"Okinawa is a fascinating place, and the dugong is revered there," Galvin said.
Historic dugong population numbers are difficult to come by.
But based on the ubiquitous presence of the animals in Okinawan lore, wildlife groups estimate that thousands—if not tens of thousands—swam near the island about 300 years ago.
Like their manatee cousins, the gentle giants forage on sea grass, growing up to 10 feet (3 meters) long and packing on more than 1,000 pounds (454 kilograms).
While large sharks and saltwater crocodiles have been known to prey on dugongs, cases of predation are rare, making humans the most likely culprits in the dugong decline.
For decades the animals have been tangled in fishing nets, have had their habitat filled in for development projects, and have seen their food disappear under silt-filled runoff from eroded soils, conservationists say.
As part of their efforts to protect the dugong, the Center for Biological Diversity has been leading a lawsuit against the U.S. Department of Defense.
The U.S. military has maintained a strong presence in Okinawa since World War II, with more than 30,000 personnel currently stationed on the island.
The lawsuit addresses a planned relocation of the Marine Corps' Futenma Airbase, which sits in a densely populated site, to a more isolated stretch of shoreline in Camp Schwab, according to the U.S. military.
But the project requires expanding runways into a bay that "is the richest area of sea grass in Okinawa," Galvin said. "It's the best of the last habitat for the dugong."
Marine Corps spokesperson Garron Garn in Okinawa said via email that the expansion project is designed to meet the military unit's operational needs.
The "exact location of the airfield was determined by higher authorities in the U.S. and Japanese governments," he said, and declined further comment.
A followup request for information from the U.S. Forces Japan public affairs office remained unanswered at press time.
In an August 15 article in the military newspaper the Stars and Stripes, Japanese and U.S. officials said that the dugong listing isn't expected to delay the planned construction.
The newspaper also quoted Ministry of the Environment spokesperson Harumi Nakajima as saying the listing is meant simply to inform the public that dugongs are at risk.
The agency does not plan to restrict activities at dugong feeding grounds as part of the new classification, she said.
Hideki Yoshikawa is a member of the Save the Dugong Campaign Center in Okinawa.
He said in an email that the Defense Facilities Administration Agency (DFAA), a Japanese organization that manages facilities for the U.S. military, does appear to be moving ahead with the base construction.
"We are concerned that the DFAA will do anything to carry out the plan, including ignoring of the listing of the Okinawa dugong on the [Ministry of the Environment's] Red List," he said. "Implications are there and scary."
The next hearing in the lawsuit is scheduled for September 17.
But even if the lawsuit is successful, stopping the base expansion is not enough to save the Okinawa dugong, the Center for Biological Diversity's Galvin said.
Fishers must take care to prevent dugong entanglement in their nets, and other landfill projects must also be halted, he said.
Dugongs and manatees are the last remaining sirenians, a group of marine mammals that scientists believe evolved from elephants about 60 million years ago.
An April 1997 DNA study published in the Journal of Molecular Evolution said that dugongs and manatees split into different species about 22 million years ago.
While dugongs are mostly native to Southeast Asia, manatees are found in waters around the southeastern U.S., Central and South America, and West Africa.
Today all sirenians are considered endangered.
Nicole Adimey is a wildlife biologist with the U.S. Fish and Wildlife Service in Jacksonville, Florida, who studies sirenians.
"Human activity is probably the most significant non-natural mortality factor for both dugongs and for manatees," Adimey said.
Manatees face more fatal boat traffic, especially in Florida, than dugongs.
Also, development in Florida has modified the normal distribution range of manatees in a way that experts fear is not sustainable.
In the last several decades, as their southern habitat has dwindled, manatees have become conditioned to using power plants as a source of warm water, which is necessary for their survival in the winter.
(Read "Manatees Seek Power Plants, Warm Springs as Safe Havens" [October 20, 2006].)
If these plants shut down, manatees may literally be left out in the cold.
While sirenians' exact ecological role is unclear, the public identifies with the massive mammals, Adimey said, and efforts to protect them have met with some success.
"It's just kind of our responsibility as caretakers of this world to ensure that the future of these animals is secure," she said.
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