AUSTRALIAN BIODIVERSITY RECORD - Calodema

Australian Biodiversity Record, 2007 (7): 1-90Description: This is the largest of the sea turtles, growing to 3 metres in length and weighingupwards of a tonne, although a large one nowadays would only be about 2 m and around 500kg in weight, with the average size now being only around 1.6m. and a couple of hundred kg.This species is immediately identifiable by the prominent longitudinal ridges along thecarapace (7) and plastron (4). The carapace has a thick leathery skin over the osteoderms.Mature colouration is usually very dark brown to black - tending to be darkest in agedspecimens. Sometimes individuals are encountered with varying degrees of pale cream oryellow spotting or blotching on the carapace also. When such specimens are out of the water,this pale spotting has been observed to change to pinkish as blood flows to the surface tocool the body. The plastron is usually whitish, sometimes pinkish also - presumably for thesame reason as the temperature-related changes to the dorsal spotting. The hatchlings are adeep bluish-black, with creamish white edging to the flippers and body. On the carapace theenlarged osteodermal ridges are white giving a lined appearance in some also. The throatand under-surface of the neck is bright white, with scattered black flecking. The forelimbs arevery large and paddle-shaped, lack webbing and are clawless.Distribution: Leathery Turtles are found throughout the oceans of the world having the largestdistribution of any sea turtle. In the Northern Hemisphere, they extend to the extreme latitudesof Alaska, Labrador, Iceland, the British Isles, and along the north sea coast of Europe. In theSouthern Hemisphere, they range as far down as the Cape of Good Hope, New Zealand,Argentina, Chile, and Australia. Leatherback Turtles also occur right across south-east Asia,into most African waters and throughout both the southern and northern parts of the AtlanticOcean, as well as throughout the Pacific and Indian Oceans. Leatherbacks have beenrecorded right around Australia, and have been regularly reported off the coasts of New SouthWales and Queensland, but less often in the waters of Victoria, Tasmania, South Australia,Western Australia, and the Northern Territory. The only nesting areas in Australia for thisspecies are located along central coastal Queensland, within about 20 km of Bundaberg, anda small area of north-eastern New South Wales near Ballina.Habitat: This is a pelagic species that may be found in coastal or continental waters as well asthe open ocean. It drifts with ocean currents well into the cooler latitudes, such as the colderwaters of Tasmania. It may be found in tropical, subtropical, temperate and even borealwaters. They are often observed at the mouths of rivers, and sheltered bays and inlets wherethey hunt jellyfish. Although Leathery Turtles are likely to occur in all our waters, both tropicaland temperate, they seem to be more often reported from the warmer areas of subtropicalsouthern Qld and northern NSW.Biology/Ecology: Leatherback Turtles have an advanced form of counter-current heatexchange within its body that allows it to have a core temperature some 18C higher than thesurrounding water. This physiological adaptation allows this species to occupy much colderareas of the world than other turtles, and similarly to keep cool in areas of warmer habitat. Itscapacity to exist across much of the world’s marine environment is a consequence of its largesize, high metabolic rate, thick fat deposits, and advanced circulation physiology. Thereproductive biology has received considerable attention but there is still much to be learntabout this very secretive species. It is known to make vast reproductive migrations from itsfeeding areas to its reproductive areas - like other sea turtles - although no Leatherbacks bornin Australia have been found as yet in other countries. A specimen marked as a hatchling inIndonesia has however been found in Western Australia, highlighting the potential importanceof protecting this species extralimitally. The main nesting beaches for this species around theworld are located in tropical and subtropical areas. It nests sporadically in Papua New Guineaand the Solomon Islands, as well as through various countries in south-east Asia - althoughthe once spectacular Malaysian nesting grounds have now collapsed and are almost ceasedto exist. The nesting areas of southern Java have almost been totally destroyed by overexploitationas has occurred in Borneo. A slight resurgence of nesting has occurred in parts ofSouth Africa, but only a handful of nestings occur annually there at present. An importantrefuge for the species is Natal, while western Mexico, Panama, Surinam, and French Guianaremain the major nesting areas for this species continued survival. Australia is however, onlyrarely used for nesting with perhaps only 1 to 3 nests per year being recorded fromQueensland and the Northern Territory. A rare nesting has been recently recorded from17