A large group of finless porpoises appeared in the Yangtze River! This group of "smiling angels" is the "barometer" of the Yangtze River's ecology

Recently, Anhui Province discovered a large group of finless porpoises during simultaneous monitoring of finless porpoises. Why is the change in the number of Yangtze finless porpoises so important? Are finless porpoises "pigs" in the water? Let's find out >>>

Compiled by New Media Editor Duan Dawei

On the afternoon of March 10, the Yangtze River Dolphin Protection Association in the suburbs of Tongling City, Anhui Province, discovered a large group of Yangtze River dolphins during simultaneous monitoring of Yangtze River dolphins. When the operating boat reached the Xuba River section in Tongling City, more than 30 wild Yangtze River dolphins jumped out of the water, some swimming slowly and playing leisurely, while others jumped out of the water and chased the waves. Among them, mother and child dolphins could be seen, presenting a beautiful scene of harmonious coexistence of natural ecology.

Pigs know if the Yangtze River is healthy

Why is the change in the number of Yangtze finless porpoises so important? Wang Ding, a researcher at the Institute of Hydrobiology, Chinese Academy of Sciences and chairman of the Wuhan Baiji Dolphin Conservation Foundation, said that the Yangtze finless porpoise is a national first-class protected wild animal and a freshwater cetacean unique to the Yangtze River. It is known as the "giant panda in the water" and has high requirements for the water environment. The Yangtze finless porpoise is at the top of the food chain of aquatic animals in the Yangtze River. The survival status of the finless porpoise is a "display" of the ecological environment quality of the Yangtze River. It can be said that the number of finless porpoises has the final say on the water environment of the Yangtze River.

In the past 40 years, the number of Yangtze finless porpoises has dropped sharply. In the early 1990s, there were about 3,600 finless porpoises in the Yangtze River. In 2006, the number dropped sharply to about 1,800. By 2012, there were only about 1,045 left. The statistical data of the three Yangtze River expeditions showed a sharp decline, which aroused the concern of all sectors of society. Many scientists, including Wang Ding, are worried that the finless porpoise will follow the footsteps of the Baiji dolphin.

▲Qiqi, the only baiji dolphin successfully raised by humans (Photo source: Beijing News)

In 2007, the baiji was declared "functionally extinct" in the wild. In 2018, the World Conservation Union updated its Red List of Endangered Species, listing the Yangtze River baiji as "critically endangered." The Yangtze River baiji is known as the "Yangtze River Goddess" and the Yangtze River dolphin is known as the "Smiling Angel." Both live in the Yangtze River Basin and are endemic to China.

The petite "smiling angel"

Speaking of cetaceans, most people probably think of dolphins first. It is no exaggeration to say that the name of dolphins has already spread to thousands of households, and children are even more familiar with the stories about dolphins' wisdom and various behaviors.

From a taxonomic point of view, finless porpoises and dolphins are relatives. They are both from the order Cetacea, but the "finless porpoise" belongs to the genus Porpoise of the family Porpoise, while "dolphin" is a general term for animals in the family Delphinidae. They are two completely different species. Although the name of the finless porpoise contains the word "Jiang", most of its members actually live in the sea. There is only one type of finless porpoise that lives in fresh water, the Yangtze River finless porpoise.

The Yangtze River dolphin is a species endemic to China and the only remaining cetacean in the Yangtze River after the functional extinction of the Yangtze River goddess, the Baiji dolphin. Like the Baiji dolphin, the Yangtze River dolphin faces the same population threats. The World Conservation Union (IUCN) has listed the Yangtze River dolphin as "critically endangered" in 2013. In my country, the Yangtze River dolphin has been listed as a national first-class protected wild animal.

The Yangtze River dolphin has a blunt and round head, with the corners of its mouth raised 45 degrees, as if smiling, and is known as the "Smiling Elf of the Yangtze River" and "Smiling Angel". In addition, the Yangtze River dolphin has no movable lips around its mouth, so its smile will accompany it throughout its life. The Yangtze River dolphin has two rows of short, shovel-shaped teeth in its mouth, which are not used for chewing, but can firmly hold prey.

Unlike the huge whales in the ocean, the Yangtze River dolphin, which is adapted to river life, is very petite. The average length of an adult Yangtze River dolphin is about 1.2-1.6 meters, weighs about 50-70 kilograms, and lives about 20 years. Its head is short and nearly round, with a forehead that protrudes slightly forward, a short and wide snout, and upper and lower jaws that are almost the same length. The teeth are short and flat on the left and right sides and are shovel-shaped. The first five cervical vertebrae are fused, and there are usually 14 pairs of ribs. The middle part of the body is the thickest, and the cross section is nearly round.

In terms of proportion, the flippers of the Yangtze River dolphin are quite large. There is no dorsal fin on the back of the Yangtze River dolphin. The flippers are relatively large, triangular, pointed at the end, and have 5 fingers. The tail fin is relatively large, divided into two horizontal lobes. There is a 3-4 cm wide skin ridge on the back where the dorsal fin should be, and there are many keratin scales. The whole body is blue-gray or tile-gray, the abdomen is light and bright, the lips and throat are yellow-gray, and there are some irregular gray spots on the abdomen. The color of some individuals becomes lighter between the base of the two flippers on the ventral side and the anus, and some are even light red, which is particularly obvious during the breeding season.

The eyes of Yangtze finless porpoises are not big, with a diameter of about 2 cm. If you look closely, you will find a small hole shaped like a sesame seed 5-8 cm behind the eyes, which is the external ear hole of the Yangtze finless porpoise. The external breathing hole (i.e. nostril) at the top of the head is a half-moon-shaped crack when closed, about 3.5 cm long, with a movable valve inside to prevent water from entering the nasal cavity, which opens when out of water to breathe.

Is the Yangtze River Porpoise a "Pig" in the Water?

Although the Yangtze finless porpoise is an animal that lives in water and looks more like a fish after millions of years of evolution, it is ultimately a mammal. The average length of a Yangtze finless porpoise is 1.4 meters and its average weight is 60 kilograms. It has a relatively round body and a very round head. Its body is hairless and smooth.

When the ancients described an animal, they would usually use known animals for analogy. Among the known animals, the ancients were undoubtedly most familiar with poultry and livestock. Among the many poultry and livestock, it seems that only the pig can meet the requirements of a round body, a round head, and less hair on the body. Therefore, the term "Jiang pig" came into being. Of course, this is only one of the reasons.

As the most common mammal in the Yangtze River Basin, the Yangtze River dolphin was also caught by ancient people when they were engaged in fishing, and people also slaughtered and ate the Yangtze River dolphin. As early as the Song Dynasty, there was such a description in the "Zhenglei Bencao":

A sea fish, salty and non-toxic, eaten as jerky, it is like buffalo meat, with a slightly fishy taste...It lives in the sea, waiting for the wind and tide to emerge, shaped like a 㹠, with a sound coming from its nose and a hole on its head, from which it sprays water straight up, and lives in groups of hundreds. People first get its young and tie them in the water, then the mother will come and they can take her.

From the records we can see that the ancients regarded the Yangtze River dolphin as a kind of fish similar to pigs.

However, in the Qing Dynasty's "Haicuo Tu" there are records about the ancients slaughtering Yangtze River dolphins: there are two pieces of fat in the belly, which looks exactly like pig fat, and its liver, intestines, heart, lungs, waist and belly are all the contents of the pig's belly.

▲Evolutionary tree of Artiodactyls (Source: Internet)

This means that after the ancients cut open the Yangtze River dolphin, they found that its internal organs were very similar to those of a pig. In addition, its appearance was somewhat similar to that of a pig, so the ancients believed that it was a kind of pig that lived in rivers and seas, which is also one of the origins of its name. Of course, if you want to illegally hunt, kill, purchase, transport, or sell them now, you will be severely punished by law.

(Reference sources: Anhui Channel of People's Daily Online, Jimu News, Nanjing Yangtze River Porpoise Aquatic Life Protection, Science Curiosity, etc.)

Produced by: Science Central Kitchen

Produced by: Beijing Science and Technology News | Beijing Science and Technology Media

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