DIVE LOG Australasia

eggs in thousands of holes in the sand. This takes one to two hours.They dig these holes using their hind flippers. They have been observed to display mating induced ovulation. That is after they mate, the female releases eggs. Females can store sperm, She often mates with several different males. Competing males will bite the flippers of a mating male and can inflict serious damage. It is most distracting and painful for the suitor. At Mon repos in Bundaberg, Green Turtle female and a Loggerhead mated in 1990 and produced offspring. One known inter bred turtle died at 29 years old and the other two were infertile. Research by Couper and Fitzsimmons tells us that all six species have interbred in the wild. Most commonly Hawksbill and Loggerheads to develop some fertile offspring. LIFE CYCLE Soft leathery eggs are laid in clutches in a

Dive instructor, Emma Louise, observes a massive female Loggerhead turtle showing the huge head. Byron Bay.

I was diving 70 Nautical miles off Bundaberg in January. As I entered the water for the night dive in the late twilight, I saw more than twenty new born Loggerhead turtles over the first five minutes swimming frantically close to the surface. I captured one and was amazed to feel how soft its carapace was. Otherwise, it was a perfect miniature turtle, hell bent on distancing itself from Mon Repos beach south of Bundaberg where it had hatched a day or two earlier. Loggerheads live in the open ocean until they reach juvenile age, and then they migrate to near shore waters after five years before returning to thier place of birth. BARNACLES Turtles develop growths on the carapace including dense foliage of alga and barnacles. If you thought about removing barnacles from a turtle to save it, it would cause

nest. The loggerhead’s sex is dictated by the temperature of the underground nest. Incubation temperatures generally range from 26–32°C. Eggs kept at a constant incubating temperature of 32°C become females. Eggs incubating at 28°C become males. An incubation temperature of 30°C results in an equal ratio of male to female hatchlings. Hatchlings in the centre of the clutch tend to be the largest, grow the fastest, and be the most active during the first few days of sea life. Hatchlings dig through the sand to the surface after incubating for 11 to 12 weeks. They hatch at night to increase the chance of escaping predation and avoid getting baked in the hot January sun. Hatchlings swim toward the ocean’s brighter horizon created by moon and starlights off the water’s surface. They swim for about 20 hours, taking them far out to sea. They can detect Earth’s magnetic field using Iron mineral Magnetite. This is called ‘The mad rush’

Hawksbill turtles captivate divers with their friendly behaviour.

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DIVE LOG Australasia #408 - October ‘24

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