CMU SDGs

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Tracking the sea wanderer Leatherback sea turtle population studies

Views : 2171 | 03 Aug 2022
SDGs:
9 14 17

     Leatherback sea turtles are known for their incredible long-distance travels, often swimming across oceans for thousands of kilometres. It is therefore not a surprise that turtles hatched on the shores of the Gulf of Thailand have been spotted in Indonesia and other far flung locales. What is always astounding, however, is that they always return home to the beach on which they were born to hatch their eggs.

      A number of leatherback sea turtles travelled to Phang Nga and Phuket Provinces between 2018 - 2021 to lay eggs, bringing back hope that was growing bleak after having found no return of the turtles for the previous five years. As an endangered species, the leatherback turtle is protected by the Wildlife Preservation and Protection Act (1992), categorised as reptiles, due to their dwindling population.
Today there are very few leatherback turtles due in most part to their hereditary features which creates limited biological diversity, which limits breeding numbers. Not only that, the survival rate of a new born leatherback turtle is very low, with only the strongest two to three turtles out of every one hundred likely to survive.

The 14th nest of leatherback sea turtles (photograph from https://km.dmcr.go.th/)

     Once the few make it to the sea, therein lies further dangers, from ship propellers to fishnets and sea predators. Unlike whales or dugongs, which can be spotted by air, leatherback sea turtles’ populations are hard to quantify because once they are at sea, there is no way to know how many survive for how long.

    Leatherback turtles in Thailand lay their eggs in only two provinces – Phang Nga and Phuket. In the past 50 years, records show that the numbers of nests have been reduced by 95% due to the development of tourism in these areas. Today there are an estimated ten female turtles who lay eggs in the area laying between 10 - 20 nests. In the past, this number was as high a 250 - 300 nests.

Leatherback sea turtle eggs

      Between 2018 - 2021, however, the surge in numbers of new nests, numbering over 20, led researchers to speculate that it was due to the Covid-19 pandemic’s effects on tourism, which halted much of the human activities in the area, allowing nature to revive herself.

      In the past the Department of Marine and Coastal Resources took care of the wellbeing of the nesting turtles, with strict rules and regulations regarding their care from the moment they arrive on the shore to the moment the new born turtles first enter the sea. However, the research teams of the Phuket Marine Biological Centre and the Department of Marine and Coastal Resources were determined to find out more about the population numbers of the sea turtle, specifically the number of egg-laying female turtles between 2018 - 2020. This was because female turtles can nest more than once, therefore it was imperative to find out the actual numbers of egg-laying female turtles, to be used to estimate the numbers of sea turtles in the area. Thus began the joint research by the Phuket Marine Biological Centre, the Department of Marine and Coastal Resources, the Ministry of Natural Resources and Environment and Chiang Mai University’s Faculty of Veterinary Medicine’s Department of Veterinary Bioscience and Veterinary Public Health.

Location on a beach of a nest

     To that end, Professor Dr. Korakot Nganvongpanit, Dean of the Faculty of Veterinary Medicine Chiang Mai University, took 149 tissue samples from turtles which died in 14 nests from five beaches between 2018 - 2020 to analyse. It was found that all 14 nests were produced by three female turtles, as explained by Dr. Korakot;

     “In one nest there could be between 60 - 100 eggs, each with genes from both parents. Since female leatherback sea turtles breed with many males, we will only look at the genes inherited from their mothers, comparing genetics from nest to nest. Once all 14 nests were studied, it was discovered that there were only three different genetic varieties, leading researchers to surmise that all 20 nests came from only three female turtles.”



Example of a research subject

     This low number is of great concern as with fewer turtles breeding, the gene pool becomes even more limited. This could lead to inbreeding and many diseases which could lead to extinction.

Professor Dr. Korakot Nganvongpanit
Dean of Faculty of Veterinary Medicine, Chiang Mai University

    The crisis of the turtle population is of great concern and conservation must be instilled to protect this rare species. Awareness must be raised about eating or trading in turtle and the harm it causes. Beaches where turtles breed must be kept clear of noise and pollution. Plastic use and discarding in the sea must be limited or banned, as many sea turtles are strangled or suffocated by plastic waste. And any persons who violate such laws must be punished, with penalties of trading, possessing or hunting of sea turtles not exceeding 15 years in jail and a fine of no more than 1.5 million baht.


In spite of the many secrets which the leatherback turtles keep deep in the oceans, thanks to research done on population and breeding, some information is being gleaned and that information is warning us to care for our natural environment and to help protect our most vulnerable so that they may have a bright future.

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