INPEX CORPORATION (INPEX) has been supporting loggerhead sea turtle conservation research activities on Tanegashima Island in Kagoshima Prefecture through NPO Earthwatch Japan since 2025.
Tanegashima is the second-largest nesting site for loggerhead sea turtles in Japan. This year, the research activities were conducted over eight nights in June and involved a total of 48 participants, including INPEX employees and external volunteers.
The research activities have been conducted in Tanegashima since 2015 to determine whether loggerhead sea turtles return to Tanegashima Island to nest and to collect data on body size, remigration rates and population trends. The research aims to contribute to the conservation of loggerhead sea turtles and the preservation of healthy nesting environments along beaches.
In addition, as a new initiative introduced last year, GPS transmitters were attached to two loggerhead sea turtles to track their movements. This feature is expected to help gather more data on the loggerhead sea turtle habitat range and ecological characteristics during the non-nesting season.
Before the research activities, researchers and members of Turtle Crew, a local NPO, gave lectures on research methods to all participants. The research activities began at around 21:00 local time and involved searching for turtles coming ashore to nest. Once such turtles were located, participants checked and/or attached tags and measured their carapace in a manner that would not interfere with the nesting activity.
Two turtles were also affixed with GPS transmitters. This process was repeated until around 03:00 local time.
During the eight-night survey, researchers encountered 40 nesting turtles on a total of 49 occasions and confirmed 33 nesting sequences. Although the number of loggerhead turtles coming ashore on Tanegashima has generally remained relatively low in recent years, consistent with trends observed at nesting sites throughout Japan, encouraging results were obtained this year.
A total of 20 remigrated turtles previously identified on Tanegashima Island were recorded during the survey. This significantly exceeded the annual average of one to eight remigrated turtles observed over the past ten years. Remigrated turtles were particularly common during the first half of the survey period, with 12 of the 19 turtles recorded during the first two days (63.2 percent) identified as remigrated females. The increase in remigrated turtles may indicate improved survival rates during non-nesting periods and represents an important indicator for understanding the conservation status of loggerhead turtles.
Yoshimasa Matsuzawa, director of the Japan Sea Turtle Association and the project's principal researcher, said, "With INPEX's support, we are now in the second phase of the sea turtle identification and research program in Tanegashima. During the first phase, which lasted 10 years, we focused on exploring where and how to conduct the research activities along the coastline. In the second phase, we are conducting the activities in a quantitative manner. We are using GPS to track turtle movements and improve the accuracy of our research activities to identify the factors that determine which turtles are able to remigrate to nest and which are not."
INPEX will continue to contribute to biodiversity conservation and advance its sustainability management initiatives.
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Loggerhead sea turtle fitted with a GPS transmitter
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INPEX employees and local staff participating in the conservation research activities
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Location data obtained through GPS tracking of a loggerhead turtle
