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April 16, 2024

DNA explains hawksbill’s survival

By Alice Hung | February 7, 2013

Evolution may have finally caught up to one of the most magnificent and long-living creatures still existent in our world: turtles. These reptiles first made their appearance, as far as scientists agree today, approximately 220 million years ago. However, recently increasing numbers of species in the Testudines order are qualifying for the “Critically Endangered” and “Endangered” conservation statuses.

In 1996, the hawksbill sea turtle – know for its beautiful shell – made it to the critically endangered list. The waning of its population was primarily due to the international trade of turtle shells as a form of decoration, making the hawksbill a desirable species to hunt.

Throughout history, their gorgeous golden brown carapaces have been popularly used to make jewelry and other luxurious items. Fortunately, for the turtles and all turtle-lovers, this inhuman and meaningless practice was banned the same year hawksbills were labeled as critically endangered.

To understand more about these creatures and help them re-populate the seas again, scientists have been studying their mating patterns. David Richardson from the New University of Easy Anglia and his colleagues focused their efforts on Cousine Island of the Seychelles, the safe haven of most surviving hawksbills today. Using DNA collected from the nesting mother and her offspring, Richardson sought to learn about these turtles’ breeding habits.

The Seychelles hawksbill turtles typically breed between September and February. From the DNA samples collected, it was found that the mating occurs at the beginning of the season. Afterwards, females would store the deposited sperm for next few months, gradually dipping from the reservoir to support multiple nests.

When ready to lay, the female turtle lugs her body ashore to the drier areas of beaches during the night. She normally spends a few hours digging a hole that is large enough to support around 140 eggs. After safely burying the eggs, the mother quietly swims back into the ocean, never to return to her babies again. The babies hatch after two months. In the midst of the night, they make their way towards the ocean, where they live the rest of their lives.

A surprising discovery from this study of the DNA, according to the researchers, is that the hawksbills’ marital practice. Unlike other animals, hawksbill turtle females are monogamous.

Polygamy is common in the animal kingdom. Following Darwin’s doctrine, “survival of the fittest,” it is easy to understand why it would be advantageous to have multiple mates. After all, the more offspring an individual leaves behind, the greater the probability that at least one will be fit enough to survive and breed. As a result, the genes from said individual would be passed on. On the evolutionary scale, propagation of one’s genes is the most, if not the only, important task given to a living organism.

With this in mind, it is shocking to find that hawksbill turtles, and humans for that matter, defy this common pattern. With this information, scientists have been tracking and estimating the total number of adult males and their relative contribution to the newer generation of hawksbills.

In addition, it seems that each monogamous female chooses a different male with whom to breed. This would contribute to the genetic variation of the population – an advantage in terms of long-term survival.

Considering that the hawksbill sea turtles have admirably survived through the past 100 years of hunting practices, Richardson agreed that at least some of the success owes to their mating practices and maintenance of genetic diversity. With the collected DNA information, scientists hope to understand more about these critters and contribute to current conservation efforts.

With a ban on hawksbill hunting, an effort to understand more about them, and a strong desire from the rest of the population to save these amazing creatures, hopefully the hawksbill sea turtles will soon make it off the Critically Endangered list. After all, wouldn’t it be wonderful to see more of these beautiful creatures gliding through the oceans?


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