Olive Ridley Turtle IUCN Status Category: Endangered
Lepidochelys olivacea (Eschscholtz 1829) CITES Appendix: I
The olive ridley looks very similar to the Kemp's ridley, but has a deeper body and slightly up-turned edges to its carapace. Olive ridleys grow to an average length of 70cm, and adults weigh approximately 45kg.
This species eats an enormous range of sessile and mobile marine organisms. It can dive to great depths, and at least one study suggests that it may be a bottom feeder. The olive ridley is migratory, often travelling thousands of kilometres between feeding and nesting sites. Despite a wide distribution, olive ridleys have only been observed around continents and large islands, where they sometimes occur in large flotillas.
Females reach sexual maturity at about 12 years of age. Many thousands of them emerge from the sea and nest simultaneously over a period of two to three days. These arribadas (a Spanish word meaning 'mass arrivals') are believed to be an adaptation against predation, the predators being overwhelmed by numbers, and one reason for the success of this species. However, olive ridleys often choose small, narrow beaches less than 10km in length, and nests may be so closely packed that subsequent waves of females often dig up other nests in their efforts to lay eggs. Nesting is seasonal, dependent on the location of the nesting beaches, and arribadas may be repeated two to seven times a season. Each female digs an average of two to four nests per year of nesting, laying approximately 100 eggs in each. Evidence suggests that the olive ridley nests at intervals of one, two, three, and four years). Ridley turtles typically camouflage their nests, compacting the sand over the nest by rocking laboriously from side to side.
The olive ridley has not been recorded around the Gulf of Mexico or Florida, but occurs through the Antilles, around the north coast of South America, in West Africa, the Indian Ocean, Australia and Southeast Asia. There are also many important nesting and feeding grounds on the east Pacific coast from as far north as Canada to as far south as southern Peru. Although it nests at low frequency throughout much of its range, some of the highest concentrations of the olive ridley are found on the coast of Orissa, India (principal beach is Gahirmatha), the Pacific coast of Costa Rica (principal beach is Nancite) and the coast of Oaxaca, Mexico (principal beach is La Escobilla).
Range States: Angola, Australia, Bangladesh, Brazil, Costa Rica, El Salvador, French Guiana, Guatemala, Guyana, Honduras, India, Indonesia, Kenya, Madagascar, Malaysia, Mexico, Mozambique, Myanmar, Nicaragua, Oman, Pakistan, Panama, Papua New Guinea, Peru, Senegal, South Africa, Sri Lanka, Suriname, Tanzania, Thailand, Trinidad and Tobago, Venezuela. [Atlantic (eastern central, southeast, southwest, western central), Indian Ocean (eastern, western), Pacific (eastern central, southeast, southwest, western central)]
World-wide numbers of these migratory animals are almost impossible to estimate. It is possible to estimate numbers of mature females on nesting beaches, but not all rookeries have been surveyed and on those that have, numbers may be inaccurate owing to uncertainty as to how many times an individual nests in a season. A recent estimate of 800,000+ olive ridley females has been made.
Major Breeding Population: Currently the largest breeding population is located on the coast of Orissa, India.
Olive ridley populations are in sharp decline due to a depressingly familiar list of causes including poaching of eggs, beach development, fishing, and pollution. The belief that turtle eggs have aphrodisiac properties is a major threat to olive ridley populations in Central and South America. The Galibi Nature Reserve, Suriname, hosted the largest and most important olive ridley nesting population in the western Atlantic. Thousands of females were nesting there in the 1960s, but local villagers were harvesting nearly all the eggs. Conservation efforts were resisted forcibly by the local villagers and ceased in 1989. In 1989, only about 450 females came ashore. A survey in 1995 counted just 335 olive ridley females nesting in this area. The illegal nature of the turtle egg trade makes it difficult to estimate the impact on olive ridley populations, but seizures of eggs are not uncommon. The largest on record occurred in October 1996 in Mexico City, when a lorry containing over 500,000 olive ridley eggs, taken from a single beach, was seized. The size of this haul indicates the demand for eggs in Central America and among the Hispanic communities of California and Florida.
Like the Kemp’s ridley turtle, the olive ridley will always be vulnerable, because such a large proportion of its reproductive effort is concentrated in only a few locations. Man-made or natural disturbances to nesting beaches can have huge repercussions on the whole population. For example, Hurricane Pauline destroyed nearly half a million nests, the equivalent of 40 million eggs and 10 million hatchlings, on La Escobilla beach, in the state of Oaxaca, Mexico, in 1997. A species already under intense threat from human activities can scarcely afford such heavy losses.
Perhaps the most threatened nesting site is located on India's eastern coast at Gahirmatha, in the state of Orissa. Here, numbers dropped from 610,000 nesting females in 1991 to none in 1997. Over the same period, the number of dead olive ridleys found stranded in Orissa increased from 5,250 in 1993 and 1994, to approximately 14,000 in 1997 and 1998. The main cause of this mortality is thought to be in-shore mechanized fishing, in particular shrimp trawling, which is actually illegal in the Marine Sanctuary. In 1999, the authorities caught 51 trawlers and gill-netters illegally fishing in the Sanctuary, and that year the West Bengal Forest Department reported 13,000 olive ridleys killed in Orissa by fishing trawlers. Mangrove forests, which have protected this coast from erosion in the past, are being cleared to make way for a missile testing range and shrimp ponds.
Olive ridleys were once killed in large numbers for meat and leather. There were many economically important slaughterhouses on Mexico’s Pacific coast, and officially over 1 million turtles were killed there each year during the 1960s. This slaughter was reduced when legal quotas were introduced, but an illegal industry still occurs; fortunately, it is not to the extent of earlier years.
WWF's CONSERVATION AND RESEARCH ACTIVITIES
Monitoring trade: Trade Records Analysis of Flora and Fauna in Commerce (TRAFFIC), the wildlife trade monitoring arm of WWF and IUCN, documents the extent of the illegal international trade and is working to bring violations of international treaties to the attention of government authorities. There is still a substantial underground trade in tortoiseshell, turtle leather boots, whole turtles, meat, and eggs. As the trade in sea turtle eggs appears to be on the increase, with several arrests made recently at airports in the USA, TRAFFIC is stepping up its efforts to document its extent so that more effective protection and management can be put in place. TRAFFIC North America has just completed a review and legal analysis of the fisheries and primarily commercial trade in marine turtles in the Bahamas, Cuba, Dominican Republic, Haiti, Jamaica, Mexico, Puerto Rico, Turks and Caicos Islands, British Virgin Islands, and US Virgin Islands.
In 1999, WWF, a network of NGOs, and governments participated in the 2nd Association of Southeast Asian Nations (ASEAN) sea turtle meeting in Sabah, Malaysia. Coordinating regional measures for sea turtle protection is a priority for sea turtle conservationists. Despite government and WWF efforts over the past 30 years, sea turtles are declining throughout the region, affected by coastal development, sand and coral reef mining, pollution, unsustainable egg-collection, and accidental killing by fisheries. In Malaysia alone, the numbers of four species of marine turtles have fallen dramatically in recent decades, with leatherbacks in critical danger. The creation in 1996 of the Turtle Islands Heritage Protected Area, a group of nine islands shared by the Philippines and Sabah, Malaysia, offers some hope for the future.
Western Indian Ocean
In November 1995, WWF co-sponsored an IUCN/SSC Marine Turtle Specialist Group regional meeting to identify priority activities for marine turtle conservation in the western Indian Ocean. WWF is following up on its recommendations and is working to strengthen the network of turtle biologists in the region. WWF has sponsored regional scientists to attend international marine turtle meetings, and co-sponsored a workshop on Turtle Excluder Device (TED) technology for resource managers and fishermen from Kenya, Tanzania, Eritrea, Madagascar, and Mozambique.
In India, WWF filed a petition to the Orissa High Court in 1994 to try to stop development and to protect the environment within the Bhitar Kanika Sanctuary, part of what was once the world’s largest olive ridley rookery on the Gahirmatha coast. In 1998, the court ruled in WWF’s favour and asked the state government to set up a committee for protection, conservation, and research on sea turtles.
Central American Region
WWF is encouraging local communities and fishermen to protect turtles through the use of TEDs. Other initiatives include campaigns to keep trash, such as plastic bags and twine from banana plantations, out of rivers and oceans. On the trade front, WWF is working to halt the sale of turtle products and bring poaching activities to the attention of the authorities. WWF is also encouraging the establishment of wildlife refuges and sanctuaries and supporting patrols on turtle beaches. In addition, WWF is supporting measures to reduce the harmful effects of street lighting near beaches. A major effort to conserve marine turtles in the Central American region is being made through the Central American Environment Programme (Programa Ambiental Centroamericano — PROARCA), which seeks to promote integrated coastal management and protected areas programmes. In October 2000, WWF and its affiliates developed a Marine Turtle Action Plan for Latin America and the Caribbean.
Western Atlantic — the Wider Caribbean
In 1999, WWF co-sponsored a meeting on Marine Turtle Conservation in the Wider Caribbean: a Dialogue for Regional Management. Its recommendations will be used to implement regional cooperation for marine turtle conservation.
Guyana Shield Ecoregion
WWF has been supporting marine turtle conservation in the Guyanas since the 1960s. This biologically rich area comprising Guyana, Suriname, French Guiana, and parts of Venezuela, Colombia, and Brazil has many important turtle nesting beaches. In Suriname, host to the only remaining nesting population of olive ridleys in the western Atlantic, WWF is supporting conservation measures at Galibi Nature Reserve. Through a number of initiatives, WWF is confronting threats from the shrimp industry, over-harvesting, and erosion of nesting beaches. In Brazil, WWF supports Project TAMAR, the national sea turtle programme.
WWF’s associate in Venezuela, FUDENA, has worked for two decades on sea turtle conservation on the Isla de Aves and the Laguna de Tacarigua National Park. The organization's activities on Isla de Aves include yearly monitoring and tagging of females during their nesting period. FUDENA’s ‘Adopt a Sea Turtle’ campaign helps to support this programme. In Laguna de Tacarigua, FUDENA collaborates with several partners to involve local communities in the protection of sea turtle nests.
OTHER CONSERVATION INITIATIVES
Turtle Excluder Devices: After studying turtle mortality in the Gulf of Mexico, the US National Marine Fisheries Service developed TEDs for use by commercial fishermen. TEDs are panels of large mesh webbing or metal grids inserted into the funnel-shaped shrimp nets. As the nets are dragged along the bottom, shrimp and other small animals pass through the TED and into the narrow bag at the end of the funnel. Sea turtles, sharks, and fish too large to get through the panel are deflected out of an escape hatch (the TED), reducing bycatch by up to 97 per cent. There have been problems in implementing TED use, as TEDs allow a small loss of shrimp (about 6%) and many fishermen have refused to use them or sew them up once they are at sea.
Nesting beach conservation projects: Local efforts to conserve olive ridleys are similar to those for other marine turtles. They include: protection of nesting beaches from development; reduction or elimination of egg harvest; public education programmes; relocation of eggs laid in 'unsuitable' locations; lighting bans on the foreshore to prevent hatchlings from being disoriented away from the surf; and legislation to protect adults from hunting. The success of these measures varies considerably from location to location. In Mexico, the decline in the numbers of females nesting at La Escobilla (295,000 nests in 1975; 55,730 in 1988) has been reversed thanks to a complete cessation of hunting of the adults and collection of eggs. Some 700,000 nests were laid between 1994 and 1995. Strict enforcement of protective legislation was crucial to the success of this conservation scheme.
Trade restrictions: Having required its own shrimp fleet to use TEDs, the US State Department then banned shrimp imports from any country (including India and Suriname) that did not take adequate measures to conserve sea turtles in its commercial shrimp fisheries. This was a bold step, and an environmentally important one, because most of the shrimp eaten in the USA is imported, mainly from India and Southeast Asian nations. The ban created international opposition to the use of TEDs, because the USA was perceived as forcing its environmental laws on other nations. In 1997, India, Thailand, Malaysia, and Pakistan successfully challenged the US decision at the World Trade Organization (WTO), despite the existence of exceptions providing for the 'protection of plant, animal and human life…and conservation of natural resources' in the General Agreement on Tariffs and Trade (GATT). Under this provision, the USA could face trade sanctions unless it reversed the ban on imported shrimp caught without TEDs. An appeal, on the grounds that the ban was instigated to protect endangered species, not US trade, is under way.
Egg-collection strategies: Local attempts to conserve olive ridleys by banning egg collection have rarely been successful. Tradition and the economic interests of local communities seem to be too deeply established, and people are often ignorant of the effect of egg collection on adult populations. The most promising schemes try to rationalize egg collection. The number of females involved means that clutches of eggs laid during the first few days of an arribada are frequently disturbed by subsequent nesting and do not develop. In Ostional Wildlife Refuge, Costa Rica, removal of eggs is controlled and restricted to these early eggs so that the overall productivity of the turtles is not compromised. Eggs laid in the dry season are also collected because they rarely develop owing to dehydration. This strategy uses the large volume of ‘doomed’ eggs laid by olive ridleys each year to ensure a constant supply at low prices, and appears to be successful in discouraging other, illegal, collection. Only 6 per cent of eggs available in Costa Rica in 1991 came from beaches other than Ostional.
Ecotourism: Turtles will always be a draw for tourists, who enjoy observing nesting females, hatchlings running to the sea, or adults swimming underwater. The tropical beach holiday industry is dependent in great measure on the welfare of this species (and many others, of course). One of the largest challenges facing marine conservationists is making all the beneficiaries of such holidays (tour operators, local communities, and the tourists themselves) fully aware of this fact.
Since all species of sea turtles are listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the legal international trade involving Party states has largely ceased. However, hunting turtles for international markets outside the CITES framework remains of concern, and local consumption continues. Appendix II species are subject to ‘strict regulation’ and Appendix I ‘must only be authorized in exceptional circumstances’. The olive ridley turtle was added to Appendix II of CITES in 1975 and upgraded to Appendix I of the convention in 1977. There are currently no reservations for the olive ridley and it remains on Appendix I.
As with most other sea turtles, the migratory life of the olive ridley means that successful conservation must be achieved through effective international agreements and conventions. Turtles are ideally matched to the aims expressed by the Convention on the Conservation of Migratory Species of Wild Animals (the Bonn Convention or CMS), which includes many of the concepts fundamental to regional conservation of migratory marine animals and their habitats. All species of sea turtles found in the western hemisphere are listed in both Appendix I and Appendix II of the Bonn Convention.
The Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC) is the major international treaty dedicated exclusively to sea turtles. To date at least ten nations have signed the Convention.
Bjorndal, K. 1995. Biology and Conservation of Sea Turtles. Smithsonian InstitutionPress, Washington, D.C
Kemf, E, Groombridge, B, Abreu, . and A Wilson. 1999. Marine Turtles in the Wild. WWF Species Status Report. WWF International, Gland, Switzerland.
Marine Turtle Newsletter. The newsletter of the Marine Turtle Research Group, University of Wales, Swansea, UK. http://www.seaturtle.org/mtn
TRAFFIC Bulletin. http://www.TRAFFIC.org
WCMC and WWF International. March 2001