Sea Turtle Species
Loggerhead Sea Turtle (Caretta caretta)
Description
Loggerheads are large, hard-shelled sea turtles. They have huge heads and powerful jaws for feeding on shelled prey such as whelks and conchs. This sea turtle species is called a “loggerhead” because when resting at sea with just their heads out of the water, sailors often mistake them for floating logs.
They have a slightly heart-shaped carapace, which is often covered with commensal organisms such as barnacles and algae. It is estimated that up to 100 species may live on the carapaces of loggerhead turtles. This makes each turtle its own mobile ecosystem.
The carapace of adults is reddish-brown. The carapace of hatchlings is brown to dark gray. They also have a distinctive species-specific pattern to their scutes.
The skin of males is more brown and the head more yellow than those of females. Males also have wider carapaces and a long curved claw on each forelimb. Both males and females have two claws on each flipper.
Distribution
The loggerhead sea turtle is found in more places around the world than any other species of sea turtle. They are found throughout both temperate and tropical waters. They are found along the continental shelves and river estuaries of the Atlantic, Pacific and Indian Oceans. They are also found in the Mediterranean Sea. The largest nesting area is along the southeast coast of the United States, from North Carolina to Florida.
Adult loggerheads are known to make long migrations between feeding areas and nesting beaches. When not nesting, adult females born on U.S. beaches are distributed in waters off the eastern U.S. and throughout the Gulf of Mexico, Bahamas, Greater Antilles and Yucatán.
Habitat
Loggerheads occupy three different ecosystems during their lives:
- Sandy beaches
- Open ocean
- Nearshore coastal areas
Loggerheads nest on ocean beaches, generally preferring high energy, relatively narrow, steeply sloped and coarse-grained beaches.
Diet
Loggerhead turtles are omnivores, eating both plants and animals. They mostly eat animals. They use their massive and powerful jaws to break open the hard shells of such prey as whelks and conchs. They also eat many other invertebrates such as jellyfish, shrimp, sea urchins, octopus and squid.
Life History
Loggerheads spend most of their lives in the open ocean or in shallow coastal waters. They almost never come ashore. Adult females only come ashore to nest. Males usually don’t come ashore at all. Adults tend to return to the same nesting grounds year after year and many females return to the very beach where they themselves hatched.
BreedingAs breeding season approaches, turtles migrate from their feeding areas to mating areas that are located just offshore of the nesting beaches. Loggerheads have some of the longest migration routes of any sea turtle. Pacific loggerheads migrate over 7,500 miles (12,000 km) between nesting beaches in Japan and feeding grounds off the coast of Mexico.
The males arrive first. Courtship and mating begin once the females arrive. Mating occurs from mid-March through early June each year. In Georgia, South Carolina and North Carolina nesting begins in May and ends in August. Most adult males return to the feeding grounds in mid-June. The females remain until they finish nesting on the nearby beaches.
NestingFemale loggerheads nest only every two to three years. They usually crawl onto the beaches and nest at night. The turtles dig an egg chamber with their back flippers, deposit eggs, cover the nest with sand and return to the ocean. This process takes about one to two hours.
Each female usually lays between one and seven clutches of eggs during a nesting season. There are approximately 14 days between clutches. Between clutches, they return to the sea and mate. The clutch size averages between 100-125 eggs. After the female has produced her last nest, she too leaves and begins the long journey back to her feeding grounds.
Sometimes you don’t actually have to see the turtle to know which species has been on a beach. When nesting females come onto a beach, they leave tracks, or “crawls”, made by their front flippers. These “crawls” are distinctive for each species.
Incubation and HatchingThe eggs incubate from 53 to 80 days and (if left alone) up to 75% of the eggs laid successfully hatch. Environmental temperature is very important to developing eggs. How fast the egg develops (length of incubation) depends on the temperature within the nest. This temperature can be affected by sun, shade, rain, heat generated within the nest and an egg’s position in the nest. At cool temperatures, around 25ºC (77ºF), incubation can last 65 to 80 days. At warmer temperatures, around 35ºC (95ºF), incubation lasts for 45 to 60 days. Eggs incubated at too cold or too hot a temperature will not hatch.
The sex of the turtle is also determined by the temperature of the nest during the middle third of incubation (this is called temperature dependent sex determination, or TSD).
Loggerheads usually hatch at night. Immediately after hatching, the hatchlings dig through the sand surrounding the nest towards the surface. Once on the surface, the hatchlings quickly orient and move towards the ocean using moonlight on the water as a guide. Once in the water, the hatchlings swim for about 20 hours. This takes them about 14-17 mi (22-28 km) offshore. At this point, they hide in sargassum rafts or debris. Upon reaching about 18 in (45 cm) in length, they migrate to near shore and river estuaries of the eastern United States, the Gulf of Mexico and the Bahamas.
Bowen, B.W.; Abreu-Grobois, F.A.; Balazs, G.H.; Kamezaki, N; Limpus, C.J.; Ferl, R.J. (1995). Trans-Pacific migrations of the loggerhead turtle (Caretta caretta) demonstrated with mitochondrial DNA markers”(PDF). Proc. Natl. Acad. Sci. USA 92 (9): 3731–4. doi:10.1073/pnas.92.9.3731. PMC 42035. PMID 7731974.
Conant, Therese A.; Peter H. Dutton, Tomoharu Eguchi, Sheryan P. Epperly, Christina C. Fahy, Matthew H. Godfrey, Sandra L. MacPherson, Earl E. Possardt, Barbara A. Schroeder, Jeffrey A. Seminoff, Melissa L. Snover, Carrie M. Upite, and Blair E. Witherington (2009). Loggerhead Sea Turtle (Caretta caretta) 2009 Status Review Under the U.S. Endangered Species Act (PDF). Loggerhead Biological Review Team.
Dodd, Kenneth (1988). “Synopsis of the Biological Data on the Loggerhead Sea Turtle Caretta caretta (Linnaeus 1758)” (PDF). Biological Report 88 (14) (FAO Synopsis NMFS-149, United States Fish and Wildlife Service): 1–83.
Ernst, C. H.; Lovich, J.E. (2009). Turtles of the United States and Canada (2 ed.). JHU Press. ISBN 978-0-8018-9121-2.
Janzen, Fredric J (1994). “Climate change and temperature-dependent sex determination in reptiles” (PDF). Population Biology 91 (16): 7487–7490.
Lorne, Jacquelyn; Michael Salmon (2007). “Effects of exposure to artificial lighting on orientation of hatchling sea turtles on the beach and in the ocean” (PDF). Endangered Species Research 3: 23. doi:10.3354/esr003023.
Miller, Jeffrey D.; Limpus, Collin J.; Godfrey, Matthew H. (2003). “Nest site selection, oviposition, eggs, development, hatching and emergence of loggerhead turtles”. In Bolten, A., Witherington, B. Loggerhead Turtles. Smithsonian Books. pp. 125–143. ISBN 1588341364.
National Marine Fisheries Service and U.S. Fish and Wildlife Service (1998). Recovery Plan for U.S. Pacific Populations of the Loggerhead Turtle (Caretta caretta) (PDF). Silver Spring, MD.: National Marine Fisheries Service. Archived from the original on 2010-10-25. Retrieved 2010-10-25.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
US Fish and WIldlife Service, North Florida Ecological Services, Loggerhead Turtle Fact Sheet.
Witherington, Blair (2006). “Ancient Origins”. Sea Turtles – An Extraordinary Natural History of Some Uncommon Turtles. St Paul, Minnesota: MBI Publishing Company. ISBN 0-7603-2644-4.
Yntema, C.; N. Mrosovsky (1982). “Critical periods and pivotal temperatures for sexual differentiation in loggerhead sea turtles”. Canadian Journal of Zoology 60 (5): 1012–1016. doi:10.1139/z82-141. ISSN 1480-3283.
Description
The green sea turtle is the largest of the hard-shelled sea turtles. The carapace is smooth and heart-shaped. The color of the carapace varies and has shades of black, gray, green, brown, and yellow. The plastron is yellowish white. The head appears small when compared to the body.
Greens have a single claw on each flipper. They have a distinctive pattern of scales and scutes as well. Their body fat is green.
Hatchlings have a black carapace, white plastron and white edging on the shell and limbs.
Distribution
Green sea turtles are found in tropical and subtropical waters throughout the world. They live in the coastal areas of more than 140 countries and nest on the beaches of over 80 countries.
In the United States, green sea turtles are found in near-shore waters along the gulf coast and Atlantic coasts as far north as Massachusetts. They are also found in the U.S. Virgin Islands and Puerto Rico. There are many important feeding areas in Florida. Along the Pacific coast, green sea turtles have been sighted from Baja California to southern Alaska. In the central Pacific, green turtles occur around most tropical islands, including the Hawaiian Islands.
Green sea turtles will migrate long distances between feeding grounds and nesting beaches.
Habitat
Green sea turtles use three different habitats depending on their age:
- Sandy beaches
- Open ocean
- Reefs, bays, protected inlets
Greens mature, feed and nest in very different areas. As hatchlings and youngsters, they are found in open oceans associated with sargassum rafts. When they reach 20 to 25 cm (8 to 10 inches) in length, they leave these rafts and move to feeding grounds. These feeding grounds are found in the relatively shallower waters of reefs, bays and protected inlets. They prefer open beaches with a sloping approach for nesting. As they move between feeding grounds and nesting beaches, they spend time in the open ocean.
Diet
When young, green sea turtles eat a variety of plants and small animals (omnivorous) found in and around the sargassum rafts. As adults, they eat mainly sea grass and algae (herbivorous). It is believed that the green color of their fat is a result of this diet.
Life History
Green sea turtles, like all sea turtles, spend most of their lives in the water. In general, once sea turtles enter the water, they never come back on land except to nest. However, the green sea turtle occasionally comes ashore to bask.
BreedingWith many reptiles, size is a more reliable indicator of sexual maturity than age. This is the case with sea turtles. It is estimated that male and female green sea turtles become large enough to be sexually mature between 20 and 50 years of age. When ready to breed, males and females migrate from their foraging areas to waters just off shore from the nesting beaches. Mating occurs in these waters. The breeding season is from June to September.
NestingFemales are known to nest on the same beaches on which they were born. They often travel thousands of miles between feeding and nesting areas.
Individual females usually nest only once every two to four years. When a female is ready to lay eggs, she crawls onto the beach – usually at night. She crawls until she is above the high tide line. She then digs a deep nest with her rear flippers. She deposits up to 200 eggs into the nest. When finished laying eggs, she covers the clutch with sand, disturbs the general area and returns to the ocean. She leaves behind a distinctive crawl pattern. The egg laying process takes an average of two hours.
She may repeat this process every 12 to 14 days until she has laid as many as seven separate clutches (usually three to four). When she is finished laying all of her eggs she returns to the sea to begin the long journey back to her feeding grounds.
Incubation and HatchingIncubation lasts from 45 to 75 days. Like most reptiles, the temperature at which an egg is incubated determines its sex. This is referred to as temperature dependent sex determination, or TSD. Hatching rates of undisturbed nests are usually high.
Hatchlings usually emerge from the nest at night. After the little hatchlings dig their way out of the nest, they quickly orient and move towards the ocean. They use moonlight and starlight reflected from the surface of the water as a guide. Once in the ocean, they swim for a long time without stopping. It is thought that they find beds or rafts of sargassum algae to float around with. It is there that they begin to eat and grow.
Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington and London: Smithsonian Institution Press.
Sea Turtle Conservancy. Species Fact Sheet: Green Sea Turtle (Online). Accessed March 30, 2012.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
US Fish and WIldlife Service, North Florida Ecological Services, General Sea Turtle Information.
Description
The leatherback sea turtle is the largest sea turtle. The largest turtle on record measured almost 7 feet (2.1 m) in length. The leatherback does not have a solid, external bony shell like all of the other sea turtles. Rather, it has a loose bony structure covered by dark brown or black rubbery skin. This shell is about an inch and a half thick. The carapace has seven pronounced ridges that run from front to back. The lighter colored plastron has five ridges. Neither the front or back flippers have claws or scales. The flippers are longer relative to their body than those of other sea turtles. Hatchlings are heart-shaped and have white striping along the ridges of their backs and on the margins of the flippers.
This species has unique adaptations – even for sea turtles. Several adaptations make it possible for them to live in colder water than other sea turtle species. They have a network of blood vessels that work as a heat exchanger and a thick insulating layer of oils and fats in their skin. This, and their large size, makes it possible to maintain body temperatures that are much higher than the surrounding environment (Spotila, 2004). Other adaptations help leatherback turtles eat soft, gelatinous food like jellyfish. Pointed cusps and sharp-edged jaws act like teeth while backwards pointed papillae cover the throat, keeping the food headed towards the stomach and protecting the turtle from jellyfish stings.
Distribution
The leatherback is the most wide-ranging of the sea turtles. They have a nearly worldwide distribution and travel long distances from their nesting beaches to their feeding grounds. They are mainly found in warm tropical waters. However, larger adults (those more than three feet in length) can also be found in colder water. These bigger turtles can be found far north as the cold subartic waters of Newfoundland, Nova Scotia and Labrador. They can also be found in the cold waters of southern Argentina and South Africa. Smaller animals are almost always found in warmer tropical waters.
Leatherback turtle nesting grounds are also located around the world, mostly on tropical beaches. The largest remaining nesting areas are found on the coasts of northern South America and West Africa. Within the U.S., there are small nesting colonies in the Caribbean and in southeast Florida.
Habitat
Leatherbacks use three different ecosystems during their lives:
- Sandy beaches
- Open ocean
- Coastal waters
They spend most of their time in open ocean throughout the world. They are deep divers and have been found at depths of over 4000 ft (1219 m). They can also be seen feeding in coastal waters. Breeding females nest on narrow tropical sandy beaches backed with vegetation.
Diet
Leatherbacks are primarily carnivorous. They eat soft-bodied prey found in the open ocean such as jellyfish and other invertebrates without shells. They will occasionally eat algae and seaweed.
Life History
Leatherbacks spend most of their lives in the open ocean. Little is known about the life history of hatchling to juvenile leatherbacks. Adult females only come ashore to nest. Males usually don’t come ashore at all. The life span of the leatherback is unknown but believed to be approximately 50 years in the wild.
BreedingLeatherbacks are thought to reach sexual maturity in about 16 years. However, as with many reptiles, size is a more reliable indicator of sexual maturity than age. Leatherbacks migrate to areas just offshore of common nesting beaches. They mate in these areas and as they travel to them. Males tend to return to locations where they have mated successfully in previous seasons.
NestingLeatherback females don’t always return to the same beaches, but do nest in the same general area. Females only nest once every two to three years and only during a specific time of year. Along the North American east coast, nesting occurs from March to July. When a female is ready to lay her eggs, she swims up to the nesting beaches at night. She then crawls up the beach until she is above the high tide line and digs an egg chamber with her back flippers. She deposits about 100 eggs into the egg chamber. About 30% of these eggs will be infertile. She then covers the nest with sand, disturbs a large area around the nest and returns to the ocean. Like other sea turtles, she leaves behind a distinctive, species-specific crawl pattern.
The female will repeat this pattern (renest) an average of four to seven times over the season, returning to the beach every 12 days. When a female is finished nesting, she will migrate from tropical to cooler waters. These cooler waters support high densities of her primary food – the jellyfish.
Incubation and HatchingThe eggs incubate from 60 to 75 days. Environmental temperature is very important to developing eggs. The speed of development within the egg (length of incubation) depends on the temperature in the nest. This temperature can be affected by sun, shade, rain, heat generated within the nest, and an egg’s position in the nest. Warmer nests hatch more quickly.
Like most reptiles, the sex of the turtle is also determined by the temperature of the nest during the middle third of incubation. This is called temperature dependent sex determination, or TSD.
Leatherback hatchlings usually emerge from the nest at night. Once on the surface they quickly orient and move towards the ocean. They use moonlight reflected from the surface of the water as a guide.
Beacham, W., F. Castronova, S. Sessine. 2000. Beacham’s Guide to the Endangered Species of North Ameica, volume 1: Mammals, Birds, Reptiles. Detroit: Gale Virtual Reference Library. Accessed July 15, 2014 at http:// www. gale. com/eBooks.
Carr, A. 1952. Handbook of Turtles. Ithaca, NY: Comstock Publishing Associates.
Sea Turtle Conservancy. Species Fact Sheet: Leatherback Sea Turtle (Online). Accessed March 30, 2012.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
Description
The hawksbill is small to medium-sized sea turtle species. The carapace is dark to golden brown, with streaks of orange, red and/or black. The plastron is yellow. The hatchlings are mostly brown.
Hawksbill turtles have several features that distinguish them from other species of sea turtle. They have two pairs of prefrontal scales on the top of the head. Each of the flippers has two claws. Some of the scutes on the carapace overlap each other. The side and back edges of the carapace are serrated. Most notably, the elongated mouth resembles a bird’s beak.
Young hawksbills have a heart-shaped carapace. As they age the carapace becomes elongated.
Distribution
Hawksbills can be found throughout the tropical waters of the Pacific, Atlantic and Indian oceans. They regularly occur in southern Florida and the Gulf of Mexico (especially Texas), in the Antilles and along Central America as far south as Brazil.
Like several other sea turtle species, the hawksbill is capable of migrating long distances between nesting beaches and foraging areas. For example, one female hawksbill traveled 1,160 miles from US Virgin islands to Nicaragua.
The most important nesting areas in the U.S. are in Puerto Rico and the U.S. Virgin Islands. Within the continental U.S., nesting occurs along the southeast coast of Florida and the Florida Keys. A few hawksbills have been reported nesting along the coasts of North Carolina and South Carolina.
Habitat
Hawksbill turtles use different habitats at different stages of their life.
- Open ocean
- Coastal areas (coral reefs, estuaries, bays)
Hatchlings and juveniles are found in the open ocean. They occupy floating mats of algae and drift lines of flotsam and jetsam in the Atlantic. The habitat of hawksbill hatchlings and juveniles in the Pacific is unknown.
When they are 8-10 inches long, these juveniles move to coastal areas where they can forage. These areas are hard-bottomed reef habitats containing sponges. It is here that they begin to feed below the surface on animals living in the coral reefs. They are usually found in water no deeper than sixty feet.
Hawksbills are also found around rocky outcrops and high energy shoals. They are also known to inhabit mangrove-fringed bays and estuaries, where coral reefs are absent.
Diet
As adults, hawksbills eat mostly sponges but will sometimes eat invertebrates and algae as well.
Life History
Once males leave their nesting beach they spend the rest of their lives in the water. Females only come ashore to nest. The lifespan of these animals is unknown but thought to be around 30 years.
BreedingWith many reptiles, size is a more reliable indicator of sexual maturity than age. This is the case with sea turtles. Male hawksbills mature when they are about 27 inches (70 cm) long. Females mature at about 30 inches (80 cm). The specific ages at which wild turtles usually reach these lengths are unknown, but it is thought to be between three and four years of age. Sexually mature hawksbills migrate between feeding and nesting areas. Mating usually begins in shallow waters off-shore from the nesting beaches.
NestingFemales return to the beaches where they were born (their natal beaches) to nest. Females only nest once every two to three years and only during a specific time of year. Nesting usually occurs between April and November. A female hawksbill generally lays 3-5 nests at 14-16 day intervals each season. The nests each contain an average of 130 eggs.
Female hawksbills usually nest at night high up on the beach under or in the beach/dune vegetation. They commonly nest on pocket beaches, with little or no sand. The nesting process can last as little as 45 minutes or as long as 3 hours. The females clear an area, dig an egg chamber, lay their eggs, fill in the chamber, disturb the area and crawl back to the sea. They leave behind a distinctive crawl pattern.
Incubation and HatchingThe eggs incubate for 60 to 75 days. It is thought that, like other sea turtles, sex determination is temperature dependent, known as TSD. However, there is not enough data to confirm this in this species.
Hatchlings usually emerge from the nest at night. Once on the surface, they quickly orient and move towards the ocean. They use moonlight and starlight reflected from the surface of the water as a guide.
Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington and London: Smithsonian Institution Press.
Sea Turtle Conservancy. Species Fact Sheet: Hawksbill Sea Turtle (Online). Accessed March 30, 2012.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
US Fish and WIldlife Service, North Florida Ecological Services, Loggerhead Turtle Fact Sheet.
Description
Adult Kemp’s ridleys are the smallest of the sea turtles, with the carapace rarely exceeding 29 inches in length. The carapace of an adult Kemp’s Ridley is broad and light gray-olive in color and the plastron is creamy white. The carapace is usually as wide as it is long and has a distinctive pattern of scutes. The head is large with ridged, powerful jaws. Each of the front flippers has one claw, while the back flippers may have one or two. Hatchlings are grey-black all over.
Distribution
Kemp’s ridleys can be found throughout the Gulf of Mexico and the U.S. eastern coast from New England to Florida. Almost all the Kemp’s ridleys in the world nest on one beach at Rancho Nuevo, Tamaulipas, Mexico. Nesting has also been reported throughout the Gulf of Mexico, as well as along the eastern coasts of Florida, Georgia, South Carolina and North Carolina.
Habitat
Kemp’s ridleys occupy different habitats depending on their age. They mature, feed and nest in very different areas.
As hatchlings and youngsters, they spend the first few years in the open ocean. Here they associate with floating mats of sargassum seaweed. When the turtles reach a carapace length of about 8 inches (20 cm), they travel to the shallow bays and lagoons of the Gulf of Mexico or northwestern Atlantic Ocean to feed and develop until they reach adulthood.
Adult Kemp’s ridleys mainly stay near shallow coastal regions (less than 160 ft deep) and can be found in bays and lagoons. These turtles prefer waters that have sandy or muddy bottoms. They can also be found in the open ocean, especially when traveling between feeding and nesting areas. At sea, this species have been known to dive to great depths.
Diet
Their diet consists mainly of swimming crabs, but may also include fish, jellyfish and an array of mollusks.
Life History
Once turtles have entered the sea, they seldom return to land. Males never come ashore. Females only come on shore to nest. With many reptiles, size is a more reliable indicator of sexual maturity than age. This is the case with sea turtles. Kemp’s ridleys take from 11 to 35 years to reach maturity. Females usually start nesting when they are between 10 and 17 years of age.
BreedingIndividual male Kemp’s ridleys may have different breeding strategies. Some males migrate annually between feeding and breeding grounds. Others do not appear to migrate at all. They stay in one area and breed with females they encounter by chance.
Female Kemp’s ridleys migrate to and from nesting beaches approximately every two years. Breeding season occurs from March to August.
NestingNesting peaks between in May and June. Unlike most other sea turtles, nesting occurs during the day. Kemp’s ridley turtle exhibit mass synchronized nesting known as ‘arribadas‘ (Spanish for ‘mass arrivals’). During arribadas, thousands of females come ashore to nest on the same beach at the same time. No one knows for sure what triggers an arribada.
Nesting females crawl onto the beaches above the high tide line and dig a nest cavity with their rear flippers. They deposit their eggs into the nest, cover the nest with sand and return to the sea. The entire process takes about an hour. Females repeat this process two or three times during the breeding seasons at approximately 14 day intervals. Each clutch contains about 100 eggs. After females have completed nesting, they return to their foraging areas.
Incubation and HatchingEggs incubate for 48-56 days. Like most reptiles, the temperature at which an egg is incubated determines its sex. This is referred to as temperature dependent sex determination, or TSD.
It may take several days for a hatchling to emerge from the nest. They usually emerge at night. Once on the surface, they quickly orient and move towards the ocean. They use moonlight and starlight reflected from the surface of the water as a guide.
After entering the water, the hatchling swims continuously for 24 to 48 hours. It is thought that they find beds/rafts of sargassum algae to float around with. It is there that they begin to eat and grow.
Ernst, C. H.; Lovich, J.E. (2009). Turtles of the United States and Canada (2 ed.). JHU Press. ISBN 978-0-8018-9121-2.
Janzen, Fredric J (1994). “Climate change and temperature-dependent sex determination in reptiles” (PDF). Population Biology 91 (16): 7487–7490.
Lorne, Jacquelyn; Michael Salmon (2007). “Effects of exposure to artificial lighting on orientation of hatchling sea turtles on the beach and in the ocean” (PDF). Endangered Species Research 3: 23. doi:10.3354/esr003023.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
US Fish and WIldlife Service, North Florida Ecological Services, Kemp’s Ridley Turtle Fact Sheet.
Witherington, Blair (2006). “Ancient Origins”. Sea Turtles – An Extraordinary Natural History of Some Uncommon Turtles. St Paul, Minnesota: MBI Publishing Company. ISBN 0-7603-2644-4.
Wynne, Kate; Schwartz, Malia (1999). Guide to Marine Mammals and Turtles of the U.S. Atlantic and Gulf of Mexico. illustrated by Garth Mix (2nd ed.). Rhode Island Sea Grant. ISBN 0-938412-43-4.
Description
The adult olive ridley is relatively small. It can weigh up to 100 lbs and be as long as 30 inches. Its carapace is olive colored and heart shaped. This species varies somewhat in color, size and shape from region to region. The largest animals occur on the Pacific coast of Mexico. Each flipper has one or two claws.
Distribution
Olive ridleys can be found in the tropical regions of the south Atlantic, Pacific and Indian Oceans. In the south Atlantic they can be found along the coasts of west Africa and South America. In the eastern Pacific they occur from southern California to northern Chile. Adult olive ridleys often migrate long distances between feeding and breeding grounds. Although nesting occurs in 40 different countries, arribadas occur only on a few beaches in the eastern Pacific and northern Indian oceans.
Habitat
Olive ridleys occupy different habitats depending on their age. They mature, feed and nest in very different areas.
They spend the first few years in the open ocean. Here they associate with floating mats of sargassum seaweed. As juveniles they move within 10 mi (15 km) of shore using the shallower waters for feeding. Adult females use sandy beaches for nesting.
Diet
The Olive ridley eats a wide variety of food items. They eat algae, lobster, crabs, mollusks, shrimp, soft fleshy marine invertebrates and fish. They often dive to depths of 500 feet to forage on invertebrates.
Life History
With many reptiles, size is a more reliable indicator of sexual maturity than age. This is the case with sea turtles. Olive ridleys reach sexual maturity at about 15 years of age. When ready to breed, both males and females travel from feeding grounds to breeding areas just off shore of nesting beaching. Females return to the beach on which they were born to nest.
NestingThe olive ridley, like the Kemp’s ridley, has one of the most unusual nesting habits in the natural world. They exhibit mass synchronized nesting known as ‘arribadas‘ (Spanish for ‘mass arrivals’). Large groups of turtles gather off shore of nesting beaches. Then, all at once (usually at night), large numbers of female turtles come ashore and nest. Females dig nests with their rear flippers that are 12-22 in (30-55 cm) deep. They deposit their eggs into the nest, cover the nest with sand and return to the sea. Female olive ridleys nest every year. They produce one or two clutches of 100 eggs each season.
Incubation and HatchingIncubation takes approximately 60 days. Like most reptiles, the temperature at which an egg is incubated determines its sex. This is referred to as temperature dependent sex determination, or TSD.
It may take several days for a hatchling to emerge from the nest. They usually emerge at night. Once on the surface, they quickly orient and move towards the ocean. They use moonlight and starlight reflected from the surface of the water as a guide. After entering the water, the hatchling swims for a long time. It is thought that they find beds/rafts of sargassum algae to float around with. It is there that they begin to eat and grow.
Ernst, C. H.; Lovich, J.E. (2009). Turtles of the United States and Canada (2 ed.). JHU Press. ISBN 978-0-8018-9121-2.
Janzen, Fredric J (1994). “Climate change and temperature-dependent sex determination in reptiles” (PDF). Population Biology 91 (16): 7487–7490.
Lorne, Jacquelyn; Michael Salmon (2007). “Effects of exposure to artificial lighting on orientation of hatchling sea turtles on the beach and in the ocean” (PDF). Endangered Species Research 3: 23. doi:10.3354/esr003023.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
US Fish and WIldlife Service, North Florida Ecological Services, Olive Ridley Turtle Fact Sheet.
Witherington, Blair (2006). “Ancient Origins”. Sea Turtles – An Extraordinary Natural History of Some Uncommon Turtles. St Paul, Minnesota: MBI Publishing Company. ISBN 0-7603-2644-4.
Wynne, Kate; Schwartz, Malia (1999). Guide to Marine Mammals and Turtles of the U.S. Atlantic and Gulf of Mexico. illustrated by Garth Mix (2nd ed.). Rhode Island Sea Grant. ISBN 0-938412-43-4.
Description
The flatback is a medium-sized hard-shelled sea turtle. The body is flat. The carapace has a thin, oval shape, with large non-overlapping scutes. The carapace is olive gray with brown/yellow margins. The carapace is turned up at the edges. The plastron is pale yellow. The head and front flippers are gray. Each flipper has one claw.
Distribution
Flatback sea turtles are unique because they live their entire lives on the continental shelf north of the Australian continent. They never spend time in the open ocean. Beaches on small offshore islands are their most important nesting sites.
Habitat
Flatback sea turtles live all their life stages in the same location and habitat.
- Gently sloping, sandy beaches with broad intertidal platforms
- Coastal waters and bays
These turtles prefer shallow, soft-bottomed seabed habitats that are far from reefs. They rarely leave the shallow waters of the continental shelf and nest only in northern Australia. Flatback sea turtles are found in coastal waters. They are reported to spend long periods of time floating on the surface of the water basking in the sun.
Diet
The flatback turtle is mainly carnivorous, feeding on squid, sea cucumbers, soft corals and mollusks. Occasionally they will eat seaweed.
Life History
Flatback sea turtles, like all sea turtles, spend most of their lives in the water. In general, once sea turtles enter the water they never come back on land except to nest. Unlike other sea turtle species, this one never spends time in the open ocean.
BreedingWith many reptiles, size is a more reliable indicator of sexual maturity than age. This is the case with sea turtles. For example, it is thought that the flatback reaches sexual maturity sooner than the other species of sea turtle because their high-protein diet contributes to rapid growth.
NestingThe nesting season varies by location. It runs from October to February in Queensland’s Northern Territory, but may occur year round in northwestern Australia.
The females usually nest at night. When a female is ready to lay eggs, she crawls up on the beach. Most nests are dug on top of dunes or as high as possible on the beach. She digs the egg chamber with her back flippers. Flatbacks can nest up to four times in a season. The interval between each nesting is usually 15 days. An average of 50 eggs are laid in each clutch. The flatback lays larger eggs than the other sea turtle species.
Incubation and HatchingIncubation lasts from 45 to 75 days. Like most reptiles, the temperature at which an egg is incubated determines its sex. This is referred to as temperature dependent sex determination, or TSD.
Hatchlings usually emerge from the nest at night. After the little hatchlings dig their way out of the nest, they quickly orient and move towards the ocean. They use moonlight and starlight reflected from the surface of the water as a guide. Unlike other sea turtle hatchlings, these turtles do not swim out into the open ocean. They spend their entire lives in the shallow waters of the continental shelf.
Australian Government. 2009. EPBC Act List of Threatened Fauna. Accessed March 30, 2012.
“Flatback Sea Turtles, Natator depressus ~ MarineBio.org.” MarineBio Conservation Society. Web. Thursday, July 31, 2014.
IUCN Marine Turtle Specialist Group. Flatback Turtle: Natator depressus. Accessed March 30, 2012.
Pendoley, K.L.; Bell, C.D.; McCracken, R.; Ball, K.R.; Sherborne, J.; Oates, J.E.; Becker, P.; Vitenbergs, A.; Whittock, P.A. (2014). “Reproductive biology of the flatback turtle Natator depressus in Western Australia.” Endangered Species Research 23: 115-123.
Sea Turtle Conservancy. Species Fact Sheet: Flatback Sea Turtle (Online). Accessed March 30, 2012.
Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: Johns Hopkins University Press and Oakwood Arts. ISBN 0-8018-8007-6.
World Wildlife Fund. Flatback Turtle.