Important Nesting and Foraging Grounds
The Atlantic Ocean is home to some of the largest nesting rookeries in the world. In Gabon, Africa (south east Atlantic), up to 20,500 female leatherbacks nest per year, making this their largest rookery of all. Other important nesting sites include Trinidad, Panama, Costa Rica, Suriname and French Guinea – just to name a few!
The west Atlantic hosts a variety of nesting sea turtle species. Some of the largest populations of the critically endangered hawksbill turtle, for example, exist in the west Atlantic, from the Caribbean to Mexico and Brazil. Meanwhile, green turtles can be found nesting at more than 700 sites in the west Caribbean. Tortuguero, Costa Rica is famously known for its nesting activity with over 100,000 green turtle nests occurring each year!
As well as important nesting grounds, the Atlantic houses important foraging areas and migratory paths for green turtles. Some green turtle populations frequent the seagrass meadows in Florida, whilst some undergo huge migrations of 1,300 miles between nesting grounds in Ascension Island and foraging grounds off the coast of Brazil.
The northwest Atlantic hosts the largest nesting loggerhead aggregation in the world. Florida makes up for around 90% of this aggregation, with 20,000 loggerhead nests each year (as of the year 2000). However, a recent marked decline to just 8,000 nests in 2020 has raised some concerns over the future of these populations.
The enigmatic and critically endangered Kemp’s ridley turtle is almost exclusively found along the coast of the Gulf of Mexico and the east coast of the USA up to Canada, occupying nearshore habitats with muddy or sandy bottoms. Kemp’s ridleys are very rarely spotted on the east side of the Atlantic on the coast of France or the United Kingdom. Almost 95% of the species’ nesting activity occurs on a single beach in Tamaulipas, Mexico!
Despite being the most ubiquitous and abundant of the world’s seven sea turtle species, olive ridley numbers are relatively low in the Atlantic. A small and declining population of olive ridleys nest on the western coast of Africa.
Have A Question About Sea Turtles?
Sea Turtle FAQ – The Answers to All Your Sea Turtle Questions
Sea turtles can hold their breath for several hours, depending on their level of activity.
If they are sleeping, they can remain underwater for several hours. In cold water during winter, when they are effectively hibernating, they can hold their breath for up to 7 hours. This involves very little movement.
Although turtles can hold their breath for 45 minutes to one hour during routine activity, they normally dive for 4-5 minutes and surfaces to breathe for a few seconds in between dives.
However, a stressed turtle, entangled in a ghost net for instance, quickly uses up oxygen stored within its body and may drown within minutes if it cannot reach the surface.
Learn More About Sea Turtles – Free Online Courses
- Hays GC, Akesson S, Broderick AC, Glen F, Godley BJ, Luschi P, Martin C, Metcalfe JD & Papi F 2001. The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island: dive durations, dive profiles and depth distribution. Journal of Experimental Biology 204: 4093-4098.
- Hays GC, Hochscheid S, Broderick AC, Godley BJ & Metcalfe JD 2000. Diving behaviour of green turtles: dive depth, dive duration and activity levels. Marine Ecology Progress Series 208: 297-298.
- Hochscheid S, Bentivegna F & Hays GC 2005. First records of dive durations for a hibernating sea turtle. Biology Letters 1: 82-86.
- Lutz PL and Musik JA (eds.) 1996. The Biology of Sea Turtles Volume I. CRC Press.
The actual documentation of a sea turtle’s age in the wild is difficult or nearly impossible. Individual turtles can be tracked for a shorter time of six month to three years with the help of satellite transmitters. Longterm studies rely on capture-recapture principle, just like our turtle photo id project. Each photo of a turtle represents a recapture event documenting that the individual is still alive.
A study of nesting green turtles in Hawaii observed female turtles returning to nest for up to 38 years after they were first identified. Assuming the average age at first nesting activity of 24 years, this would show that green turtles can live to up to at least 62 years.
Similar estimates have been made for loggerhead turtles.
- Dodd C 1988. Synopsis of the biological data on the loggerhead sea turtle. Ecology 88.
- Humburg IH and Balazs GH 2014. Forty Years of Research: Recovery Records of Green Turtles Observed or Originally Tagged at French Frigate Shoals in Northwestern Hawaiian Islands, 1973-2013. NOAA Technical Memorandum NMFS-PIFSC-40.
When sea turtles are juveniles, it is very difficult to tell their sex by eye as they do not differ externally. However, after reaching sexual maturity male sea turtles develop a long tail, which houses the reproductive organ. The tail may extend past the hind flippers.
Female turtles have a short tail, which generally doesn’t extend more than 10 cm (4 inches) past the edge of the carapace. Male sea turtles (except leatherbacks) have elongated, curved claws on their front flippers to help them grasp the female when mating.
The sex of a sea turtle embryo is determined by the temperature of the sand: warm temperatures result in more females while cooler temperatures result in more males.
The olive and Kemp’s ridley sea turtles are the smallest species, growing only to about 70 cm (just over 2 feet) in shell length and weighing up to 45 kg (100 lbs). Leatherbacks are the largest sea turtles. On average leatherbacks measure 1.5 – 2m (4-6 ft) long and weigh 300 – 500 kg (660 to 1,100 lbs). The largest leatherback ever recorded was 2,56 m (8.4 ft) long and weighed 916 kg (2,019 lbs) !
55.6-66.0 cm carapace length, weight range of 25-54 kg for nesting females.
- Marquez-M R 1994. Synopsis of Biological Data on the Kemp’s Ridley Turtle, Lepidochelys kempi (Garman, 1880). NOAA Technical Memorandum NMFS-SEFSC-343.
Curved carapace length 52.5-80.0 cm, weight less than 50 kg (average 35.7 kg) for nesting females.
- Qureshi M 2006. Sea turtles in Pakistan. In: Shanker K and Choudhury BC (Eds.). Marine Turtles of the Indian Sub- continent. Heydarabad: India Universities Press, pp. 217–224.Reichart HA 1993.
- Reichart HA 1993. Synopsis of biological data on the olive ridley sea turtle Lepidochelys olivacea (Eschscholtz 1829) in the western Atlantic. NOAA Technical Memorandum NMFS-SEFSC-336.
Nesting females reported between 53.3 and 95.5 cm carapace length, with weight between 27.2 and 86.2 kg.
- Witzell WN 1983. Synopsis of biological data on the hawksbill turtle, Eretmochelys imbricata (Linnaeus, 1766). No. 137. Food & Agriculture Org.
Nesting green females reported curved carapace length 75-134 cm, weight (after egg deposition) 45-250 kg (!).
- Hirth HF 1997. Synopsis of the Biological Data on the Green Turtle Chelonia mydas (Linnaeus, 1758). Vol. 2. Fish and Wildlife Service, US Department of the Interior.
Ones study (Ref. 1) found nesting females have a mean curved carapace length 86.3 cm, and mean weight of 67.4 kg. Another study (Ref. 2) found flatbacks to be between 87.5-96.5 cm.
- Schäuble C, Kennett R and Winderlich S 2006. Flatback Turtle (Natator depressus) nesting at Field Island, Kakadu National Park, Northern Territory, Australia, 1990-2001. Chelonian Conservation and Biology 5: 188-194.
- Limpus CJ 1971. The Flatback Turtle, Chelonia depressa Garman in Southeast Queensland, Australia. Herpetologica 27: 431-446.
Adult loggerhead turtles measure between 65 and 115 cm in curved carapace length and typically weigh between 40 and 180 kg. The largest recorded loggerhead weighed 545 kg and measured 213 cm in presumed total body length. On average, nesting, and therefore adult, female loggerheads have a curved carapace length of 65.1-114.9 cm and weigh between 40.0 and 180.7 kg. Males fall into the same size range (79.0-104.0 cm curved carapace length).
- Brongersma LD 1972. European Atlantic turtles. Zoologische Verhandlingen 121, Leiden.
- Dodd C 1988. Synopsis of the biological data on the loggerhead sea turtle. Ecology 88: 1-119.
- Ernst CH and Lovich JE 2009. Turtles of the United States and Canada, 2nd edition. John Hopkins University Press.
143.8-169.5 cm curved carapace length, weight 259-506 kg recorded for nesting females all around the world. Largest ever recorded specimen was found dead on a beach on the coast of Wales. The adult male turtle weighed 916 kg and its shell was 256.5 cm long. An autopsy revealed that it had drowned.
- Eckert KL and Luginbuhl C 1988. Death of a Giant. Marine Turtle Newsletter 43: 2-3.
- Eckert KL, Wallace BP, Frazier JG, Eckert SA and Pritchard PCH 2012. Synopsis of the Biological Data on the Leatherback Sea Turtle (Dermochelys coriacea). Biological Technical Publication BTP-R4015-2012, US Fish & Wildlife Service.
Each sea turtle species feeds on a specific diet and all lack teeth:
- Flatbacks are mainly carnivorous turtle feeding in shallow waters on soft bottoms.
- Green turtles are vegetarian and prefer sea grasses, sea weeds and algae as adults, however, green turtle hatchlings are omnivorous, eating jellyfish, snails, crabs, and shrimp.
- Hawksbills have a bird-like beak that is used to cut through soft coral, anemones and sea sponges.
- Kemp’s ridleys are omnivores at the beginning of their lives, feeding on seaweed and small creatures like crabs and snails. As adults, Kemp’s ridleys look for food on the seabed, feeding on crustaceans, fish, molluscs, squids and jellyfish.
- Leatherbacks feed mostly on jellyfish.
- Loggerheads feed mainly on hard-shelled organisms such as lobsters, crustaceans, and fish.
- Olive ridleys are omnivorous, mostly eating jellyfish, snails, crabs, and shrimp but they will occasionally eat algae and seaweed as well.
Learn More About Sea Turtles – Free Online Courses
- Briscoe, D.K., Parker, D.M., Bograd, S., Hazen, E., Scales, K., Balazs, G.H., Kurita, M., Saito, T., Okamoto, H., Rice, M. and Polovina, J.J., 2016. Multi-year tracking reveals extensive pelagic phase of juvenile loggerhead sea turtles in the North Pacific. Movement ecology, 4(1), pp.1-12.
- Conant, T.A., Dutton, P.H., Eguchi, T., Epperly, S.P., Fahy, C.C., Godfrey, M.H., MacPherson, S.L., Possardt, E.E., Schroeder, B.A., Seminoff, J.A. and Snover, M.L., 2009. Loggerhead sea turtle (Caretta caretta) 2009 status review under the US Endangered Species Act. Report of the loggerhead biological review Team to the National Marine Fisheries Service, 222, pp.5-2.
- Hays, G.C., Mortimer, J.A., Ierodiaconou, D. and Esteban, N., 2014. Use of long‐distance migration patterns of an endangered species to inform conservation planning for the world’s largest marine protected area. Conservation Biology, 28(6), pp.1636-1644.
- Karl, S.A. and Bowen, B.W., 1999. Evolutionary significant units versus geopolitical taxonomy: molecular systematics of an endangered sea turtle (genus Chelonia). Conservation biology, 13(5), pp.990-999.
- Limpus, C.J., Couper, P.J. and Couper, K.L.D., 1993. Crab Island revisited: reassessment of the world’s largest flatback turtle rookery after twelve years. Memoirs of the Queensland Museum. Brisbane, 33(1), pp.277-289.
- Pritchard, P.C., 1999. Status of the black turtle. Conservation Biology, pp.1000-1003.
- Mast, R.B., Hutchinson, B.J. and Hutchinson, A.H. eds., 2008. Proceedings of the Twenty-fourth Annual Symposium on Sea Turtle Biology and Conservation: 22 to 29 February 2004, San José, Costa Rica (Vol. 567). National Marine Fisheries Service, Southeast Fisheries Science Center.
- Mortimer, J.A. and Carr, A., 1987. Reproduction and migrations of the Ascension Island green turtle (Chelonia mydas). Copeia, pp.103-113.
- National Marine Fisheries Service and US Fish and Wildlife Service (NMFS and USFWS), 2020. Endangered Species Act status review of the leatherback turtle (Dermochelys coriacea).
- US Fish and Wildlife Service, 2007. Hawksbill Sea Turtle (Eretmochelys imbricata). 5-Year Review: Summary and Evaluation.
- US Fish and Wildlife Service, 2014. Olive Ridley Sea Turtle (Lepidochelys Olivacea) 5-Year Review : Summary and Evaluation
- Witt, M.J., Augowet Bonguno, E., Broderick, A.C., Coyne, M.S., Formia, A., Gibudi, A., Mounguengui Mounguengui, G.A., Moussounda, C., NSafou, M., Nougessono, S. and Parnell, R.J., 2011. Tracking leatherback turtles from the world’s largest rookery: assessing threats across the South Atlantic. Proceedings of the Royal Society B: Biological Sciences, 278(1716), pp.2338-2347.