DIVE LOG Australasia

Keeping the sea Sponges under control

following the light of the moon and its reflection off the ocean, human interference can be strong at the beach, intentional or not. This can often cause hatchlings to crawl towards the lights of urban development and away from the relative safety of the ocean. The downhill slope of most beaches mean that turtles are more likely to head to the ocean than bright car headlights or restaurants. Scientists and Rangers around the world have set up programs to help the hatchlings at least reach the sea. Once they reach the ocean, it is goodbye to the beach for at least 20, maybe up to 50 years, until the female reaches sexual maturity. For now, they are at the mercy of the ocean. During their frantic dash to the water, a turtle’s brain starts to set up a type of mental GPS system, detecting the Earth’s magnetic field and allowing them to orientate themselves. It is this amazing adaption that allows them to find their way back to the beach all those years later. Unfortunately for turtles, only one in a thousand will survive to adulthood due to human impacts or predation. In some places, the eggs are removed from the nests and incubated in a secure environment, releasing the hatchlings when they hatch out on the same beach and allowing them to orientate themselves,hopefully increasing their chances of survival. This is a work in progress though as some research suggests that this mental GPS system is established during their time in the egg, so if they are removed from their nests, they may not get the correct

orientation and may get lost in the future. The initial years after hatching are called the ‘lost years’ and, as expected, very little is known about what happens during this time. It is thought that they mainly stay in the open ocean, using sargassum clumps as safety rafts until they grow to the size of a dinner plate. Many governments and organisations around the world have projects dedicated to tracking these young turtles with trackers that they attach on the beach before releasing them. For males, reaching the water is the end of the connection to their beach and the only reason they are normally found in coastal waters is to look for a mate, but the same cannot be said for females. Green turtles love to travel. The species is spread around the equator popping up in over 80 different countries. They get their name from their greenish flesh as they eat mostly seagrass and algae which is most often found in the shallow waters. Turtles also have a great sense of vision, smell and hearing which is very useful for not only finding food but also in finding love. After the ‘lost years’, female turtles will start to return to coastal waters to look for just this. It is at this time that she has reached sexual maturity and is ready to return to her beach. Every two to five years, the females will return to their birthplace and nest either on the exact beach they were born, or very close. The journey could be long as they will often explore the coast, only returning

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DIVE LOG Australasia #408 - October ‘24

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