CHARACTERISTIC COMPARISON. Green Turtle - Chelonia mydas

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1 5 CHARACTERISTIC COMPARISON Green Turtle - Chelonia mydas Green turtles average 1.2m to 1.4m in length, are between 120kg to 180kg in weight at full maturity and found in tropical and sub-tropical seas around the world. While floating the ocean currents the young turtles feed mainly on zooplankton such as fish fry and larval crustaceans of shrimp, crabs and lobsters. As they become older, their diet is mainly vegetarian eating marine algae, 'grasses' and mangrove leaves. They have also been seen to eat certain seajelly including the highly poisonous Box Jelly (Chironex fleckeri). Mature females usually nest five times each season, every five years. However, individuals can nest up to eleven times in one season, producing up to 1,200 eggs. Each nesting, they lay an average of 110 round, whitish eggs which have a rubbery parchment like shell. The average size is approximately 45mm diameter and weighs approximately 50gm. Thousands of Green turltes are slaughtered for their eggs and their flesh and today their numbers are severely depleted worldwide. Fortunately, there are still reasonable numbers in Australia.

2 6 LOGGERHEAD TURTLE - Caretta caretta Loggerheads are one of the largest sea turtles and are easily identified by their very large head. Loggerheads reach an average length of 95cm and weigh approximately 120kg. They are mainly carnivorous, eating crabs and other crustaceans, shellfish, sponges, seajelly and fish. They are found in coastal tropical and sub-tropical waters worldwide and have been recorded diving to 230 metres. Nesting occurs between October and February and mainly at night or in the late afternoon. The female digs a large hole in the sand with the hind flippers and lays approximately 120 whitish pink, round eggs about the size of a table tennis ball. They average 40mm in diameter and weigh approximately 40gm. She may repeat this three or four times a season. These turtles are still being harvested for food and large numbers are drowned in nets, thus making the Loggerhead an endangered species. It is quite possible that they will become extinct.

3 7 FLATBACK TURTLE - Chelonia depressa. The Flatback turtles are found in coastal waters off Northern Australia from the Kimberly region of Western Australia to Bundaberg, Queensland. They eat soft corals and other soft invertebrates. Their average length is 90cm and approximate weight is 72kg. Flatbacks in southern Queensland nest in the summer while further north, they are seen to nest all year round. They may nest anywhere between one and five years and will lay between one and four times during each season. Flatback turtles lay on average 50 eggs each nesting. The eggs are large, round, whitish in colour with a rubbery shell and average 52mm in diameter and 78gm in weight. Flatback hatchlings are about twice as big as Green turtle hatchlings and their incubation period is about eight weeks. The limited range of these animals means that they are greatly affected by human intrusion and change. Parks have been set up to protect breeding areas of the turtle.

4 8 HAWKSBILL - Eretmochelys imbricata. Hawksbill's are found worldwide in tropical and sub tropical seas. Their main diet consists of sponges but they have been seen to eat molluscs, sea jellies, sea squirts, sea urchins and fish. The Hawksbill has a narrow beak that is used to extract food from rock crevices and coral fissures. They average 84cm in length and weigh between 54.5kg. Females normally clutch three times each season and usually lay every two to three years. Hawksbills lay approximately 160 eggs each nesting. The eggs are round with a rubbery shell, which average 40mm in diameter and weigh approximately 40gm. The Hawksbill is the turtle famous for "tortoise-shell". Heat is applied to soften the keratinised plates of the carapace which are then removed whether the turtle is dead or alive. This species is still highly threatened and is seriously depleted in most parts of its range.

5 9 PACIFIC RIDLEY - Lepidochelys olivacea This turtle is also known as the Olive or Olive Ridley turtle. They are found in tropical waters of the Pacific, Indian and South Atlantic oceans averaging 65cm in length and 45.5kg in weight. They mainly eat small shrimp, sea jellies, small crabs, sea snails and fish. The Pacific Ridley has no specific season for nesting and the intervals between nesting varies immensely. They lay on average 110 eggs each nesting which are round, smallish (about table tennis ball size) with a rubbery parchment like shell. The Mexicans harvest this animal for its oil and also its skin for leather manufacture. However today, it is totally protected in those waters. This species, although the world's most abundant, is still threatened and becoming seriously depleted in some parts of its range.

6 10 KEMPS RIDLEY - Lepidochelys kempi Other Common Names: Atlantic Ridley North Atlantic Ridley Kemps Loggerhead Gulf Ridley Mexican Ridley Bastard Turtle These turtles are found in the tropical to sub-tropical waters around the North Atlantic Ocean and Gulf of Mexico. Their diet consists mainly of crabs as well as other crustaceans, sea jellies, molluscs, fish, sea stars and urchins. Their average length is 65cm and average weight is 45.5kg. The Kemps Ridley is the only marine turtle that usually nests during daylight hours. Nesting occurs mainly between 9.00 am and 1.00 pm in May and June. There are two to three clutches per year, however there is no regular interval between nestings. Individual females nest every one or two years. These are the turtles that use to nest in huge groups of up to 40,000 females, however now there are rarely even 1,000 animals nesting at the same time. Kemps Ridley only nests on Tamaulipas beach in Mexico and lays an average of 140 eggs each nesting. The eggs are round, about the size of a table tennis ball with a rubbery shell, weighing approximately 40gm. Due to massive over exploitation, the status of Kemps Ridley is critical.

7 11 LEATHERBACK TURTLE - Dermochelys coriacea This a pelagic turtle, wandering great distances in all tropical and sub-tropical seas feeding mainly on seajellies with some tunicates (sea squirts or cunjevoi). It is the world's largest marine turtle with old reports of them reaching up to 3m in length. However, they generally measure about metres and weigh between 365kg and 544kg and can often be 2 to 3 metres across from flipper tip to flipper tip. The Leatherback has a cartilagenous carapace covered in soft, smooth, relatively scaleless skin which is black, spotted with white or pink. Nests at night up to nine times per season with an interval of ten days between nestings. This is shorter than any other marine turtle. Breeding season is from March to July in the Northern Hemisphere and from October to February in the Southern Hemisphere. Females nest every two years laying approximately 90 eggs per clutch. The average size is about 51mm in diameter and weighing approximately 75gm. This turtle is in desperate need of urgent protection.