After the white sturgeon, will the “mermaid” also leave?

Sad! Recent studies have shown that dugongs are functionally extinct in Chinese waters. The last sighting in China was 14 years ago. Is the "mermaid" really going away?

Written by Liu Yadan (Researcher of the Chinese Society of Fisheries, National Chief Scientific Communication Expert)

Editor/Liu Zhao and Wu Xinlu

Recently, just one month after the bad news of the disappearance of the Yangtze River sturgeon came, another bad news came: the mermaids in our waters - dugongs are functionally extinct. Compared with the news of the extinction of the sturgeon, the latter makes us more sad, because the image of dugongs is more closely related to our culture and carries more beautiful hopes. Although most people have not seen mermaids with their own eyes, her beautiful image is not lacking in ancient documents, legends, fairy tales, or modern poems, stories, and film and television works, carrying the beautiful fantasy of many generations of childhood.

What kind of creature is a dugong?

Dugong (scientific name: Dugong dugon) belongs to the order Sirenia, class Mammalia. There are only four species of Sirenia in existence, which are divided into two families, namely: Sirenia and Dugong. Sirenia has three species, while Dugong has only one species. Because they are "brothers" in the same order, the appearance of dugongs is very similar to that of manatees, and their habits are also very similar, except that the skin color of manatees is darker.

▲Photo source/Enjoy Philippine

Sirenia is a very special group of marine mammals, and is the only herbivorous mammal in the ocean. It shares a common ancestor with the Asian elephant on land. This is very interesting, because scientists who study marine life have found that many mammals in the ocean have come from land to the ocean, and most of them are carnivorous animals, such as whales. They also infer that due to environmental changes, their prey on land has decreased, so they have to "go to the sea to eat fish." As for why the herbivorous manatees go to the sea, scientists have not yet given a clear answer, and we need to continue to explore.

Because they need to eat grass, most dugongs are found in seagrass patches about 20 meters from the coast. Sometimes when the tide rises, they will go with the waves into the estuary. After eating, they will return to the sea with the ebb tide and rarely swim to the open sea.

Dugongs like to live in warm marine environments. Low temperatures will damage their skin, so they usually live in waters with seawater temperatures above 20°C. Their distribution is closely related to water temperature, ocean currents, and the distribution of seaweed, which is their main food. They were originally widely distributed, from the east coast of Africa to the west Pacific, the waters of Guangdong and Taiwan in my country, and the southern part of New South Wales in Australia.

Why are dugongs called mermaids?

There is no scientific evidence to prove why people call dugongs "mermaids". However, from our Eastern mythology to Western fairy tales, there is a consensus on this, which is really rare. Perhaps it is because there were no modern telescopes on the sea in ancient times that the Song Dynasty man Cha Dao said in "Zu Yi Ji" that when he was sailing, he saw "a woman appeared on the sea, with red clothes and two exposed legs, and messy hair", and the image of the beautiful and brave mermaid in Denmark came into being.

▲Photo provided by Danish Mermaid Statue/Liu Yadan

Judging from the appearance of the dugong, the "mermaid" is not only not beautiful, but also silly and stupid. Its body is like a giant spindle, with a large body and a small head, a crescent-shaped tail, eyes like mice, nostrils inserted on the top of the head, ears that are too small without ear rims, and two fangs exposed at the lips... It can be said that it looks very ugly!

What is the beauty of dugongs? First, there is a pair of plump breasts next to the pectoral fins of dugongs, which are located in a position very similar to that of humans; second, the dugong is light cream in color, which is similar to the color of human skin; third, there is sparse long hair on its back, which is a bit like human hair.

In addition, dugongs have similar living habits to humans. For example, dugong babies grow up by sucking their mother's milk. The mother dugong floats on the water sideways to feed her baby, which is also similar to humans. There are even legends that dugongs use their flippers to hold their babies upright in the water to feed them, with their upper bodies exposed above the water, which is very similar to human mothers breastfeeding, but there is no definite scientific evidence for this.

Dugongs are gentle, slow-moving, timid and shy, a bit like traditional women in ancient times. From a human perspective, they are quite "human".

▲Dugong is one of the few herbivorous mammals in the ocean. Image source/Pinterest

Why did the dugong disappear?

In recent years, biodiversity has been a focus of international and domestic attention. While translating and studying many books and articles at home and abroad, the author found that almost all experts pointed out that many of our behaviors are increasingly having a negative impact on biodiversity. Scientists have evaluated more than 47,000 species and found that 36% of them are threatened with extinction.

At present, dugongs in my country have been officially declared functionally extinct. What does functional extinction mean? Simply put, there are too few dugongs in the wild, and they may not even be able to find companions, let alone fall in love, have children, and expand their population. If we seriously think about the specific reasons, I think the following points are the main ones.

Hunted because of treasure

Dugongs are one of the oldest marine animals in the world. Their entire bodies are treasures. Four thousand years ago, humans began to hunt dugongs for their meat, oil, bones, carvings, and leather... Currently, only a few isolated and nearly extinct populations of dugongs remain, and most of the existing dugongs live along the northern coast of Australia. In addition, although they are not the target of fishing in fishery production, the occasional accident of being trapped in fishing nets and drowning also threatens their survival.

Living environment deteriorates

Dugongs mainly live in tropical shallow seas. In my country, they are mainly distributed in Guangdong, Guangxi, Hainan and the southern coast of Taiwan. Dugongs are not picky eaters and can eat almost any aquatic plant, such as seaweed, water grass and other juicy aquatic plants, as well as fiber-containing rushes and grasses. However, they have a particularly large appetite and can eat more than 45 kilograms of aquatic plants every day, so most of their time is spent on eating.

With the rapid development of coastal economic construction, pollution of buildings, waterways and waters has seriously damaged their habitats. In particular, these human activities have caused their main food, seaweed and algae, to be either polluted or desertified, making it impossible to find edible food.

Threats increase due to climate change

It is an indisputable fact that climate change has led to changes in the biological and food chains in the ocean. Climate change has led to a reduction in food in the ocean. The docile dugongs have poor eyesight, are fat, slow in movement, and have poor swimming skills. They often become prey to predators, especially some large carnivorous aquatic creatures, such as sharks, which are also natural enemies of dugongs' survival and reproduction. Small dugongs are fragile and have very thin skin, so they often become a delicacy in the mouths of sharks.

Although dugongs reproduce most of the year, they have a long life cycle, with an average lifespan of 78 years. Therefore, every stage of their life is relatively long: the gestation period takes 11 to 14 months, and they only conceive once every three years, with only one calf born each time. It takes about 7 to 8 years from birth to maturity. Each little dugong is hard-earned, and it is a pity to see it fall into the mouth of a shark!

Are we taking any conservation measures for dugongs?

The protection of dugongs is a global issue. All countries are working hard to save them. Regional cooperation between countries where dugongs are active has been carried out and strengthened to ensure the survival of this unique species. Data from fisher surveys conducted in 20 countries, including Pacific island countries, South Asia and the United Arab Emirates, have been released. Based on these data, all parties assess the impact of fisheries on dugongs' migratory routes on their survival. They are integrated into a geographic information system to identify problem areas, provide key information on existing populations and maps of areas such as seagrass beds. Related surveys have also been expanded to areas such as East Africa and the West Indian Ocean Islands, the Northeast Indian Ocean and South Asia. Countries have also adopted other methods to protect dugong habitats, breeding areas and foraging areas, such as establishing marine protected areas and taking temporary fishing bans.

As early as April 1986, the Chinese government approved the establishment of the Guangxi Hepu Yingpan Port-Yingluo Port Dugong Nature Reserve to protect dugongs; in October 1992, the State Council approved the upgrade of this reserve to a national nature reserve. The reserve is located in Hepu County, Beihai City, Guangxi, with a coastline of 19.6 kilometers and an area of ​​about 350 square kilometers. The protected species include not only dugongs, but also rare and endangered species such as Chinese white dolphins and finless porpoises.

In recent years, my country has promoted the construction of marine ranches, the first of which is to restore seagrass beds and seaweed beds. Seagrass beds, mangrove ecosystems and their marine ecological environment are the main habitats of dugongs.

In terms of protection level, the dugong was listed as a national first-class protected animal in the "National List of Key Protected Wild Animals" in 1988, and was included in this list again in February 2021.

Biodiversity conservation is a long-term, complex, comprehensive and huge project. Although we have been actively taking various measures to protect it, in recent years, dugongs, white sturgeons, baiji dolphins, and giant softshell turtles have been declared functionally extinct. This shows that ecological protection and biodiversity conservation are facing unprecedented challenges. The speed of species extinction is unimaginable, and our attention and measures often cannot keep up.

However, some successful examples around the world show that many measures people have taken to protect biodiversity have shown results. Researchers believe that although dugongs are functionally extinct in Chinese waters, there are still other individuals distributed in the waters of Australia and East Africa. The legend of "mermaids" will come back, giving us more beautiful fantasies about the world!

However, if we want to avoid further loss of biodiversity, we need to take more action. We should not only save species from the brink of extinction through the careful application of conservation strategies, but also pay attention to other threatened species, make full use of various scientific conservation measures, and actively take conservation actions. We believe that the process of biodiversity loss can be slowed down or even successfully stopped, even if it cannot be reversed.

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