You must be kidding! How can dolphins run to the Mekong River? Aren’t they in the sea?

In the southeast of China's Qinghai-Tibet Plateau, there is a famous north-south mountain range - the Hengduan Mountains. Some of the rivers flowing in the Hengduan Mountains will continue to move south, cross the border, and flow into the ocean in Southeast Asia.

The Lancang-Mekong River is such a transnational river. It originates in the Yushu Tibetan Autonomous Prefecture of Qinghai Province and has gained many names along the way: when it was in Qinghai Province, it was called "Zaqu", and it was only when it reached the Tibet Autonomous Region that it was named "Lancang River".

Lancang River flowing through the valley | Chen Zhao / wiki commons

The Lancang River continues to flow south with this name all the way to Xishuangbanna Dai Autonomous Prefecture in Yunnan Province. After crossing the border, it changes its name and becomes the Mekong River .

We continue south along the Mekong River, passing through Myanmar, Laos and Thailand, and the next stop is Cambodia . Here, we will hear a story: there are dolphins in the Mekong River, they are our deceased ancestors, always accompanying our boat.

There are indeed dolphins living in the Mekong River . They are the Irrawaddy dolphins (Orcaella brevirostris) of the Delphinidae family of the order Cetacean.

Irrawaddy dolphins come up to the surface to breathe in Kratie, Cambodia | Jean-Claude Durka / Wikimedia Commons

To survive, take an unconventional approach

Generally speaking, animals that live in salt water find it difficult to adapt to freshwater environments because the environmental differences are too great.

However, some animals that originally lived in saltwater have evolved the ability to travel to freshwater for business or tourism. For example, some fish can eat both saltwater and freshwater, and they are called euryhaline fish , such as the European eel (Anguilla anguilla) and the bottom killifish (Fundulus heteroclitus).

European eels at the Nancy Museum in France. Although they are good at both salty and fresh food, this does not prevent the European eel from becoming a critically endangered (CR) species | G. Garitan / Wikimedia Commons

But some aquatic animals that originally lived in saltwater are even more amazing. They have even evolved into independent populations living in freshwater. The freshwater populations spend their entire life cycle in freshwater , isolated from the marine populations.

Irrawaddy dolphins are such strong creatures. Wild Irrawaddy dolphins can be found in many coastal saltwater, freshwater and brackish waters in the tropical and subtropical Indo-Pacific region. They can be divided into marine populations and freshwater populations .

Irrawaddy dolphins in the Sundarbans off the coast of southern Bangladesh | Dibyendu Ash / Wikimedia Commons

Marine populations are distributed in patches from Borneo and the central islands of the Indonesian archipelago north to Palawan in the Philippines and west to the Bay of Bengal and the Gulf of Thailand. They prefer sheltered coastal waters with freshwater inflows , such as river deltas, mangrove channels, and estuaries.

Freshwater populations are distributed in three large rivers (the Irrawaddy in Myanmar, the Mahakam in Borneo, and the Mekong in Cambodia and Laos) and two partially isolated brackish lagoons (the Chichilika Lake in India and the Songkhla Lake in Thailand).

The distribution range of the Irrawaddy dolphin. The smaller one in the middle of the picture is its distribution in the Mekong River. | Xiao Man/Wikimedia Commons

Three parts scheming, seven parts cuteness

Unlike many other dolphins, the Irrawaddy's snout is very short, which makes its head look round; plus, its mouth has an upward arc, so from the front it looks like a round face with big eyes - if you are familiar with the Yangtze River dolphin, you will think they look a bit alike.

An Irrawaddy dolphin surfaces in Ko Pole, Cambodia | David Dove / WWF Greater Mekong

In addition to its cute face, another unique feature of the Irrawaddy dolphin is that it is one of the few cetacean species that can make the "nodding" gesture .

As humans, we can nod easily because we have flexible neck joints; however, the cervical vertebrae of most cetaceans are fused together, making it harder to nod than to make a leader nod. But where there are the majority, there are the minority - the Irrawaddy dolphin is one of the dexterous nodding ones whose cervical vertebrae are not completely fused together.

Skeleton specimens of the Irrawaddy dolphin in the Natural History Museum of the University of Pisa, showing their flexible cervical vertebrae | Notafly / Wikimedia Commons

In addition, another common behavior of cetaceans is spy hopping. Perhaps because they want to observe the situation on the sea surface, they raise their heads and pectoral fins and stick their heads out of the water , which is a bit like humans standing upright in the water. Then, they will gradually sink into the water. Killer whales, sperm whales and other species have this behavior.

Killer whales are probably the most famous snorkelers | Gregory "Slobirdr" Smith / flickr

Irrawaddy dolphins also float, but the most unique thing about them is that when they float, they often spit out a 1.5-meter-long water column from their mouths .

Scientists have found that this behavior of spitting water may be for finding food. When people use water guns to play water fights, if they are accidentally hit, it actually hurts a little. However, the Irrawaddy dolphin can spray water columns so far, and the effect is more than just "a little painful" - when the Irrawaddy dolphin is looking for food, it can use water columns to surround fish and even stun them .

Spit in your face｜Roland Seitre / naturepl.com

But is it cuteness that caused the trouble?

In the eyes of commercial aquariums that rely on animal performances as their main profit source, Irrawaddy dolphins have always been popular animals . Not only do they have a cute appearance and unique water-spitting behavior, but they can also live in freshwater tanks, eliminating the high operating costs of seawater tanks.

If there is a market, there will naturally be people who catch wild Irrawaddy dolphins for profit - after all, people can easily catch them with just a motorized canoe and a fishing net.

Wild populations in Thailand, Myanmar, Cambodia, Vietnam and Indonesia were captured in large numbers for export and aquarium display until an international commercial trade ban was implemented in 2004, which stopped the export trade of Irrawaddy dolphins.

Dolphin shows may seem exciting, but behind the scenes there are a series of problems, including abuse and lack of animal health assurance. Many responsible zoos and aquariums have shut down their animal show-related businesses | INSAR / Wikimedia Commons

The ban is timely. Although the global population of Irrawaddy dolphins is about 7,000, most of them are marine populations. The total number of freshwater populations of Irrawaddy dolphins in the three major rivers is less than 250, and the Irrawaddy dolphins in the Mekong River only live in a 118-mile river between Cambodia and Laos. It is estimated that there are only 92 left , and they can no longer withstand any more hunting.

Moreover, the welfare of Irrawaddy dolphins is difficult to ensure in commercial aquariums. Spitting water is a natural behavior for them in the wild, but in captivity, they will never do it without the trainer's command.

Still see hope for the future

It's not just fishing. Irrawaddy dolphins are accustomed to living in nearshore and freshwater waters, and these habitats are also areas with a lot of human activities. Therefore, compared with most other dolphins living in the open ocean, Irrawaddy dolphins are more likely to conflict with and be affected by human activities .

Drowning in gillnets is the main threat to wild Irrawaddy dolphins in their habitat. Although most fishermen sympathize with the plight of the dolphins, giving up their traditional livelihoods is a problem that fishermen cannot solve on their own, and more professional institutions and forces need to intervene.

Another identified threat to Irrawaddy dolphins is noise pollution , primarily from high-speed vessels and dynamite fishing.

Fishing boats moored on the Cambodian coast | Marcus61 / pixabay.com

In order to save the endangered wild Irrawaddy dolphins in the Mekong River, Cambodia's Fisheries Law lists Irrawaddy dolphins as endangered species and provides them with full protection.

Thanks to everyone's unremitting efforts, the death toll of Irrawaddy dolphins has gradually decreased, and people have even found 10 newborn dolphins on the coast of Cambodia.

The Irrawaddy dolphin has been severely harmed in the past because of its uniqueness, but as the public's environmental awareness increases, its uniqueness can arouse people's desire to learn more about this species . As Dr. Jane Goodall said, "Only when we understand can we care; only when we care can we take action; only when we take action can all life have hope."

Please let them live freely｜Dan Koehl / Wikimedia Commons

Author: Pei Ran