London: Believe it or not, loggerhead turtles take almost half-a-century to grow up.
A new research by the University of Swansea has found that a female turtle will not start to lay eggs until she is 45 -- it`s the maturity age, the `Functional Ecology` journal reported in its latest edition.
This estimate, based on examination of several decades of data on the turtles` growth, has implications for conservation efforts, say researchers.
It reveals how long it takes for turtles hatched at a protected nesting site to return to that site to breed.
Prof Graeme Hays, who led the study, explained how reaching maturity so slowly meant that the turtle population was "less resilient" than previously thought.
"The longer an animal takes to reach maturity, the more vulnerable the population is to (man-made) causes of mortality," the `BBC` quoted Prof Hays as saying.
This, he explained, was because there was a much higher chance of an individual animal being killed -- for example, by being deliberately or accidentally caught in a fishing net
-- before it had been able to "replace itself" by breeding.
It is, however, extremely difficult to follow the life cycle of a sea turtle as they drift through thousands of kilometres of ocean, spending the vast majority of their time
"You can`t follow one individual throughout its life. So previous estimates of their age at maturity are all over the place -- spanning from 10 years to 35 years. It was impossible
to get some sort of consensus," Prof Hays said.
To overcome this problem, the researchers embarked on a three-part data trawl.
To estimate the growth rate of newly hatched turtles, the team examined measurements of hatchlings at a nesting site in Florida and compared these with the sizes of the same turtles when they had drifted across to the Azores islands in the middle of the North Atlantic.
This journey -- drifting several thousand kilometres on the currents -- takes approximately 450 days. The scientists were able to see from the data they examined how much the turtles grew during that time.
The team also used many hundreds of measurements made by scientists who had captured, marked and recaptured individual loggerhead turtles. Using these figures, they were able to chart the animals` growth rate.
All of this data enabled the researchers to use the size of mature loggerhead turtle mothers to estimate their ages.
Bryan Wallace, science adviser for Conservation International`s Sea Turtle Flagship Program, said: "These estimates reinforce that animals like sea turtles take a very
long time to recover from human-caused population declines."