The 7 sea turtles of the world
Sea turtles are one of the Earth's most ancient creatures.
There are seven recognised species of sea turtle surviving today:
- green turtle (Chelonia mydas)
- loggerhead (Caretta caretta)
- flatback (Natator depressus)
- hawksbill (Eretmochelys imbricata)
- leatherback (Dermochelys coriacea)
- olive ridley (Lepidochelys olivacea)
- kemp's ridley (Lepidochelys kempii).
All but the kemp’s ridley turtle are found in Australian waters. The main species nesting on Sunshine Coast beaches are the loggerhead turtle and, less frequently, the green turtle.
It is often lamented among ecologists and environmental scientists that it is only the 'charismatic megafauna' that people feel compelled to protect. Whales, fur seal pups and pandas, to name a few, are much more likely to be the subjects of passionate widely circulated petitions than say, a minute foundation species of phytoplankton that actually underpins an entire marine ecosystem.
While hopefully this imbalance will be addressed as ecological education improves, it is in the meantime fortunate for the sea turtles that they fit into the 'charismatic megafauna' category. Watching any species of sea turtle lumber up a beach and undertake the laborious task of digging a nest is almost guaranteed to activate that protective instinct in anyone. If he or she is also lucky enough to witness a nest emerging then you have probably converted that person to a lifetime of interest in the species.
Paradoxically, despite the esteem in which we hold them and the effort we put in to saving them, human activity is without doubt the reason that 6 of the 7 species are currently listed as 'endangered' under most international, national or state legislation.
Sea turtles represent ancestral reptiles that originally were adapted for life on the land and later, over 100 million years ago, returned to a life in the ocean. Over time a number of adaptations occurred to allow sea turtles to spend almost their entire lives at sea.
Sea turtles spend almost all their lives submerged in the ocean but must come to the surface to breathe. Their lungs are adapted for rapid exchange of oxygen, which reduces the amount of time they need to spend at the surface. The blood of sea turtles can deliver oxygen efficiently to body tissues even at the pressures encountered during diving. During routine activity green and loggerhead turtles dive for about 4 to 5 minutes and surface to breathe for 1 to 3 seconds. A female loggerhead tracked at sea made up to 500 dives in a 12 hours period.
The limbs of their terrestrial ancestors would have been entirely unsuitable for an aquatic existence so over time sea turtles have evolved with modified forelimbs to help them move through the water. Rear flippers assist with propulsion, particularly by hatchlings and juveniles in the pelagic stage. The rear flippers are also are used by females to dig the egg chamber after she has excavated a nest area with her front flippers.
Like all other animals, sea turtles need freshwater to survive. The tendency of sea turtles to lose water to the surrounding ocean is decreased by their skin and shell being highly resistant to water diffusion and their ability to drink seawater. People have often commented that they have seen female turtles 'crying' as they were laying eggs. The 'tears' that they appeared to be seeing were actually salt secretions released from special glands which excrete the excess salt taken up when drinking seawater.
On this website we will endeavour to bring you information that will not only sustain your interest in what are indeed examples of charismatic megafauna, but also provide information and links to research that will ignite a passion to protect all species in the marine environment.