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Species Name: Careta Careta
National Listing: Endangered
Queensland Listed: Endangered
Western Australia Listed: Specially Protected Fauna All marine turtles are experiencing serious threats to their survival. The main threats are pollution and changes to their habitats, particularly their nesting sites, seagrass beds, coral reefs and mangrove forests. Other threats include accidental drowning in fishing gear, over harvesting of turtles and eggs; and predation of eggs and hatchlings by foxes, feral pigs, dogs and goannas. In Australia, all species are protected under various State and Territory legislation and the Commonwealth National Parks and Wildlife Conservation Act 1975 and due to the increasing threats, five of the six Australian water species are listed under the Commonwealth’s Endangered Species Protection Act, 1992. The Loggerhead turtle is currently listed as Endangered under this Act meaning it may become extinct if the threats to its survival continue. Based on information collected along the East coast, the Loggerhead turtle has lost 50-80% of its annual nesting population in the last 10 years. This information has raised severe concerns for the survival of the species worldwide. Back to the top
Identification Features
The Loggerhead turtle can be identified by the shape and markings on the shell and head. The Loggerhead turtle was actually given its name due to its proportionately large head, and the beak-like mouth used to shear and crush food. From the diagrams below, you can also easily identify the 5 pairs of large scales (Coastal scales) on each side of the shell. Loggerheads are the only species in Australian waters that have 5 pairs.
The red-brown to brown-black colour of the shell (Carapace) is also a distinguishing feature. How big and how old?
Adult Loggerheads can grow up to 1.5m long and weigh over 150kg making them one of the largest turtle species in the world. And to reach these proportions, it may take 60-80 years with a maximum age of 100 years a possibility!
And for a turtle to reach sexual maturity, they need to live at least 35-40 years and be 90cm in length. That’s a long time to mature into a reproductive adult raising concerns for the survival of the species. What do they eat?
They are mainly carnivorous feeding on fish, molluscs, sponges and jellyfish however they also mix their diet to include plant matter (seagrasses and algae).
With good eyesight, they can easily find and chase their food.
The juveniles in this tank are also ferocious carnivores devouring anything edible. For the first few years of their life they simply drift around in the currents alongside their food source, plankton. Feeding at will, they share their food with birds, fish and even the largest of all animals, the whales! Once they have reached a certain size (10-60cm), they return back to the coastal areas where they may live for many years until sexual maturity. How do they breathe?
Like all reptiles, these turtles breathe air at the surface. Between each dive, the turtles will poke their heads out of the water and take in a few deep breaths. They can actually hold their breath for up to an hour at a time. Like us, they have 2 nostrils on the end of their heads which close tight while under the water. They have very large lung capacity for long and deep dives often seen swimming and sleeping in excess of 50m. Do turtles sleep?
Loggerhead turtles spend a great deal of their day foraging for food and rest in short periods. However at night, each turtle will return to the seabed where it will snooze until morning. In fact, each turtle has its own sleeping area, which it will return to every night. Every hour or so, they slowly swim to the surface to take a deep breath. Back to the top
When and where?
In Western Australia, Loggerhead turtles nest on the NW Coast between Dec – April. Loggerhead turtles spend most of their first 30-40 years in one place feeding and sleeping. However, once they reach sexual maturity they are ready to make the long breeding migration of up to 3000km from their feeding grounds. Many tagged turtles have been recorded in Indonesia and the Northern Territory. Each breeding season, nesting females return to the same beach where they were born, to lay their eggs. As hatchlings, it is believed they may become imprinted to the Earth’s magnetic field and, possibly, the smell of the waters adjacent to the nesting beach. How many eggs, and how often?
Courtship and mating take place in the shallow water near the nesting site. A female will often mate with more than one male increasing her chances of fertilization. She will also lay up to 6 clutches of eggs at 2 weekly intervals. Considering each clutch averages 100 (ping pong ball size) eggs each, that’s a lot of egg laying! Each female will repeat this process for 20-30 years, although there may be intervals between breeding of 2-7 years. How do they lay their eggs?
When ready, the females crawl onto the beach above the high tide mark. This can be 100’s of metres taking several hours. She then digs a large hole with her hind flippers before laying the eggs. Finally, after covering the pit with the sand she returns back to the water. Many turtles often don’t make it back to the water, dying from stress and exhaustion. How do the turtles survive out of the water for so long?
The female will only nest at night avoiding the harshness of the sun. To get caught on the beach during daylight hours almost guarantees dehydration and death. They also minimise their travelling time up the beach by coming ashore an hour before high tide with the expectation of returning an hour after. They protect their eyes from both drying out, and damage from the sand by producing a constant flow of salt tears. This salt level is maintained through the drinking of salt water prior to landing on the beach. Back to the top
Incubation and hatching!
Incubation time and sex of the hatchlings depends on the temperature of the sand. Warm, dark sand produces mostly females and takes 7-8 weeks. Eggs laid in cool, white sand results in males who take longer to hatch. Therefore every turtle from every clutch laid around the same time in the same area will be the same sex!! What happens after hatching?
The hatchlings will take a few days to dig themselves out of the pit, often waiting until after dark before attempting the mad dash for the water. All the hatchlings attempt the journey together increasing their chances of survival. Unfortunately, their chances are minimal, as they are a favourite food source for birds, goannas, feral pigs, crabs, fish and sharks. In fact, they only have a 1 in 200 chance of reaching sexual maturity! Where do they go?
Little is known about the first few years of a marine turtle's life. They do keep on swimming away from the coast eventually reaching the deeper oceanic currents. They are considered to spend most of their time drifting along these currents feeding on the surrounding plankton. After a few years, they return to the feeding grounds of the coast spending 10-20 years in this area before becoming sexually mature. From then, they begin their migrations to where it all began, their breeding grounds. What research is being done?
Detailed research, population modelling and turtle tagging activities are being carried out in Australia and the Indo-Pacific region to assist with turtle conservation programs.
During summer at selected turtle breeding areas, each nesting marine turtle is tagged with a non-corrosive metal tag carrying an identification number. Later re-captures allow scientists to monitor populations, migration patterns, breeding activity, growth and mortality factors.
Genetic studies help to identify separate breeding populations and which population a particular turtle comes from, especially those captured at distant feeding grounds. Back to the top
Why are they at the Dolphin Discovery Centre?
The little Loggerheads found in the tank have had a tough few months. They are no older than 3-4 months and more than 1000km from home. They were travelling quite happily in Western Australia’s unique Leeuwin current feeding on the thick planktonic soup when a number of cold fronts from the Antarctic blew them off course and into the colder waters of the SW region. Weak and unable to catch food, the turtles were eventually washed ashore on the beaches around Bunbury. Luckily, these turtles were found in a relatively good state of health and were brought to the Dolphin Discovery Centre for rehabilitation. What are their chances of surviving?
As long as they are feeding, these turtles have a good chance of surviving the next few months in the aquarium. The temperature in the tank has been set at 22 degrees, they are given fresh prawns everyday, and they have absolutely no predators to worry about. How long will they stay and where will they go?
In the condition they are in, it will take 2-3 months before they are ready to be released. Once they have reached a satisfactory condition, they will be transported back up to Shark Bay where they will all be returned back into the ocean. Who sponsors this rehabilitation project?
Thanks to the Lotteries Commission of Western Australia, the Dolphin Discovery Centre was able to purchase all the aquarium equipment needed. This project is also under the guidance and support of the Department of Conservation And Land Management. You can help!
A small gold coin donation placed in the donation box at the Centre's entrance will go a long way towards maintaining the aquariums and the service required to continue this project. Any assistance will be greatly appreciated. Back to the top
Why are turtles so important to the indigenous community?
Marine turtles have important cultural and social values for Aboriginal and Torres Strait Islanders living along the coast of WA. Firstly, they are an essential food item for many of the island and NW coastal communities where there are few other sources of fresh meat. The eggs of Marine turtles are also an important source of protein. Green turtles are hunted more regularly than Loggerhead turtles because of their superior eating quality. Most turtles are taken during the breeding season.
Turtles are also a critical part of any major feast or ceremony. Marriages, birthdays, initiations and funerals are all examples of events requiring turtle for many indigenous communities. Are the turtles used for purposes other than food?
There are a number of other uses for turtle. The most obvious would be the use of the shell as a tool, a water carrier, food storage container, as a defensive weapon, sharpened for cutting and spear heads and as a fine piece of jewellery.
Turtle oil was also very popular as a medicine or tonic.
As a community, the capture of the turtles was also an opportunity to share a sense of good will, love and gratitude. Harvested turtles and eggs were always shared equally amongst relatives and friends of the hunters as gifts. What roles do indigenous communities play in research and management?
Indigenous communities promote the results of research carried out by a number of research and management organisations. They regulate access and numbers of turtles taken in traditional hunting grounds as well as monitor the harvesting activities to help effectively plan for the sustainable use of marine turtles. Back to the top
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