Six species of sea turtles nest and feed in the marine and coastal habitat of Western Australia: flatback, green, loggerhead, hawksbill, leatherback and olive ridley. Of these six, four species nest on islands and beaches of the northwest: flatback, green, loggerhead, hawksbill. All six species are in danger of extinction and are protected by state, Commonwealth and international laws and treaties.
Marine turtle nesting occurs from Shark Bay in the south (loggerheads) to the Kimberley and the border with the Northern Territory (flatbacks, greens, hawksbills). Nesting season varies by species and year, but generally nesting occurs from November to March with a peak in mid-summer -- December and January. In the Kimberley, flatback sea turtles are known to nest year-round with mid-summer peaks.
The Australian flatback turtle is the only marine turtle that nests exclusively in Australian territory. It is one of only two marine turtles not having a global distribution - the other being the Kemp's ridley in the Gulf of Mexico. Flatbacks dive deeper and longer than other sea turtles. Their eggs and hatchlings are as big as those of the mighty leatherback. And unlike other species that disappear deep into the ocean for years, flatbacks spend most of their life, if not all of it, in relatively nearshore waters. Yet so little is known about the flatbacks that they are designated "data deficient" by the International Union for the Conservation of Nature.
Photo by Dave and Fiona Harvey, EcoBeach near Broome.
Green sea turtle
Green turtles are the most common species seen in Western Australia. Between thousands to tens of thousands of females nest along the coast between October and February each year. The main nesting areas for green turtles in the Kimberley are at the Lacepede Islands, with smaller regionally important nesting stocks visiting Browse Island and Scott and Ashmore Reefs areas. The green turtle rookery on the Lacepede Islands is one of the largest remaining green turtle populations in the world. Tens of thousands of green sea turtles have been tagged in Western Australia over the past two decades, but the data has never been released. While these sea turtles appear to be abundant, they are in decline and threatened with extinction. The green sea turtles survived a commercial fishery along the northwest coast that existed until the 1970s that killed at least 60,000 animals. The nuclear bombing of the Montebello Islands destroyed about 5,000 animals, according to W. A. government estimates. Today, in Western Australia, populations are decreasing by about 6 percent per year.
Photo by Chris Pincetich of loggerhead in Hawaii.
The Western Australian loggerhead population is the third largest in the world and is one of only four stocks in the Indian Ocean, according to Limpus (December 2008). Most of the nesting occurs south of the Kimberley along the Ningaloo Coast and at Dirk Hartog Island, which remains unprotected habitat. Limpus estimated the number of breeding female loggerheads in Western Australia to be in the range of several thousand females. Ningaloo Turtle Program estimates the loggerhead turtle has lost 50-80% of its annual nesting population in the last decade.
Photo by Teri Shore at Mon Repos, Queensland.
Within the Indian Ocean-Western Pacific Ocean region, Australia supports the largest remaining stocks of breeding hawksbills, according to the Queensland EPA's biological review of the hawksbill. Within Australia, there is one distinct population in the northern Great Barrier Reef, Torres Strait and Arnhem Land and another that nests on the northwestern shelf of Western Australia. In WA, Rosemary Island in the Dampier Archipelago may support up to 1,000 nesting females annually, with other nesting sites perhaps collectively supporting another 1,000 nesting females annually. However, because there have been no long-term monitoring or tracking programs for the hawksbill in the region, it is not known whether these turtles are in decline or stable or otherwise.
Doug Perrine Photo/Seapics.com
The leatherback is the largest of all sea turtles, growing to over six feet in length and weighing over 2,000 lbs. Leatherbacks routinely swim great distances across ocean basins and can dive to depths greater than 3,000 ft. The Australian government in 2009 increased protections for the Pacific leatherback by listing it as endangered, strengthening its previous status as "vulnerable." The Pacific Leatherback sea turtle is occasionally sighted migrating through the Kimberley and Western Australian waters as far south as the Southwest corner of the state. On the east coast the leatherback has been tracked as far south as Tasmania. These leatherbacks, while probably low in number due to a 90 percent decline globally; can be found foraging in Australian waters throughout the year.
Doug Perrine Photo/Seapics.com
Olive Ridley Turtle
A rare olive ridley turtle was sighted nesting on the Dampier Peninsula in the Kimberley in 2008. More frequent nesting occurs in parts of the Northern Territory. Foraging olive ridleys have been spotted off the Kimberley and Exmouth coasts. More research is needed to determine the population and status of the olive ridley in the Kimberley and Western Australia.