September 12, 2024

Participating in the NYK Kishu Minabe Loggerhead Turtle Survey (The Sea Turtle's Tears Speak)

　I had the opportunity to participate in a volunteer survey held in Minabe Town, Wakayama Prefecture, from July 21st (Sunday) for three days, supported by Nippon Yusen Kaisha (NYK Line) and
organized by the NPO Earthwatch Japan with the cooperation of the Japan Sea Turtle Association (Chairman: Yoshimasa Matsuzawa). I would like to report on my experience.

Volunteering is hard

After a lecture from Professor Matsuzawa on sea turtles and sea turtle conservation efforts in Minabe Town, we set off to assist in the survey that night. We split into two beach teams and headed out to sea to search for sea turtles that had landed. Our Chirihama team patrolled the approximately 1km stretch of Chirihama beach in hourly shifts from 8:00 PM to 2:00 AM. We walked along the beautiful beach under the full moon, searching for turtle footprints. On a sauna-like hot night, our feet got stuck in the soft sand. There was no time to enjoy the beautiful ocean; it was simply exhausting. On the first day, a team from another beach, Iwashirohama, successfully attached a transmitter to one turtle. Our Chirihama team found signs of a turtle landing. However, although it had landed, it apparently returned without laying eggs. It is speculated that it was frightened by train and car lights. It's a delicate species. On the second day, we were able to attach a transmitter to a new turtle at Iwashirohama. It is said that this individual may have returned from Chirihama on the first day without giving birth.

Being a mother loggerhead turtle is tough

Here's some information about loggerhead sea turtles that I learned from my teacher.
Loggerhead sea turtles (Caretta caretta)　are an endangered species, and their population has been declining drastically in recent years. They are omnivorous, but are carnivorous, mainly preferring benthic organisms (shellfish and crustaceans) (green sea turtles are herbivores, eating seaweed and seagrass). They have no gills and breathe with lungs, and can dive to depths of about 200m for 2 hours. Their lifespan is estimated to be 70 to 80 years. In the East China Sea, the increase in bottom trawling has reduced their food supply, and many individuals are forced to wander the ocean where food is scarce. Their natural enemies are orcas and sharks. Their nesting grounds in the North Pacific are Japan and Jeju Island, but no landings have been confirmed on Jeju Island since 2007. In Florida, marine plastic waste has been found in 93% of sea turtles. However, most of it is not digested and is excreted from their bodies. They are thought to possess a powerful geomagnetic compass and can navigate quite accurately by observing the position of the sun.

Apparently, the sex of sea turtles is determined by the temperature of their eggs. Males are born when the sand temperature is below 29°C, and females are born when it is above 30°C. As global warming progresses, only females will be born first, and at temperatures of 33°C, the eggs will die. Females prepare their eggs and can only ovulate after mating. I was shown a GPS track map of an individual that is presumed to be wandering around Osaka Bay, unable to find a male. It seems that the decline in males may have already begun. Recently, due to the worsening of ocean conditions, there are many cases where eggs are washed away by high tides and waves. The line of vegetation on the sandy beach is a marker to indicate where high waves will not reach. Mother turtles desperately try to climb the sand dunes to reach this point. I could hear their heavy breathing.
　
On average, sea turtles reach sexual maturity and become adults capable of reproduction at around 40 years old. The effects of current global warming will become significant in 40 years. I was surprised at how delicate their ecology is.

Besides this, modern times are full of trials and difficulties, such as artificial structures (for example, the construction of fishing ports) taking away sandy beaches, the problem of light pollution (hatchlings perceive the direction of light as the sea. They mistake the lights of trains, cars, and towns for the sea and swim in the opposite direction, dying. Mother turtles dislike the light and cannot come ashore), and getting entangled in fishing nets and drowning.
　
Sea turtles also play an important role in transporting nutrients from the sea to land. Realistically, even if only about half of the eggs hatch, the waste products used in the eggs and the eggs that do not hatch together make up about two-thirds of the total nutrients for land organisms. Sandy beaches are nutrient-poor environments. Turtles support this vegetation with nutrients, and plants play a major role in maintaining the sandy beaches. It was said that the stability of the sandy beaches is extremely important for both beach maintenance and the health of the ecosystem. Maintaining an ecosystem is a harsh reality. For all these reasons, even here in Minabe town, the number of sea turtles coming ashore and laying eggs has drastically decreased.

The bees are suffering too

Meanwhile, Minabe Town's "Minabe-Tanabe Plum System" has been registered as a Globally Important Agricultural Heritage System. Satoyama forests produce Kishu Binchotan charcoal, plum groves cultivate high-quality plums, and the town has abundant rice paddies, protecting the vegetation and environment behind the coast. Healthy agriculture and forestry are the town's core industries, and the town is being built without using sea turtles as a tourist attraction. The town office is understanding and supportive of sea turtle research, and the youth group is also active in providing support. It is a kind and wonderful town.

However, this year's plum harvest was the worst in recent years. The extremely warm winter apparently deactivated the honeybees responsible for pollination, and pollination did not progress at all. This raises concerns about the effects of global warming.

It's so hard to face such a delicious meal!

By the way, the food on this program is very, very delicious. However, with all this delicious food, there was no beer, so we ate our meals in about 30 minutes and headed off to work late into the night. We also had all-you-can-eat umeboshi, a specialty of Minabe!　

 Learning

The sea turtle research has no direct impact on our business or the economy. However, I know this may seem presumptuous, but I believe that what we have learned through basic biological research speaks to the reality of global environmental issues. There is still so much we do not know about the world around us. Through this sea turtle research, I was reminded once again of the many important realizations and lessons we have to learn. I feel that this type of research and research support is extremely important. I learned that ecosystems are delicate, and even a temperature change of 1 or 2 degrees can have a huge impact. Meanwhile, I learned that each transmitter attached to a sea turtle costs $4,000. I also learned that the labor and research costs for researchers and volunteers are significant. I sincerely hope that this Minabe loggerhead turtle research will continue, that research results will be produced and shared with the world, and that the NYK Group's support will continue. I hope that employees will participate again next year.

At the final seminar, we all gave names to the loggerhead turtles. Data from the transmitters will be tracked and stored under these names. The turtle that was born on the first day was named "Luna-chan" after the full moon night, and the turtle that had a transmitter attached on the second day was named "Tae-chan." There were shark bite marks on "Tae-chan's" shell, so the turtle was named after her for enduring the difficult journey and coming to lay eggs, as well as for enduring the process of having a transmitter attached after laying eggs.

Good luck, Luna-chan, Tae-chan and everyone at Minabe!

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