Rise in number of female turtles
Warmer weather is responsible for a growing number of female turtles.
Anne Meylan, scientific director for the Bermuda Turtle Project, confirmed that the number of female turtles has increased.
Preliminary results have suggested increasing feminisation,” Dr Meylan said.
“The final results for a longer time-series and complete statistical analysis will be available soon.”
A study in Australia, published in Current Biology, found that 99 per cent of immature green turtles born in the northern part of the Great Barrier Reef were female.
A total of 87 per cent of adult turtles found on the same section of the reef were female.
Between 65 and 69 per cent of turtles are female in southern areas.
Scientists have suggested that the difference may be the result of rising temperatures at the nesting sites.
The gender of a turtle is determined by its nesting environment, with warmer sand resulting in more female turtles.
If the sand temperature is higher than 84.7F, female turtles only will hatch.
It is not known what proportion of turtles need to be male to maintain a population.
Scientists said the effects of temperature changes may not be felt for decades as green turtles take more than 30 years to reach sexual maturity.
The study said: “While rising temperatures may initially result in increased female population sizes, the lack of male turtles will eventually impact the overall fertility of females in the population.”
Dr Meylan said that the increasing feminisation of sea turtles is a matter of global concern.
She explained that when turtles are caught for the Bermuda Turtle Project, blood samples are taken to determine the animal's gender.
Genetic testing has linked Bermuda turtles to nesting sites in Florida, Cuba and either Surinam in South America or Aves Island, a Caribbean island administered by Venezuela.