February 4, 2013
Endangered Hawksbill Sea Turtles Mating Patterns Revealed
Brett Smith for redOrbit.com - Your Universe Online
Many animals spend their lives living in remote or inaccessible areas of the planet, so understanding their various habits can require some ingenuity from the various scientists who study them.
According to the research team´s report in the newest edition of Molecular Ecology, DNA samples taken from female hawksbill turtles on Cousine Island, located several hundred miles northeast of Madagascar, show that the creatures mate once a season and store the male´s sperm for up to 75 days while using it to lay multiple nests on the beach.
"We now know much more about the mating system of this critically endangered species,” said lead researcher David Richardson, from UEA's school of Biological Sciences. “By looking at DNA samples from female turtles and their offspring, we can identify and count the number of breeding males involved. This would otherwise be impossible from observation alone because they live and mate in the water, often far out to sea.”
The researchers set out to determine if sexual selection played a role in the turtles´ mating habits. They wanted to see if the females used their capability for storing sperm as a means of selecting a mate.
According to a genetic analysis, over 90 percent of the sample population of females had offspring that were sired by a single male. The researchers also found that the fertilization success of males was consistent across all the nests laid by individual females during the breeding season.
Based on these results, the scientists concluded that female hawksbill turtles (Eretmochelys imbricata) store sperm after mating as a matter of efficiency and not selection.
"Our research also shows that, unlike in many other species, the females normally mate with just one male, they rarely re-mate within a season and they do not seem to be selecting specific 'better quality' males to mate with,” said Richardson.
The biologist added that his study´s results could be important with regard to biodiversity and conservation.
"It also lets us calculate how many different males contribute to the next generation of turtles, as well as giving an idea of how many adult males are out there, which we never see because they live out in the ocean,” he said. "Perhaps most importantly, it gives us a measure of how genetically viable the population is - despite all the hunting of this beautiful and enigmatic species over the last 100 years.”
Richardson noted that the study is a positive sign for this population of sea turtles.
"The good news is that each female is pairing up with a different male — which suggests that there are plenty of males out there,” he said. “This may be why we still see high levels of genetic variation in the population, which is crucial for its long term survival.”
“This is an excellent example of how studying DNA can reveal previously unknown aspects of species' life histories,” added co-author Karl Phillips, a PhD student in UEA's school of Biological Sciences.
"Understanding more about when and where they are mating is important because it will help conservationists target areas to focus their efforts on.”