Dugongs Found in Okinawa Prefecture
Researchers have found evidence that dugongs, an endangered marine mammal, inhabit broad areas of the Ryukyu Island chain in Okinawa Prefecture. This assessment was based on DNA analysis of fecal matter, a relatively new field of study.
The research team, which included members from the Incorporated Foundation Okinawa Prefecture Environment Science Center, Ryukoku University, and Kyoto University, also confirmed the presence of dugongs in the Miyako Islands for the first time in about 50 years.
However, the team stressed that the dugong population in the region is extremely small and needs further study. They also called for measures to preserve seagrass beds, which are the dugong's primary food source.
The dugong, which is believed to be the inspiration for ancient seafaring tales of mermaids, is a mammal that feeds mostly on seagrass. The waters around Japan's southwestern Nansei Islands, much of which lie in Okinawa Prefecture, are believed to be the northern limit of the dugong's habitat in the Pacific.
The dugong population in the region has been declining since the Meiji Era (1868-1912) due to overhunting for their fatty meat. The International Union for Conservation of Nature and Natural Resources designated the dugong subpopulation in the Nansei Islands as "critically endangered" in 2019.
Some experts believed the species might have died out in the Nansei Islands due to a lack of sightings after a dead female was found off Nakijin on the main Okinawa island in 2019.
However, the research team's analysis of animal feces found DNA sequences specific to the dugong in waters off Irabujima island in June and August 2022 and off the Kushi district of Nago in July 2022.
Combined with the geographical distribution of 66 dugong sightings and 26 feeding trails confirmed between 2010 and 2023, the researchers concluded that dugongs likely inhabit broad marine areas around the main Okinawa island as well as the Miyako Islands and Yaeyama Islands.
"Fecal DNA analysis is a new study method that provides more reliable scientific evidence than sightings and feeding trails," said Hiroyuki Ozawa, head of Okinawa Prefecture Environment Science Center's general environment research institute. "We hope to further specify the geographical distribution of dugongs to unravel their ecology."
The research results were published in the journal Scientific Reports.