More About Them....
Adults – Growth is dictated by food supply so it is not possible to tell their age by size. Females are large and reach maturity when their carapace length is 160 - 170mm so as to hold the clutch of eggs (16 –25). They can grow to a shell length of up to 40cm with the head & neck equally long. Females weigh from 1-2 Kg. Males are smaller but have a longer tail and weigh up to 1 Kg. They are sexually mature when their carapace length is 140mm.
Hatchlings - Weigh about the same as a 10c coin. Their shells are initially soft but firm up over a few weeks once the turtle starts to eat. Hatchlings have a high mortality rate due to predation by birds (ravens, kookaburras), dogs, cats and foxes. The danger is when they are still in the nest and when they emerge in August, high above the winter rains water-line, and have to run to the safety of the pond or lake. Each clutch of eggs may only have one or two survive out of a dozen or more eggs laid by the mother in the spring. Some nests are completely destroyed soon after laying.
Time period : Stage
Winter-Spring : Mating
Spring-Summer : Nesting
Autumn-Winter : incubation 26-41 weeks
Winter-Spring : Hatching
It can take up to a year from mating in Winter & Spring, to egg laying in early Spring – Summer, to hatching at the end of Winter. Egg laden females are no match for a car and are often killed each year while crossing roads to reach nesting sites above the water level of winter rains. Injuries are life threatening and many die from damage to internal organs.
The long lives of turtles are often proclaimed as fact, but reliable evidence is lacking. if an individual survives to adulthood, it will likely have a life span of two to three decade. (Encyclopedia Britannica.) Turtles are said to live as long as humans but there is no data to support this claim. But, because of their perceived long life span they symbolize longevity in some cultures, such as China.
Oblong turtles are difficult to age as there are no growth rings on the shell. A turtle may grow quickly when food is available, or slowly during bust cycles when food is scarce so size is no indication of age. Sexual maturity is around 5 years but females grow much larger than the males in order to store fat for egg yolk production and house the 2-16 elliptical eggs.
200 million years in the making has resulted in one of the most cleverly complex creatures on earth – the not-so-humble turtle. Turtles evolved in the Triassic period, when dinosaurs were beginning to walk the earth, and have changed very little since then. They are highly adapted to their environment and have many special features including ballast tanks similar to a submarine, for regulating flotation, large lungs that are also used for flotation as well as breathing, a complex heart that can shunt blood away from the lungs completely when submerged for long periods, and a neck as long as its oblong shell with nostrils arranged like a snorkel. These little animals had their submarine skills, including sonar, perfected thousands of years ago. It’s taken mankind until the 20th century to develop modern submarines (at vast cost, utilising nuclear power and large
operating crews) which come close to replicating the natural abilities of a turtle.
Interestingly the first true submarine which was built during the American Revolutionary War was called, appropriately, Turtle.