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Lepidochelys olivacea
– Endangered
Taxonomy
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Kingdom:
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ANIMALIA
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Phylum:
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CHORDATA
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Class:
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REPTILIA
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Order:
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TESTUDINES
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Family:
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CHELONIIDAE
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Scientific Name:
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Lepidochelys olivacea
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Species Authority:
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(Eschscholtz, 1829)
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Common Name/s:
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| English | — | OLIVE RIDLEY, PACIFIC RIDLEY |
| French | — | RIDLEY DU PACIFIQUE, TORTUE BÂTARDE, TORTUE DE RIDLEY, TORTUE OLIVÂTRE |
| Spanish | — | TORTUGA GOLFINA, TORTUGA OLIVACEA |
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Assessment Information
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Red List Category & Criteria:
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EN A1bd ver 2.3 (1994)
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Year Assessed:
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1996
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Annotations:
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Petitioned
Needs updating
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Assessor/s:
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Red List Standards & Petitions Subcommittee
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Justification:
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This revised assessment is a ruling made by the Red List Standards and Petitions Subcommittee (S&PS) after considering all the material provided by the Marine Turtle Red List Authority in support of their 1996 listing and that provided by the petitioner against the listing. The ruling was the conclusion to an appeals process which was initiated following a petition against the 1996 listing of this species (for further details see the IUCN SSC web site).
This ruling is based on the information that was available in 1995, when the listing was made, and on the 1994 Red List Criteria, on which the listing was based. Thus, the S&PS did not consider information that became available after 1995, and the changes to the IUCN criteria that took effect in 2001. The rationale provided by the S&PS for the ruling is as follows:
This petition challenges the listing on the basis of the petitioner’s statement that there is evidence of large numbers of nesting turtles, and increasing numbers in some areas. The justification by the Marine Turtle Specialist Group (MTSG) emphasizes that the listing was based on past reduction, not on current numbers, and states that some of the reported increases occurred after 1995, when the listing was made.
There are two important aspects of the application of criterion A1 to long-lived and widely distributed species such as marine turtles. First, the criterion is based on reduction over the last 3 generations. Thus, recent increases or decreases must be evaluated in the context of long-term change. Second, the criterion is based on the reduction in the global population, not on any specific population. Thus, reductions and increases in different populations must be averaged.
Crude calculations based on the data provided by the MTSG indicate that the reduction since the late 1960s has been close to 50%. The time frame for this decline was about 1 generation. Although the uncertainties in the data prevent an exact calculation of the reduction, it is very likely that the 3-generation reduction has been more than 50%. The petitioner’s figures largely agree with those of the MTSG, except for a few locations. Even considering the numbers used by the petitioner, the S&PS concluded that a 50% reduction is plausible. Given the uncertainty, and the plausibility of a 50% decline, the interpretation of the available information for listing depends on one’s attitude to uncertainty and risk. IUCN guidelines recommend a precautionary attitude and encourage reasoned inference, in order to reduce the chance of Type II errors.
The petition against the Olive Ridley listing also suggested that nesting females is not an appropriate index of abundance (criterion A1b), because high densities in some beaches suggest that the population might have reached its carrying capacity in those areas.
Under the IUCN criteria, "reduction" is defined as a decline in the number of mature individuals. Hence, an "index of abundance appropriate for the taxon" is an observable quantity that correlates reasonably with the number of mature individuals. The general concern in the use of any index of abundance is the validity of the assumptions that are required for the index to accurately reflect the trend in the actual number of mature individuals. Use of "nesting females" to examine population change assumes that the proportion of mature individuals that breed each year, and the number of visits per female per year are reasonably constant (or at least vary randomly) among years. For Olive Ridleys, the MTSG states, "nesting in successive years is commonplace and may be the norm for the species" and "individuals nest 1-3 times/season". If this is true, then the assumption is reasonable. Thus, the S&PS believes that in this case, "nesting females" is an appropriate index of mature individuals, regardless of whether carrying capacity has been reached. The alternative index (suggested by the petitioner) based on feeding ground estimates lacks a clear relationship to "mature individuals" and seems to be more prone to sampling errors.
However, the S&PS disagrees with the MTSG that a count of "nesting females" constitutes direct observation (criterion A1a). The difference between direct observation (a) and index of abundance (b), as well as the value of value of distinguishing between them, lies in the assumptions to be met to provide valid estimates of abundance. While "direct observation" requires only statistical assumptions (e.g., random sampling), indices of abundance require assumptions related to the biology of the species. As discussed above, use of "nesting females" does require such assumptions. Consequently, this measure cannot be considered as direct observation. For this reason, the final decision will list this species as EN A1bd, rather than EN A1abd.
As indicated by the "petitioned" annotation to the listing, this assessment, and in particular the lack of documentation to support the Endangered listing, was petitioned in May 2006. Under the rules of the Petition Process the species had to be reassessed using the 2001 Red List Categories and Criteria before the petition could proceed. A new assessment was prepared by members of the Marine Turtle Specialist Group, however, the petitioner decided not to withdraw the petition as the issues raised previously still applied to the new listing. The final ruling on the outcome of the petition appeared just after the 2007 Red List was released and hence was too late for the new assessment to be included in the 2007 Red List. That assessment will instead be included in the 2008 Red List.
To see the outcome of the ruling by the Standards and Petitions Working Group see: Ruling of the IUCN Red List Standards and Petitions Working Group on Petition against the 1996 listing of Olive Ridley Turtle, 10 September 2007.
To see a copy of the new assessment that will appear in the 2008 Red List see: New Olive Ridley Assessment for the 2008 Red List.
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History:
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| 1982 | - | Endangered (Groombridge 1982) |
| 1986 | - | Endangered (IUCN Conservation Monitoring Centre 1986) |
| 1988 | - | Endangered (IUCN Conservation Monitoring Centre 1988) |
| 1990 | - | Endangered (IUCN 1990) |
| 1994 | - | Endangered (Groombridge 1994) |
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Geographic Range
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Countries:
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Native:
Angola; Australia; Bangladesh; Brazil; China; Colombia; Costa Rica; El Salvador; Eritrea; French Guiana; Guatemala; Guyana; Honduras; India; Indonesia; Kenya; Madagascar; Malaysia; Mexico; Mozambique; Myanmar; Nicaragua; Oman; Pakistan; Panama; Papua New Guinea; Peru; Philippines; Senegal; South Africa; Sri Lanka; Suriname; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Trinidad and Tobago; Venezuela
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FAO Marine Fishing Areas:
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Native:
Atlantic-eastern central; Atlantic-southeast; Atlantic-southwest; Atlantic-western central; Indian Ocean-eastern; Indian Ocean-western; Pacific-eastern central; Pacific-southeast; Pacific-southwest; Pacific-western central
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Habitat and Ecology
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Habitat and Ecology:
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Terrestrial nest sites
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System:
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Terrestrial; Marine
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Bibliography
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Bibliography:
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Baillie, J. and Groombridge, B. (compilers and editors) 1996. 1996 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland. Groombridge, B. (ed.) 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland. Groombridge, B. 1982. The IUCN Amphibia-Reptilia Red Data Book, Part 1: Testudines, Crocodylia, Rhynocehapalia. IUCN, Gland, Switzerland. IUCN Conservation Monitoring Centre. 1986. 1986 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK. IUCN Conservation Monitoring Centre. 1988. 1988 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK. IUCN. 1990. 1990 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK. Marine Turtle Specialist Group. For more information, see the Specialist Group website
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