University of East Anglia research has found that female hawkbill turtles normally mate just once at the beginning of the season and store sperm for up to 75 days to use when laying multiple nests on beaches.
They are also mainly monogamous and don't tend to re-mate during the season, the researchers said.
"Our research ... 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," biologist David Richardson said.
The hawksbill turtle was listed as critically endangered in 1996 by the International Union for Conservation of Nature because of a significant reductions in their numbers driven by the international trade in tortoiseshell as a decorative material, a trade now banned.
Because the turtles live underwater and often far out to sea, little has been understood about their breeding habits until the new study that used DNA samples from female turtles on Cousine Island in the Seychelles.
"Understanding more about when and where they are mating is important because it will help conservationists target areas to focus their efforts on," Richardson said.
"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."