Dugongs once floated peacefully in southern Chinese waters. Now, however, because of hunting, habitat loss, collisions with ships and other human interventions, these gentle marine mammals are “functionally extinct” in China, according to a paper published Wednesday in the journal Royal Society Open Science.
Weighing more than 800 pounds and measuring up to 10 feet long, dugongs (Dugong dugon) are massive mammals that spend most of their time grazing on underwater seagrass. Though they’re the only surviving species of the Dugongidae family, dugongs—often called “sea cows”— are cousins of manatees, another large, fleshy marine mammal. (The two animals look very similar but are differentiated by their noses and tails: Dugongs have broader, trunk-like snouts and fluke tails that resemble those of dolphins.)
Dugongs can live to be 70 years old, but they have a slow breeding rate, which makes it harder for them to bounce back from population disruptions. When they don’t have enough seagrass to eat, dugongs may delay breeding. And as seagrass increasingly disappears from the world’s oceans, dugong populations can fall into a downward spiral.
The International Union for Conservation of Nature (IUCN) lists dugongs as “vulnerable” on a global scale, and the Chinese government has classified them as “Grade 1 National Key Protected Animal,” the country’s highest level of protection, since 1988. But researchers noticed the status of dugongs in Chinese waters was “poorly understood,” they write in the paper, so they set out to learn more.
They interviewed hundreds of professional fishers living and working in four southern maritime provinces—Hainan, Guangxi, Guangdong and Fujian—which encompass the entire known range of dugong habitat off the coast of China. They also studied all available historical records, from the 20th century to the present.
Conversations with the experienced fishers painted a grim picture: Of the 788 study participants, who had been fishing for an average of 25 years, just 5 percent reported having ever seen a dugong.
Only three of the fishers had spotted the species within the last five years. Two of those sightings were in an area far away from where dugongs had historically been in China, which suggests that those animals were actually “vagrant individuals” from the Philippine dugong population, per the study.
Further, the researchers found no verified field observations recorded since 2000. Dugong numbers peaked around 1960 and, starting around 1975, their numbers appeared to rapidly decrease.
Dugongs, the researchers conclude, are the first large vertebrates to go extinct in Chinese waters.
"The dugong is a sad example of what is happening to the marine environment where there is increasing encroachment of human activities,” Kristina Gjerde, an IUCN policy adviser, tells the BBC’s Esme Stallard.
The animals still live in other parts of the world, including off the coasts of 37 countries from East Africa to the western Pacific, but their disappearance in China is a “sobering reminder that extinctions can occur before effective conservation actions are developed,” the researchers write.
Though China has made seagrass restoration a top priority, those efforts couldn’t save the dugong. But there’s still hope for other threatened marine animals, and the researchers urged countries along the South China Sea to take “immediate and extreme measures” to prevent further extinctions.
“The likely disappearance of the dugong in China is a devastating loss," says Samuel Turvey, a researcher at the Zoological Society of London's Institute of Zoology and one of the study's authors, in a statement. "Their absence will not only have a knock-on effect on ecosystem function, but also serves as a wake-up call."