|
|
Eretmochelys imbricata
– Critically Endangered
Taxonomy
|
Kingdom:
|
ANIMALIA
|
|
Phylum:
|
CHORDATA
|
|
Class:
|
REPTILIA
|
|
Order:
|
TESTUDINES
|
|
Family:
|
CHELONIIDAE
|
|
Scientific Name:
|
Eretmochelys imbricata
|
|
Species Authority:
|
(Linnaeus, 1766)
|
|
Common Name/s:
|
HAWKSBILL TURTLE (Eng)
CARET (Fre)
TORTUE CARET (Fre)
TORTUE IMBRIQUÉE (Fre)
TORTUE À BEC FAUCON (Fre)
TORTUE À ÉCAILLES (Fre)
TORTUGA CAREY (Spa)
|
Assessment Information
|
Red List Category & Criteria:
|
CR A1bd ver 2.3 (1994)
|
|
Year Assessed:
|
1996
|
|
Annotations:
|
Needs updating
|
|
Assessor/s:
|
Red List Standards & Petitions Subcommittee
|
|
Justification:
|
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:
The two petitions opposing the listing of the Hawksbill Turtle raise similar issues, hence they are considered jointly.
Both petitions challenge the interpretation of the data and the conclusion that there has been an 80% reduction of the global population in the last 3 generations. For species with multiple populations, a listing under A1 needs to weigh the estimated reduction in each population with the relative size of that population 3 generations ago (see Introduction).
The specific disagreements are as follows:
Generation length:
One of the petitions challenges the generation length (35 years) used by the Marine Turtle Specialist Group (MTSG) on the grounds that it ignores areas where the species grows faster (and reaches maturity earlier) and on the grounds that it uses a high estimate for the reproductive lifespan. In general, the S&PS supports the idea of calculating a weighted average of generation length for species that have populations with different generations lengths. [In calculating a weighted average of generation length, it is important to consider the possibility that some of these differences may be due to increased mortality in the recent past due to exploitation by humans. If the generation length varies under threat, the new (2001) IUCN criteria require that the more natural, i.e. pre-disturbance, generation length be used.] In this particular case, even if the generation length were "closer to 25 years" (as the petition states), this would not significantly affect the assessment, because most of the recorded reduction has occurred in the last 20-40 years.
Past reduction:
According to the data presented in the MTSG justification (Meylan and Donnolly 1999; Chelonian Conserv. and Biol. 3:200-224.), there have been large declines in many populations distributed throughout the range. There seems to be no evidence to suggest that the recent declines (last 20-40 years) were preceded by a population increase, so the S&PS regards the declines over the last 20-40 years as a lower bound for the estimated reduction over the last 3 generations.
The petitions mention large and/or stable populations, but this is not inconsistent with long-term reduction. Even if the global population is stable or increasing, there may still be an overall decline of over 80% when a period of three generations is considered. The petitioners present evidence and arguments against current or recent declines (last 5-10 years). However, no data are presented that show increase or stability of a major population in the last 3 generations, whether 75 or 105 years. Thus, although current trends provide important information, they need to be considered in the context of the 3-generation time period for the purposes of Criterion A.
Even if evidence of increase or stability of a major population in the last 3 generations were available, this would not preclude that the global population had declined by 80%. This is because the populations that declined the most (e.g., Indonesia) had made up a much larger proportion of the global population 3 generations ago. The estimates of reduction in different populations should be weighed with the initial abundances (3 generations ago), rather than current abundances. Thus, currently small populations (that have declined a lot) may contribute more to the estimate of global reduction than currently large populations that have remained stable.
Given the uncertainty about the past population sizes, the interpretation of the available information 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 petitions also object to the A1d listing on the grounds that international trade has declined dramatically. However, A1d is based on past, long-term reduction. Therefore, what happened in the last few years is not of direct relevance to the use of A1d. Given the current population sizes and the historical levels of exploitation, a decline of 80% can be inferred.
The S&PS agrees with the petitioners that the MTSG’s justification does not use the data effectively (i.e., it does not weight the trends in different areas). However, the data presented in the justification allows an informed interpretation. As provided in the MTSG’s justification, the information on the various populations is difficult to "unify", as the decline rates are given in a variety of units (catch rates, landings, sightings rates per unit effort, etc). However, based on a rough estimate of the global population size, the size of the pre-1993 catches, and the observed declines in the areas of major population abundance, the S&PS concludes that it is appropriate to infer a reduction of 80% in the last 3 generations.
The petitions also point out that the justification quotes a recommendation to ‘apply the status of the most imperiled population to the entire species.’ This recommendation by Bjorndal (1999; Chelonian Conserv. and Biol. 3:174-76) is definitely a misinterpretation of the criteria, which require that reductions be considered across the entire range of the species. The most appropriate way of doing this is to calculate an average reduction across all populations weighted by their respective population sizes 3 generations ago. However, it does not appear that the assessment actually relies upon this misinterpretation. Although the assessors fail to estimate an overall estimate of reduction, they do present convincing evidence of reductions in excess of 80% over the last 3 generations "at many, if not most of the important breeding sites throughout its global range…" The S&PS concludes that the CR A1 assessment for Hawksbills would stand irrespective of Bjorndal’s recommendation.
On the other hand, it is also inappropriate to base a global assessment only on the best-studied (or, monitored) populations (as one petitioner suggests), especially if these constitute a small fraction of the global population. Although such populations often provide valuable data, restricting a global assessment to these populations might result in a biased estimate, because countries with the least resources for monitoring may also have the least resources for enforcement, the greatest exploitation, and hence the greatest rates of decline. In such cases, it may be unwise to ignore qualitative information about declines from other regions.
Another basis of the petitions’ challenge is the statement in the MTSG’s justification that "the species is not expected to become extinct in the foreseeable future". The S&PS concludes that the petitioner’s criticism on this point is not valid, because the listing is based on quantitative criteria rather than the qualitative beliefs of the Red List Authority.
The petitions also argue that nesting females is not an appropriate index of abundance. For the reasons discussed under the Olive Ridley petition (see Lepidochelys olivacea), the S&PS disagrees with this argument, but also considers "nesting females" only an index of abundance, not direct observation, and has therefore decided to change the listing under A1 to A1bd.
Future reduction:
The petitions also challenge the listing under A2 (future reduction), on the basis of reduced trade, increased conservation efforts, and some increasing or stable populations.
On the one hand, the current trends in trade bans and protected areas suggest a slowing in the rate of population decline. On the other hand, however, increases in the ease of access, availability of technology and size of the human population in developing countries, coupled with the potential transience of international and national trade agreements are also valid factors for consideration in determining the future reduction in the global population of the species. In addition, the depleting stockpile and retained industry infrastructure in Japan, and the dialogue from Cuba are significant points raised by the assessors.
In re-examining all of this relevant information, the S&PS concludes that a future reduction of 80% (in the next 3 generations) does not seem to be well justified. Clearly, it is difficult to make an A2 assessment in the face of such a long generation time, and such unpredictable trends with regard to the threats to the species. The S&PS believes, however, that an estimate of 80% reduction requires more justification, in the form of recent trends in both population numbers and the nature and magnitude of threats. Based on the evidence presented in the justification, the S&PS believes that there is not sufficient basis for a CR A2 listing and removes the listing criterion CR A2bcd. Although the species may qualify for listing under A2 at threat levels lower than CR, this would not change the current listing, because the species qualifies for CR under A1.
|
|
History:
|
| 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) |
| 1996 | - | Critically Endangered (Baillie and Groombridge 1996) |
|
Geographic Range
|
Countries:
|
Native:
American Samoa; Anguilla; Antigua and Barbuda; Aruba; Australia; Bahamas; Bahrain; Bangladesh; Barbados; Belize; Benin; Brazil; British Indian Ocean Territory; Cambodia; China; Colombia; Comoros; Cook Islands; Costa Rica; Cuba; Dominica; Dominican Republic; Ecuador; Egypt; Equatorial Guinea; Eritrea; Fiji; French Guiana; Grenada; Guadeloupe; Guam; Guatemala; Guyana; Haiti; Honduras; India; Indonesia; Iran, Islamic Republic of; Jamaica; Japan; Kenya; Madagascar; Malaysia; Maldives; Marshall Islands; Martinique; Mayotte; Mexico; Micronesia, Federated States of; Montserrat; Mozambique; Myanmar; Netherlands Antilles; Nicaragua; Northern Mariana Islands; Oman; Palau; Panama; Papua New Guinea; Philippines; Puerto Rico; Qatar; Réunion (Mozambique Channel Is.); Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Samoa; Saudi Arabia; Seychelles; Sierra Leone; Solomon Islands; Somalia; Sri Lanka; Sudan; Suriname; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Tokelau; Trinidad and Tobago; Turks and Caicos Islands; United States; Vanuatu; Venezuela; Virgin Islands, British; Virgin Islands, U.S.; Yemen
Regionally extinct:
Cayman Islands
Possibly extinct regionally:
Mauritius
Uncertain presence and origin:
Cameroon; Cape Verde; Côte d'Ivoire; Djibouti; El Salvador; French Polynesia; Gabon; Ghana; Guinea; Guinea-Bissau; Kiribati; Kuwait; Mauritania; New Caledonia; Nigeria; Sao Tomé and Principe; Senegal; Tonga; Tuvalu; United Arab Emirates; United States Minor Outlying Islands; Viet Nam; Western Sahara
|
|
FAO Marine Fishing Areas:
|
Native:
Atlantic-eastern central; Atlantic-northeast; Atlantic-northwest; Atlantic-southeast; Atlantic-southwest; Atlantic-western central; Indian Ocean-eastern; Indian Ocean-western; Mediterranean and Black Sea; Pacific-eastern central; Pacific-northwest; Pacific-southeast; Pacific-southwest; Pacific-western central
|
Habitat and Ecology
|
Habitat and Ecology:
|
Terrestrial nest sites
|
|
System:
|
Terrestrial; Marine
|
|
|
