nest on the same beachon which they were hatched (high philopatry) as evidencedby the fact that individual nesting aggregations tend to showdistinctive types of mitochondrial DNA, which is passed onfrom mother to daughter in cell cytoplasm. This differenti-ation suggests that there is relatively low female gene flowbetween nesting colonies.

The fact that another type of DNA (contained in cellnuclei) does not vary in the same way suggests that there issome exchange of genetic material between colonies. Thiscould be explained if males tend to mate with females fromdifferent populations. An assumption that males are theprincipal source of genetic exchange between colonies couldbe explained if newly mature males are more interested infinding a female with which to mate, than in the location ofthe beach to which the pair eventually migrates. Feedingareas are used by turtles from different populations, so sucha mechanism is feasible.

Although there is a rapidly growing body of genetic evi-dence, its interpretation is not always straightforward, as notall marine turtles in all oceans share this basic pattern.Leatherbacks, for example, colonise new beaches as theyappear in some areas of the tropics and researchers havedocumented the use of adjacent beaches by individual greenturtles in the waters of Australia. However, the key practical

implication of this new information is that nesting coloniesrequire conservation management on an individual basis. Adepleted nesting population will not be replenished byfemales from another population. Genetic evidence has alsodemonstrated that feeding areas contain turtles from morethan one nesting population and not necessarily just fromthe nearest nesting beach. This means that people in onecountry might easily be harvesting turtles hatched in one ormore other countries, which serves to highlight the need forinternational cooperation on turtle management.

Turtle researchers monitoring a nesting beach near Karachi, Pakistan.

Turtle hunter with olive ridley.

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low indeed, while the worth of an adult or large subadult isextremely high. In this situation, the loss of a small propor-tion of egg output from a beach is unlikely to have severeconsequences. At the other extreme, the practice of directlyharvesting nesting females from a beach is likely to haveenormous impact on the population.

Humans take turtles principally for their meat, shells(carapace), and fat. Turtles are particularly vulnerable topredation by humans because of the ease with which theycan be captured. Collecting the eggs from a nest is as easy asdigging a hole and filling a bucket. Females are incrediblyvulnerable when they come ashore to nest and adults arereadily tracked by fishermen because they swim slowly, haveto come to the surface to breathe, and are highly visible fromboats as they swim through clear tropical waters. They areharpooned, netted or simply seized by divers.

Turtles have frequently been sighted far out to sea,sometimes travelling in large aggregations, and are capableof covering considerable distances. Studies in which turtleshave been tracked using satellite positioning technology

Hatchings The eggs are completely unprotected once the motherreturns to the sea. Eggs incubate for 55 to 75 days, depend-ing on the temperature. The size and weight of hatchlingscorrelate with egg size. Like many reptiles, the sex of thehatchling turtles is dependent on the temperature in thenests, with cooler temperatures favouring the developmentof males, and warmth favouring females.

Although successful hatching rates may reach 80 percent, there may be high predation, for example by mon-gooses, ghost crabs, rats, racoons, jackals, feral pigs anddogs, to mention just a few. In many parts of the world tur-tle eggs are prized by humans as a rich source of protein, andare often reputed to have aphrodisiac properties. Conse-quently all accessible nests may be stripped of their eggs. Inother cases, nests may be located below the high tide mark,resulting in the destruction of many clutches by seawater.

The hatchlings tunnel out of the nests usually, but notalways, at night. Aligning themselves with the main sourceof light, which in undisturbed situations will be the marinehorizon, they rush to the surf. At beaches altered by humandevelopment, artificial light often attracts hatchlings inland,where they are vulnerable to predators and road traffic, andin any case soon desiccate. Where people and turtles co-existalong developed beaches, shaded low-intensity yellow light-ing can much reduce this problem. During the frenzied dashto the water, hatchlings may suffer intense predation, espe-cially if emerging during the day. At this size they are of lim-ited interest to humans, but birds, mammals and crabs feaston this bonanza, with few hatchlings reaching the surf. Oncein the water, the hatchlings head towards the incomingwaves and out to sea, where they still face a high risk of pre-dation from birds and large fish such as groupers, snappersand barracudas.

The survivors disperse into pelagic waters and spendseveral years at sea. Some species do not return to coastalwaters until full sexual maturity, others do so as large juve-niles. This period at sea, which can last up to a decade, iscommonly referred to as the “lost years” and is the least wellunderstood part of any turtle species’ life history. Recently,however, some hatchlings have been tracked for consider-able periods of time. Presumably turtles are less vulnerableto predation by birds and some fish while in deeper waters.Once they have grown sufficiently large to avoid suchattacks, the turtles are really only consumed by sharks, killerwhales (occasionally) and, of course, humans.

The broad reproductive strategy of marine turtles is tospend a very long time developing to sexual maturity – per-haps 20 to 30 years on average, longer in cold nutrient-poorareas – and then devote enormous resources to producinglarge numbers of eggs several times during a nesting season.The worth of any individual egg or hatchling, in terms of itslikelihood of contributing to population persistence, is very

Leatherback hatchlings rushing to the surf in French Guyana.

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in areas of open sea, and there are relatively frequent obser-vations in temperate waters, and sometimes in brackishlagoons and estuaries.

Mating occurs in open water, and – unlike in otherspecies – often takes place some way from the shore. Themajor Atlantic nesting grounds are off the Coast of Floridaand South Carolina. Loggerheads are also the most commonturtle in the Mediterranean, with nesting reported fromGreece and Turkey to Israel, Tunisia, and Libya. NorthernNatal and Masirah Island, Oman, are the main nesting sitesin the Indian Ocean, and nesting occurs throughout South-east Asia to Australia, but rarely in the central and westernPacific islands. Females lay between 40 and 190 eggs perclutch (average is about 100) and larger females tend to laylarger eggs. The loggerhead is classified by the SSC MarineTurtle Specialist Group as “Endangered”

Green turtle (Chelonia mydas) So called because of the colour of the cartilage and fatdeposits around its internal organs, green turtles are darkblack-brown or greenish yellow. At up to 1.5m in length, thegreen turtle is the largest cheloniid turtle. Scientists note thatindividuals from Hawaii and the eastern Pacific are partic-ularly dark in colour, and sometimes call it the black turtle.The largest female green turtles are found in the Atlanticand western Pacific Ocean, less in the Indian Ocean and theCaribbean. The smallest is found in Guyana (80cm); weightranges between 90 and 200 kg. The carapace is oval whenviewed from above, and the head is relatively small andblunt. Green turtles are widely distributed in the tropics, par-ticularly near continental coasts and around islands, andhave been recorded in temperate waters. The only herbivo-rous marine turtle, the species feeds mainly on seagrasses,flowering plants which grow in shallow coastal waters,mainly in the tropics and subtropics. Females migrate hugedistances between the feeding grounds and nesting beaches.

Nesting occurs widely throughout the range, even on thecentral Pacific islands, where few other turtles now occur.Female green turtles sometimes show strong nest site fixity.An individual nests about once every three years, and laysbetween two to five clutches of 40 to 200 eggs, which developfor 50 to 70 days before hatching.

An estimated 100,000 green turtles are killed around theIndo-Australian archipelago each year. There is a near totalegg harvest in several countries, e.g. Thailand and Malaysia(although egg production in Sarawak dropped from 2,200,000 eggs in the mid-1930s to 175,000 in 1995) and disease threatens populations elsewhere. As a result, popu-lations are declining worldwide, with numbers in Indonesiadecreasing by tenfold since the 1940s, and by more than halfin French Polynesia. The SSC Marine Turtle SpecialistGroup has assessed this species as “Endangered”. Recoveryhas occurred under strong conservation management


have confirmed that they undertake enormous huge migra-tions, many thousands of kilometres, during their lives.Recently, a female turtle tracked by satellite across thePacific had travelled 7,000km before contact was lost. Manyfemales forage over large geographical areas yet return tothe same beach to nest, navigating by a series of cues.

FAMILY CHELONIIDAE

Loggerhead (Caretta caretta)Loggerheads are among the biggest cheloniid turtles, some-times measuring well over a metre in shell length, weighingup to 180kg, and having characteristically large heads andstrong jaws. They are carnivorous throughout their lives, eat-ing bottom-dwelling molluscs (conch, clams), crabs, urchinsand sponges, as well as free-swimming jellyfish. Loggerheadsare widely distributed in coastal tropical and subtropicalwaters, and travel large distances following major warm currents such as the Gulf Stream and California Current.Solitary adults and groups of juveniles may be encountered

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regimes, but only in a very few cases (e.g. Sabah TurtleIslands National Park in Malaysia and Florida USA).

Hawksbill (Eretmochelys imbricata)A medium-sized cheloniid that grows to about 90 cm inlength and weighs 60 kg on average, the hawksbill, as itsname suggests, has a narrow pointed beak reminiscent of abird of prey. The shell is highly coloured with elaborate pat-terns. The overlapping carapace scales are often streakedand marbled with amber, yellow or brown, most evidentwhen the shell material is worked and polished. The hawks-bill has a pan-tropical distribution and has only rarely beenrecorded away from the tropics. It is the sole source of com-mercial tortoiseshell.

Nesting occurs widely throughout the range, but tendsto be more dispersed than in other species. There are fewmajor nesting colonies and only five sites have populationswith more than 1,000 females nesting annually. The hawks-bill often nests on beaches close to coral reefs, and it is oneof the turtles most frequently encountered by scuba diversover coral reefs. Female hawksbills nest every two or threeyears, laying 60 to 200 eggs at a time. Sponges normally

constitute a major proportion of the diet. Hawksbill turtles are carnivorous and use their narrow beaks to extract invertebrate prey from reef crevices. Both sessile and mobileanimals are consumed.

Hawksbills have been hunted for centuries as a sourceof tortoiseshell (“carey”) for jewellery and ornaments. Inrecent decades eastern Asia, and Japan in particular, hasprovided an eager market for tortoiseshell. Through inter-national conventions and national legislation some countrieshave sought with considerable success to restrict trade.Japan was a major market for tortoiseshell until 1994. Cubahas, in 2000, put forward a proposal to CITES, together withDominica, to reopen international trade, with Cuba sellinghawksbill shell to Japan. Harvest for domestic trade stilloccurs in many countries, including Cuba, Dominica,Indonesia, the Solomon Islands and Fiji. Because of thestrong evidence of significant worldwide decline and on-going projected declines the hawksbill has been assessed bythe SSC Marine Turtle Specialist Group as “CriticallyEndangered”. WWF rejects reopening the internationaltrade in hawksbill shell or “tortoiseshell”.

Kemp’s ridley (Lepidochelys kempii) The two species in the genus Lepidochelys are the small-est of all marine turtles, reaching around 0.7m.

Kemp’s ridley has an almost completely roundcarapace and four pores on either side of the lower sur-face. These are openings to glands, which releasepheromones important in the timing of mass nesting.

TABLE 1. CONSERVATION STATUS OFMARINE TURTLES

Species/Common Name Status

Caretta caretta EN(loggerhead turtle)

Chelonia mydas EN(green turtle)

Eretmochelys imbricata CR(hawksbill turtle)

Lepidochelys kempii CR(Kemp’s ridley turtle)

Lepidochelys olivacea EN(olive ridley turtle)

Demachelys coriacea EN(leatherback turtle)

Natator depressus V(flatback turtle)

EN - EndangeredCR - Critically EndangeredV - Vulnerable

Source: IUCN/SSC Marine Turtle Specialist Group


Kemp’s ridley turtle has been classified as “Critically Endangered”.

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The Kemp’s ridley turtle, is restricted to the Gulf ofMexico and coastal waters of the western Atlantic Ocean ofthe United States. This species prefers shallow sandy andmuddy habitats, such as the coastal lagoons of Louisiana,Texas and Alabama; as a result, these turtles are usuallyobserved near to shore.

However it is neither size nor distribution that qualifiesKemp’s ridley as something of an oddity amongst turtles; itis its breeding behaviour. Nesting occurs conspicuously inbroad daylight, and apart from sporadic nesting elsewhere,takes place only on one 20 km beach at Rancho Nuevo inMexico on the Gulf of Mexico. In the past, tens of thousandsof females nested simultaneously at the beach, a true arribada. Nowadays arrivals are numbered in the hundreds.Females lay an average of 1.5 clutches of 100 eggs per season.

Kemp’s ridley turtles are carnivorous throughout theirlives, although the feeding behaviour of the hatchlings andjuveniles is very poorly understood. The adults consumecrabs, shrimps, clams and sea urchins and grow to 72 cm andweigh 35 to 50kg.

There was massive exploitation of eggs until this speciesreceived protection in 1965. The nesting population crashedfrom more than 40,000 turtles coming ashore in a single dayin the late 1940s to a few hundred females nesting in anentire season in the late 1980s. As a result of an enormousconservation effort to protect all nests produced at RanchoNuevo and required use of Turtle Excluder Devices (TEDs)to reduce capture in fishing nets, the species is undergoinga remarkable recovery. Because of documented decline,Kemp’s ridley has been assessed by the SSC Marine TurtleSpecialist Group as “Critically Endangered”.


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With its documented decline and the continuing pressure of incidental catch, beach development, and other factors,the olive ridley has been assessed by the SSC Marine TurtleSpecialist Group as “Endangered”.

Flatback turtle (Natator depressus)The flatback is a distinctive species, having a flat body andsmooth carapace with upturned edges. It has the most lim-ited range of any turtle species, being found only around thenorthern half of Australia, and in the seas between northernAustralia and southern parts of Indonesia and Papua NewGuinea. Flatbacks only very rarely leave the shallow watersof the continental shelf, and nest only in northern Australia,where beaches on small offshore islands are the most impor-tant sites. Nesting females coming ashore are sometimestaken by crocodiles, possibly their major natural predator.

Very little is known about diet during the early stages ofdevelopment, but the species is believed to be predomi-nantly carnivorous, with squid, sea cucumbers, soft corals,and molluscs all being recorded in stomachs. Females growto about 100cm and weigh about 90kg.

The restricted range means that the flatback isextremely vulnerable to habitat loss, especially of breedingsites, but the major threat appears to be incidental catch bythe numerous fishing vessels operating in waters favoured bythese turtles. The species is not particularly valued by indige-nous peoples and so is rarely subject to direct hunting; itscarnivorous diet is believed to be responsible for an unpleas-ant taste. Annual nesting populations range up to 10,000, butlong-term changes in this species are impossible to measure,

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Olive ridley (Lepidochelys olivacea) The olive ridley turtle looks very similar to Kemp’s ridley,but has a deeper body, with slightly upturned edges to thecarapace. It grows to about 72 cm, and weigh 35 to 50 kg.However, the two Lepidochelys species have very differentdistributions, with olive ridley absent from the Gulf of Mexico and Florida, but present throughout the Antilles, the north coast of South America, west Africa, the IndianOcean, Australia and Southeast Asia. Despite this wide distribution, the species has only been observed around con-tinents and large islands, where large flotillas are sometimesobserved moving between feeding and nesting grounds.

The main nesting beaches are on the eastern Pacificcoasts of Central America, from Mexico to Costa Rica, innortheastern India, and Suriname. Sometimes the beachesare separated from the mainland by coastal lagoons. In theseareas, thousands of females emerge from the sea and nestsimultaneously, over a period of two to three days. Thearribada is believed to be an adaptation against predation,the predators being overwhelmed by numbers, and one reason for the past success of this species. However, many ofthe beaches are relatively small, less than 10 km long, andnesting may be so dense that successive waves of femalesoften dig up previously laid nests in efforts to lay their owneggs. Mass arrivals can be repeated (two to seven times aseason) and each female lays an average of 1.5 clutches eachyear of nesting, of approximately 110 eggs, although this can vary considerably. The species is typified by its wide diet, consuming an enormous range of sessile and mobilemarine organisms.


Freshly-laid turtle eggs in danger of collection are sometimes but not always protected.

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as most populations have never been monitored. Thisspecies may be the least-threatened marine turtle, and hasbeen assessed as “Vulnerable” by the SSC Marine TurtleSpecialist Group.

FAMILY DERMOCHELYIDAE

Leatherback turtle (Dermochelys coriacea) The leatherback is the largest turtle and one of the largestliving reptiles. Leatherbacks grow to impressive sizes, up to 180 cm and weigh about 500 kg. However, the largestleatherback ever recorded, an enormous male which wasfound stranded on a beach in Wales in 1988, was 256cm longand weighed 916kg! Aside from their bulk, leatherbacks areeasily distinguished by their leathery-ridged carapace, lack-ing the horny plates (scutes) of other turtles. Leatherbacksalso have disproportionately long front flippers compared to other turtles – they are at least half the length of the carapace in adults.

This species has an unusually wide latitudinal range as adults are able to withstand cold (10 °C) water. Theleatherback has been recorded north to Alaska and south tothe Cape of Good Hope and occurs regularly in waters offNew England, in the Bay of Biscay and off southeast Aus-tralia. It is a highly pelagic species, venturing close to shoremainly during the nesting season, and is capable of diving toseveral hundred metres. Adults feed mainly on pelagic soft-bodied creatures such as jellyfish and tunicates, which occurin greatest concentrations at the surface in areas of upwellingor convergence (see p.15 sections on Pollution and Bycatch).

The regular appearance of leatherbacks in cool temperatewaters, e.g. in the northeast Atlantic, is probably due to theseasonal occurrence there of large numbers of jellyfish.

The most important nesting areas are on the westerncoasts of Mexico, Suriname and French Guyana, Malaysia,Irian Jaya (Indonesia), and western Sumatra (Indonesia).Female leatherbacks lay four to five times per season, eachtime depositing 60 to 120 eggs. Strangely, a relatively largeproportion of eggs in each clutch are small and without yolkand may serve as spacers for the nest.

The meat of this species is very oily and not particularlyfavoured for human consumption. Worldwide populationdeclines, coupled with continuing pressures of egg harvest,incidental catch and beach development have caused the leatherback to be assessed by the SSC Marine TurtleSpecialist Group as “Endangered”.


Olive ridley shells outside a formerslaughterhouse in Mexico.

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The Kemp’s ridley turtle was once the most common turtlein the Gulf of Mexico, yet now it is critically endangered.The extent and dramatic nature of this decline is evident in old film footage of the 1947 arribada in which an esti-mated 40,000 females came ashore to nest in a single night.Given that there may well have been two to three times this number of females which did not lay that evening, and perhaps an equal number of males far offshore, then the population 50 years ago numbered a few hundred thou-sand. In 1985, just 200 females nested on Rancho Nuevo. In recent years, Kemp’s ridley has been undergoing expo-nential recovery on the nesting beach after more than twodecades of protection and nearly ten years of Turtle Excluder Devices.

What pressures could have produced such a collapse inpopulation numbers? The following is a summary of theprincipal human impacts on turtle populations worldwide,though different species are more or less vulnerable to different pressures, in different locations.

Direct consumptionTurtles generally make good eating. Although the leather-back is less frequently consumed, and in some areas the fleshof other species is considered unpalatable (e.g. Kemp’s ridley turtles in Mexico) or even poisonous (e.g. hawksbillturtles in parts of the Indo-Pacific), there is a long history ofhuman consumption. The high yield of good quality meat,combined with the ease with which turtles can be caught, hasmade them particularly desirable food items in coastal com-munities around the world. The green turtle quickly becamea dietary staple of colonial mariners and plantation ownersin the Caribbean from the late 16th century onwards; esti-mates suggest that tens of thousands were consumed annu-ally in Grand Cayman, Jamaica and other parts of the WestIndies. As air-breathing animals, turtles can survive trans-portation by boat and overland, and they can also be kept in holding enclosures for some time. As a result, from the mid-18th century onwards turtle soup was produced in London from animals shipped from the Caribbean, and thisinternational trade continued (albeit at a much reducedscale) well into the 20th century. Green turtles in theMediterranean were almost extirpated by exploitation ofnesting females in the 1940s. Many other nesting populationsaround the world were heavily depleted as consumptionpressures increased in parallel with coastal development,human population increase, and breakdown of culturalrestraint on harvesting.

Turtle eggs are also easy to collect and highly nutritious.As a result, the arrival of nesting females is traditionallyregarded as a predictable bounty, providing a welcomechange of diet. This allure is further enhanced by the aphro-disiac properties, which are frequently attributed to turtleeggs, so much so that they are traded illegally.

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hreats and issues

THREATS AND ISSUES

Over collection of turtle eggs is threatening some marine turtle popula-tions with extinction.

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This problem is particularly acute because these two speciesfeed on planktonic organisms that are found in highest con-centrations along oceanic fronts, areas that also support thehighest densities of pelagic fish.

Habitat destruction and alterationThe construction of seawalls, hotels, marinas and the entireinfrastructure associated with coastal tourism and commercehave destroyed large areas of turtle nesting beaches aroundthe world. Turtle reproductive behaviour evolved in an envi-ronment of deserted, intact beaches. Nowadays, light andnoise pollution frequently deter or interrupt many femalesfrom successful laying. Hatchlings locate the water’s edge byorientating themselves towards the horizon, but house andstreet lights can disorient newly hatched turtles so that theyactually crawl away from the sea. Adult turtles are reportedas displaying symptoms of acute physiological stress in someareas of very heavy coastal traffic, such as the Adriatic. It ispossible that these adults may be deterred from comingashore at all.

PollutionHeavy metals including aluminium, arsenic, cadmium, cop-per, iron, mercury, selenium and zinc, have been recorded in the tissues of stranded turtles, especially the kidneys and

Turtles have also been hunted for their shells, which are used in jewellery, and their hides, which are cured forleather. There are recent reports of turtle-leather cowboyboots being freely available in Tijuana, Mexico, and ofrooms full of confiscated boots on the US border. Thoughtrade in marine turtles is illegal under CITES, they are stillstuffed, varnished, mounted and sold openly as tourist curiosin Vietnam, Cambodia, Mexico and parts of the Caribbean.

Bycatch and longline fishingAn unknown quantity (some estimates are as high as 200,000to 300,000 annually) of turtles are killed as “bycatch” (i.e. incidentally), particularly in trawling nets. Decline wasset in motion by decades of egg collecting and the killing offemales; then it was continued by trawler mortality. This isprobably one of the major causes of decline in the Kemp’sridley turtle which is particularly vulnerable because it feedsin the rich shrimping grounds of the Gulf of Mexico (see p.17section on Turtle and shrimp fishing). Longlines for tuna andswordfish are responsible for killing leatherback and log-gerhead turtles, which are attracted to the baited hooks. Theturtles either become snared or tangled in the line and arethen unable to reach the surface and drown (or in some caseslose a limb). Turtles that have swallowed hooks most certainly die as well, although they may be released alive.

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THREATS AND ISSUES

Loggerhead turtle drowned in fishing net.

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marine habitats are near areas of heavy human use and terrestrial runoff.

Tumours can blind the turtles or inhibit their ability tofeed. Tumours may also develop internally in the lungs, liver,kidney and gastrointestinal tract, resulting in flotation prob-lems, bowel obstruction, kidney failure and pressure necro-sis (death) of affected tissues. Affected turtles are generallyextremely emaciated, weak and anaemic, with severelyrestricted eyesight, and are likely to die prematurely. Since1983, 31 to 54 per cent of stranded green turtles in Hawaiihave been found to bear fibropapillomas. Although regres-sions of tumours have been reported recently, the prognosisfor most turtles with tumours is poor.

Although circumstantial evidence may suggest that pol-lutants could be a factor, studies have so far been unable tofind any unusual concentrations of pollutants in the afflictedpopulations. It is possible that the disease is the result of acombination of factors. Turtles under stress from pollutioncould be more vulnerable to a virus that would otherwise berelatively harmless.

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liver. These metals were measured in concentrations suffi-ciently elevated to cause metal toxicity. Similarly, phthalateesters, molecules used in the manufacture of plastics whichare known to be toxic and have mutagenic and carcinogenicproperties, have been identified in turtle eggs. The exacteffects of these and other substances on the reproductivebiology and health of turtles, and the implications for theirconservation, are unknown but surely negative.

There is no uncertainty as to the effects on turtles ofanother type of marine pollutant, solid debris. Items as var-ied as tar balls, condoms, fishing line, plastic bags and bottleshave been found in the stomachs of all species in quantitiesso great that normal nutrition must be impaired. Occasion-ally turtles make meals of spectacular objects such as the 3 x 4m heavy plastic sheet (found in a loggerhead), or the180m monofilament line consumed by a leatherback – offNew York, United States. Such nondegradable items persistin the ocean for years and if not eaten directly still pose adanger to turtles through entanglement, which at bestimpedes swimming and at worst leads to the loss of limbs,choking or drowning (as is the case with drift nets used incommercial fishing). The problem of ingestion of marinedebris and entanglement is particularly acute for new hatch-lings during the first few years after birth (the “lost years”).During this period they are pelagic, drifting with strongoceanic currents and inevitably they are concentrated alongfronts where there is an abundant supply of both shelter(sargassum weed) and pelagic prey. Scraps of plastic alsoaccumulate here and soon become encrusted with ediblebryozoans, barnacles and algae. This, and the fact that tarballs and styrofoam pellets are the same size and shape assargassum floats, probably account for the misguided feed-ing on these items by young turtles.

Disease Debilitating and disfiguring tumours have been identified in numerous populations of turtles in the late 1970s,although these abnormalities were first described in greenturtles in the 1930s. The prevalence of these tumours, calledfibropapillomas, which develop in a manner similar to wartsin humans, increased dramatically in the 1980s in Floridaand Hawaii where more than 50 per cent of some popu-lations were found to be affected. Widespread problemswith fibropapillomas are a new phenomenon. Reportsinvolving the capture, handling, and sighting of thousands of turtles by former turtle fishermen in Hawaii indicate that tumours were virtually non-existent prior to the 1950s.Although most commonly seen in Chelonia mydas (greenturtle), tumours have been found in loggerhead, olive ridley, flatback and leatherback turtles as well. Up to 92 per cent of individuals can be infected in some areas, withhighest prevalence in shallow near-shore waters with rela-tively restricted water turnover. Many (but not all) of these

THREATS AND ISSUES

Green turtle with life-threatening tumours.

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Turtles and shrimp fishingInstead of swimming away from an approaching net, turtlestry to outswim the trawl but get caught once they tire. Afteryears of studying this problem, the US National MarineFisheries Services developed Turtle Excluder Devices(TEDs) for use by commercial fishermen. TEDs are panelsof large mesh webbing or metal grids inserted as barriersinto the funnel–shaped shrimp nets. As the trawls aredragged along the bottom, shrimps and other small animalspass through the TED and into the narrow bag at the end ofthe funnel where the catch is collected. Sea turtles, sharks,and fish too large to get through the panel are deflected out an escape hatch (the TED), reducing bycatch by up to 97 per cent.

Without TEDs sea turtles become trapped in a net foras long as it is towed underwater and sometimes drown orundergo physiological changes that result in death. Prior tothe required use of TEDs in the US, tens of thousands of seaturtles drowned in shrimp nets each year.

Although shrimp fishermen feared TEDs would cost theshrimping industry millions of dollars in equipment and lost catch, TEDs have proved successful in the United Statesand elsewhere. They also reduce fuel costs by excluding non-shrimp species that often outweigh shrimps by ten to one and provide a better quality catch (the shrimps are not crushed by other species).

However, the US government’s requirement for the useof TEDs became one of the most bitterly fought regulationsin the history of fisheries management. Mexico and 13 otherCentral and South American nations followed this lead,mainly because under a 1989 law the US Department ofState banned the import of shrimps from any country nottaking adequate measures to conserve sea turtles in com-mercial shrimp fisheries. In 1988, 150,500 tonnes of shrimpsworth US$ 506 million were caught in US waters. The rest ofthe 365,500 tonnes consumed that year were imported,mainly from India, Indonesia, Thailand, Mexico, Malaysia,Korea and Japan, all nations where turtles are under serious threat.

Despite the benefits of using TEDs, some internationalopposition remains. In 1997 four Asian countries – Thailand,India, Malaysia and Pakistan – challenged the US decisionto ban shrimp imports from countries with inadequatemarine turtle conservation measures. The nations took thecase to a WTO dispute panel, which interprets WTO rules.While the WTO has the power to suspend free trade rulesfor conservation reasons, the panel ignored the relevantinternational conservation agreements including the Gen-eral Agreement on Tariffs and Trade (GATT) and ruledthat the US ban was illegal. After an appeal by the US, theWTO finally acknowledged the potential of such a traderestriction to protect the environment. However, it stilljudged the US action to be illegal, ruling in favour of freetrade. WWF believes that the WTO is failing to fulfil themandate contained in the preamble to its own charter: topromote trade that is environmentally responsible and thatencourages sustainable development.

Over-exploitation of eggs and adultsUnder natural conditions, turtles suffer high hatchling, post-hatchling and juvenile mortality, but those that survive theearly days grow into long-lived animals with delayed sexualmaturity and very low adult mortality. Unfortunately, con-ditions nowadays are far from “natural” and turtles suffermortality at all stages of their life cycle, leading to increas-ingly regular population crashes. In the days of Columbus, theCaribbean Sea was described as being “thick with them [greenturtles], and they were of the very largest, so numerous that itseemed that the ships would run aground”. This is a rare sighttoday. The number of female leatherbacks nesting on thePacific beaches of Mexico has declined tenfold in less than adecade; the number of nesting loggerheads in eastern Australia

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progressively depleted until there are no more recruits.These “last adults” will, in theory, survive for another 20years during which time the situation may not seem too seri-ous. In reality, however, the population is on the verge of extinction because once these adults die there will be no hatchlings, juveniles or sub-adults to replace them. Ifjuvenile and adults are being killed, e.g. as bycatch, then thiswill simply happen more quickly.

International Agreements for Turtle ConservationInternational trade in turtle products was formerly a majorcause of population depletion. Since all species of marineturtles were listed on Appendix I of CITES, trade betweenParty states has decreased. However, illegal trade and hunting for international markets outside theCITES framework remains of concern, andlocal consumption continues.

has declined by 50 to 80 per cent since the mid-1970s; Kemp’s ridley nearly went extinct. The list goes on, and makesdepressing reading. The causes are many and varied, but havetheir roots in two basic characteristics of turtle biology whichrender populations particularly vulnerable to the pressuresdescribed above.

Turtle populations can be destroyed from the “bottomup” by over-exploitation of the eggs, and destruction of nesting sites. For example, as far as we know, green turtlestake 30 to 50 years to reach sexual maturity and remainreproductive for about 20 years. Adults are the visible com-ponent of a turtle population; their numbers are maintainedby the gradual maturation of juvenile and sub-adult turtles.This will continue to happen, even if no eggs are laid or if all the eggs are collected. It will be many decades beforethe number of adults begins to decline,but over time the reservoirof juveniles and sub-adults will become

THREATS AND ISSUES

Turtle and products for sale in Vietnam.

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This group of species is ideally matched to the aimsexpressed by the Convention on the Conservation of Migra-tory Species of Wild Animals (also known as the Bonn Con-vention or CMS). The text of the CMS includes many of theconcepts fundamental to regional conservation of migratorymarine animals and their habitats. With the exception of theflatback (Natator depressus), all species of sea turtles arelisted in both Appendix I and Appendix II of the Bonn Convention. The Inter-American Convention for the Pro-tection and Conservation of Sea Turtles (IAC) is the onlymajor international treaty dedicated exclusively to sea turtles and their habitats, formally setting standards for

their conservation. The IAC recognizes that sea turtles

migrate and that they are resourcesshared by the peoples of many nations.

Hence, the IAC has been vigorously supported by many members of theinternational community of sea turtlebiologists and conservationists, particu-larly specialists from Latin America. Inorder to enter into force, eight countries

must ratify the agreement. Currently, 12States have signed and six have ratified. The

treaty is expected to go into force in 2000. The measures proposed in the IAC promote

regional management plans and accords. Its stated objective is “to promote the protection, conservation and recovery of sea turtle populations and of the habitats on

which they depend, based on the best available scientific evidence, taking into account the environmental, socio-economic and cultural characteristics of the Parties”. In the same vein, the Protocol concerning Specially ProtectedAreas and Wildlife (SPAW) to the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (known also as the Carta-gena Convention) is complementary to the IAC. All sixspecies of Caribbean sea turtle are listed in Annex II of the SPAW Protocol.

THREATS AND ISSUES

Turtles and turtle products for sale in a hotel lobby in Ho Chi Minh City.

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Since it was founded in 1961, WWF has supported numeroussea turtle conservation efforts worldwide. Much of the earlywork involved mapping the distribution of nesting beaches,with surveys in more than 40 countries. Other projectsfocused on survival of eggs and hatchlings, establishment of protected areas, research into sea turtle biology, ecology and behaviour, monitoring the trade in turtle products,investigating the threats from fisheries, and sponsoring international conferences and workshops on sea turtle conservation.

WWF assisted in the creation of what was to become theIUCN/SSC Marine Turtle Specialist Group (MTSG). “Thepresent world situation for the great marine turtles is tragic,”said a Statement issued after the First Working Meeting ofMarine Turtle Specialists organized by IUCN in 1969.Describing 20th-century population declines as “cata-strophic”, biologists called for a variety of conservation mea-sures, more public awareness campaigns, and internationalcooperation for turtle protection. WWF swung into actionimmediately, funding surveys throughout the 1970s along

the coasts of southern Africa, Australia and Latin America.In 1979, WWF supported the first World Conference on theConservation of Sea Turtles, and helped set in motion anAction Plan of 137 urgent projects. For WWF 1980 was the“Year of the Turtle”.

In the past 30 years, biologists have started to explorethe mysteries of turtle migrations by tagging adult andimmature turtles and more recently by using satellite tech-nology. From these studies, it has become apparent that

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hat WWF has

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WHAT WWF HAS DONE FOR MARINE TURTLES

Loggerhead turtles have been a focus of WWF’s conservation work in the Mediterranean, especially in Greece and Turkey.

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marine turtles in the wild -...

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