Taxonomy

Dermochelys coriacea | Leatherback

Distribution

Status

Conservation status

HABITATS DIRECTIVE ARTICLE 17 REPORTING*
Range
Unknown
Population
Unknown
Habitat
Unknown
Future Prospects
Unknown
Overall Assessment of Conservation Status
Unknown
Overall trend in Conservation Status
Unknown

* There is currently great uncertainty as to the population ecology, range and habitat usage of Dermochelys coriacea in the east North Atlantic,  hence the use of 'unknown' for all parameters.

Source: NPWS 2013.



IUCN Conservation Status

Ireland (1)
Least Concern
Northwest Atlantic sub-population (2)*Least Concern
Southeast Atlantic sub-population (3)**
Data deficient
Global (4)
Vulnerable [A2bd]

*This population is considered most likely to occur in European waters.

** It is less likely that significant numbers of this population may occur in European populations.

Sources: (1) King, J.L et al 2011; (2) Tiwari, M et al 2013; (3) Tiwari, M et al 2013 (a); (4) Wallace et al 2013;

Legal status

Protected by the following legal instruments:

  • Habitats Directive (92/43/EEC), Annex II, Annex IV
  • Convention on the International Trade in Endangered Species of Flora and Fauna Appendix I
  • Convention of the Conservation of Migratory Species of Wild Animals Appendix I
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix II
  • The Convention for the Protection of the marine Environment of the North-East Atlantic (OSPAR Convention)
  • Wildlife Act (1976), as amended
  • Wildlife (Amendment) Act, 2000

Native status

The 2013 IUCN Global Red List for this species lists Ireland as one of the countries where it is native.

Source: Wallace, B.P.  et al 2013.

Dermochelys coriacea has what has been described as an 'atypical migration pattern'. The species must return to warm tropical waters to breed however females do not breed every year. Instead they spend time between productive temperate waters and warm tropical over-wintering grounds between breeding forays to natal nesting grounds.

It is thought that males may return to breeding grounds more regularly than females.

Source: Doyle, T.K. 2007


Species Biology

Identification

  • The Leatherback Sea Turtle (Dermochelys coriacea) is the largest of the extant sea turtles.
  • Currently individuals are aged based on measurement of Curved Carapace Length (CCL) so that, on average, under 100cms CCL is classed as juvenile, however this age class is rarely seen.
  • Sub-adults have CCL >100cms <120cms and adult (females) 120-140cms with adult males assumed to have the same measurement. Total straight length can be to 2 metres or greater.
  • Average weight for adults females in measured populations (West Atlantic) have been recorded as 327-392 kg, but historic weight for a single captured male is as great as 916kg and there is great variation in recorded female weights between populations (250kgs-500kgs).
  • Front flippers, to total body, are proportionally longer than in other sea turtle species.
  • The Leatherback Sea Turtle does not have the typical keratinous turtle shell but instead has a carapace composed of oily connective tissue covered by a cuticle of bony scales arranged in 7 longitudinal rows, with a ridge between each row.
  • The overall colour of the adult animal is primarily black when seen from above, with intemittent white striping on the carapace ridges and white spotting all over the carapace, head and flippers. The underneath is overall paler. There is much variation in patterning between individuals. All adults have a pink patch on the top of the head, which is associated with the position of the pineal gland.

Source: Eckert K.L. et al, 2012.

  • Due in part to the large size of the adult animal and the layer of oily connective tissue, heat generated by swimming activity is retained in the core of the animal enabling it to maintain a  core temperature higher than the surrounding sea water. This ability allows adults to migrate out of tropical and sub-tropical waters for periods, however a 15°c isotherm in northern, and southern, hemispheres appears to place a limit on how far from the equator the species can migrate.

Source: Doyle, T.K. 2007

Habitat

Habitats include but are not necessarily limited to;

Open marine water (M).

Source: Eckert K.L. et al, 2012; Fossitt, J.A., 2001.

Reproduction

Very little is currently known about the greater part of the life cycle of the Leatherback Sea Turtle (Dermochelys coriacea)- that part spent at sea.

Main nesting sites for Atlantic populations are the northeast coast of South America and the southern Caribbean as well as Gabon on the west coast of Africa. Hatching takes place over a variety of periods  between March and August for the South American / Carribean sites and between November and April for the African sites.

Females excavate a nest and lay 80-100 eggs during the night, before covering the nest and returning to sea. Eggs hatch after between 6 and 13 weeks and hatchlings head to the sea on hatching.

It would appear that smaller, and hence more likely younger, individuals spend most of their time in tropical and sub-tropical waters, but over a certain size, animals can venture into colder, and more northerly, waters in pursuit of what is thought to be the species main food- jellyfish, returning to nesting sites to mate.

Source: Doyle, T.K. (2007)

Females may lay up to 6 clutches of eggs in a nesting season.

Much work needs to be done on the study of the movements and migration of Leatherback turtle hatchlings, juveniles and adult males to give a clearer picture of the overall life cycle of the species.

Source: Eckert K.L. et al, 2012.

Threats faced


THREAT
ARTICLE 17 THREAT CODE
RANKING
Pelagic longlining
F02.01.04
Medium
Threats and pressures from outside the EU territory
XE
Medium
Potting
F02.01.01
Low
Source: NPWS 2013.


The sub-population that visits Irish coastal waters may well be what is termed the Northwest Atlantic sub-population in the IUCN Red List Version 2014.2 i.e. those nesting in the north east coast of South America and in the Carribean. That population is listed as least concern, however the following threats are identified in the IUCN listing for that population (only those threats that may be appropriate within Irish waters are listed);

  • Fishing & Harvesting Aquatic Resources : Unintentional Effects [this most likely refers to by-catch of the species during commercial fishery practices and entanglement in fixed fishing gear.].
  • Pollution and Pathogens: marine pollution and debris that affect marine turtles (i.e. through ingestion or entanglement, disorientation caused by artificial lights), as well as impacts of pervasive pathogens (e.g. fibropapilloma virus) on turtle health.
  • Climate change.


Source: Tiwari, M et al, 2013.


The sub-population termed the Southeast Atlantic sub-population in the IUCN Red List Version 2014.2 i.e. those nesting in Gabon on the west coast of Africa appear to use the south Atlantic for foraging however there is currently insufficent data to exclude the possibility of individuals from that population visiting Irish waters. Threats faced by individuals from that population when in Irish waters would be as for the Northeast Atlantic population.

Source: Tiwari, M et al 2013.

The Irish Red List of Reptiles, Amphibians and Freswater Fish (King et al 2011) lists the following threats that may be applicable within Irish waters;

  • By catch, particularly in longline fisheries
  • Accidental consumption of marine pollution (e.g. plastic bags)
Source: King et al, 2011.

In 'Leatherbacks in Irish Waters' Irish Wildlife Manual No. 32. Doyle, T.K. (2007)  the primary threats to individuals of the species in Irish waters are suggested as being from;

  •     Fixed Fisheries;
        Animals become entangled in gear, particularly ropes associated with, for example lobster and crab pots.

  •     Salmon Drift nets;
        These are now largely illegal in Ireland, but may be used illegally and drift nets are used for other species.

  •     Marine Pollution;
        In particular plastic bags which, it is thought, can be mistaken as prey by the turtle. When swallowed the digestive system             disrupted.


Source: Doyle, T.K., 2007.


Conservation actions

In the Article 17 Habitats Directive reporting for the period 2007-2012 no Conservation Measures  in place or in the process of being implemented during the period were listed for this species, however it is acknowledged that this is due primarily to the fact that there is currently insufficient information available on the ecology, distribution and numbers of the species in Irish waters to make an assessment in line with the requirements of the Habitats Directive reporting categories.

The IUCN Red List suggested Conservation Actions for the Northwest Atlantic population of this species in Version 2014.2 include;

  • Site / area protection
  • Site / area management
  • Awareness and communication
  • Legislation (this is at international, national and sub-national level)
Suggested Conservation Actions for the Southeast Atlantic population are the same. For both populations 'Harvest Management' is included and could be interpreted as managing the collection of the eggs of the species by humans for food or other uses, which would not be an action applicable to Ireland. 

Distribution

World distribution(GBIF)

East and west coasts of America and throughout area of the North Atlantic. Populations have also been recorded in coastal areas of Australia (especially south coast). Generally fewer records from southern hemisphere.

Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.

Irish distribution





Temporal change

Records submitted to Data Centre in 2021

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

The National Biodiversity Data Centre is trying to improve our knowledge on the distribution of the Leatherback Sea Turtle in Irish waters. Should you observe the species, please submit sightings to add to the database. Detailed observations will assist us gaining a better insight into where the species is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:

http://records.biodiversityireland.ie/submit_records.php?fk=SeaTurtleStandard

All records submitted on line can be viewed on Google Maps – once checked and validated these will be added to the database and made available for conservation and research.

Further information

For further information contact Dr. Tom Doyle tom.doyle@nuigalway.ie

References

Publications

Doyle, T.K. (2007) Leatherback Sea Turtles (Dermochelys coriacea) in Irish waters.Irish Wildlife Manuals, No.32. National Parks and Wildlife Service, Departmentof the Environment, Heritage andLocal Government, Dublin, Ireland.

Eckert K.L., Wallace B.P., Frazier J.G. ,  Eckert S.A., Pritchard P.C.H, (2012), Synopsis of the Biological Data on the Leatherback Sea Turtle(Dermochelys coriacea), Biological Technical Publication, BTP-R4015-2012, U.S. Fish & Wildlife Service. 

Fossitt, J.A., (2001). A Guide to Habitats in Ireland. The Heritage Council.

King, J.L., Marnell, F., Kingston, N., Rosell, R., Boylan, P., Caffrey, J.M., FitzPatrick, Ú., Gargan,P.G., Kelly, F.L., O’Grady, M.F., Poole, R., Roche, W.K. & Cassidy, D. (2011) Ireland Red List No. 5:Amphibians, Reptiles & Freshwater Fish. Nation

NPWS (2013) The Status of EU Protected Habitats and Species in Ireland.  Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

Tiwari, M., Wallace, B.P. & Girondot, M. 2013. Dermochelys coriacea (Northwest Atlantic Ocean subpopulation). The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 01 October 2014.

Tiwari, M., Wallace, B.P. & Girondot, M. 2013(a). Dermochelys coriacea (Southeast Atlantic Ocean subpopulation). The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 01 October 2014.

Wallace, B.P., Tiwari, M. & Girondot, M. 2013. Dermochelys coriacea. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 30 September 2014.

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