The Yangtze Finless Porpoise was once considered a subspecies of the narrow-ridged porpoise together with the East Asian finless porpoise. It was recognized as an independent species in 2018, which increased the number of cetacean species from 89 to 90. This also marks the addition of another endemic species in China.
Yangtze River porpoises like to move alone or in pairs, and usually form a group of no more than 4-5, but there are also records of 87 together. Yangtze River porpoises can emit two types of sound signals: high-frequency pulse signals and low-frequency continuous signals. High-frequency pulse signals are composed of a series of single high-frequency narrow pulses, generally between 20 and 120, which are sonar signals or echolocation signals, mainly emitted when detecting the environment and hunting; low-frequency continuous signals are time-continuous signals. Due to the different frequencies, some sound like sheep or birds to human ears. It is basically not gregarious with the white-fin dolphin, but they occasionally play together. The Yangtze River dolphin has a wide range of adaptability to water temperature and can live normally from 4 to 20℃.
The Yangtze River dolphin is lively and often swims up and down in the water, rolling, jumping, nodding, spraying water, and turning suddenly. When swimming sideways, one leaf of the tail fin is exposed above the water, swaying left and right, and passing through the air. When frightened, they swim rapidly, then lift their bodies off the water once or several times in succession, with most of their bodies above the water surface, and only the tail blade gliding forward in the water. Occasionally, the entire body jumps out of the water, reaching a height of 0.5 meters. When swimming upright, two-thirds of the body is above the water surface, and it maintains a vertical posture with the water surface, which can last for several seconds. Whenever there is a large ship sailing in the river, the finless porpoise likes to follow it closely and ride the waves. It also has an interesting water-spitting behavior, exposing its head above the water surface, while swimming forward quickly, opening and closing its mouth, and spraying water from its mouth from time to time, sometimes spraying water 60-70 cm away. When breathing, only the head is exposed, the tail fin is hidden underwater, and then it dives underwater in a bouncing manner. The breathing interval is generally about 1 minute, but if it is frightened, the diving time can reach 8-9 minutes. Generally, if you don't bend your waist when entering the water, you won't stay underwater for a long time, but if you bend your waist a lot when diving, it means you will dive deep and will not come out of the water continuously. When swimming downstream, the next water exit is generally about 10 meters ahead of the previous water exit. When swimming against the current, it is generally about 5 meters ahead of the previous water exit. When swimming upstream, it can only move forward about 3 meters. If strong winds are about to occur, the breathing rate of the finless porpoise will increase, and it will be exposed to the water very high. The head will mostly face the direction of the wind to "go against the wind" to exit the water. Fishermen working on the Yangtze River call this behavior of it "worshiping the wind". This may be because the air pressure is low before the weather changes, so it has to increase its breathing rate to get enough oxygen.
The food of the Yangtze River finless porpoise includes fish such as blue-scaled fish, jade tendon fish, eel, perch, anchovy, big silver fish, shrimp, squid, etc., which changes with the environment. When foraging, it first swims quickly, mostly diving deep, frequently exposing the water, breathing loudly, and sometimes there is dirt on its mouth, stirring up waves tens of centimeters high on the water surface. After finding the prey, it will rush forward, then quickly turn around, use its tail blade to hit the water and stir the water, drive away the fish school, and scare them away. Then it will swim quickly, quickly approach the prey, and flexibly turn and swing its head to accurately locate it. After biting the prey, it will adjust the fish head to face the throat and swallow it quickly, and then proceed to the next prey. Sometimes it will hold several smaller fish in its mouth and swallow them again. After eating, it will swim slowly or float in the water. If a group finds a school of fish, they will coordinate their actions and swim separately from each other. They will not dive deep and swim in an uncertain direction, often accompanied by forward pounces and head shaking movements, surrounding the prey. The dozens to hundreds of silvery-white small fish being chased are forced to jump out of the water, making the water surface silvery and shining, and the scene is spectacular. While the finless porpoise is hunting, the gulls circling in the air will arrive in time, and take advantage of the small fish to surface and keep flying across the water to grab the small fish.
The mating of Yangtze River dolphins usually takes 30-60 minutes, starting from the passionate chase between male and female animals to the end of mating. It can occur more than ten times a day, and it can happen day and night. When chasing the female, the male animal swims back and forth with its abdomen and tail peduncle, with various postures such as rolling, sideways swimming, and back swimming. The water surface is often stirred up with waves and splashes. When swimming together, the male and female animals emerge from the water or dive into the water in parallel, touching and rubbing different parts of their bodies. Sometimes they touch each other with the tip of their kisses, kiss each other's reproductive parts, etc., gradually triggering mating. When the estrus reaches a certain degree, they face each other with their ventral surfaces, close their reproductive fissures, and the male animal exposes his genitals. They continue to swim together until the male animal's genitals are inserted into the female animal's vagina to achieve mating. At this time, the water surface is relatively calm, and about 2 minutes later, the mating is over. The male and female animals slowly float up from the water and then separate.
About 10 days before the birth of the Yangtze River porpoise, the female's breathing rate increases day by day, and her food intake decreases gradually. Five days before the birth, the breast and genital fissures gradually expand and open, and the nipples protrude. When swimming, they often stop at the water surface, and their bodies sway from side to side, as if they have lost their balance. About 25 hours before the birth, the vulva opens further, and milky white liquid flows out of the vaginal opening. During the birth, the vaginal opening forks, and the female swims up and down quickly and rolls every 3 minutes or so, and then swims slowly after about 2-3 minutes, and then swims quickly again after a 3-minute interval. Every time she swims quickly, the female begins to exert force so that the baby can be born a little, but when she relaxes, the baby porpoise shrinks back again. After a pause, the female suddenly exerted force continuously to deliver the fetus as a whole. The cub immediately swam upwards with all her strength, while the female swam with her belly facing up in the opposite direction of the cub, breaking the umbilical cord. The cub rushed out of the water and breathed air. The whole delivery process took about 160 minutes.
The Yangtze River porpoise gives birth in October, with one cub per litter. The female porpoise has obvious behaviors of protecting and helping the cub, which are manifested in carrying and carrying, which is very interesting. When carrying, the cub's head, neck and abdomen are all close to the female porpoise and lie on the back. When breathing, the cub and the female porpoise emerge from the water one after another. When the cub grows up, the female porpoise often uses flippers or tail leaves to support the cub's lower jaw or other parts of the body to swim, and they also emerge from the water one after another when breathing. The carrying method is more common. The female dolphin and the baby are very close, about 5-10 meters apart, but their bodies are not touching. They also emerge from the water one after another. During lactation, the female dolphin and the baby often appear in shallow and slow water areas. The female dolphin slightly tilts her body to one side, exposing one flipper, and the baby is close to the female's abdomen. Each lactation lasts about 5-10 minutes. Sometimes the male dolphin also participates in raising the baby, letting the baby swim between the male and female dolphins, but generally closer to the female dolphin. The "family" sinks and floats in the water at the same time, almost parallel to the surface of the water. The female finless porpoise has a strong maternal instinct. If the baby is unfortunately captured, the female dolphin often cannot bear to abandon it, so she is often captured at the same time.
After the extinction of the Baiji dolphin, the finless porpoise became the last remaining cetacean in the Yangtze River. The genetic data revealed a distinct genetic makeup for the Yangtze finless porpoise, and the researchers hope to spur long-term efforts to prevent the destruction of its habitat.
The threats facing the Yangtze finless porpoise are mainly from the impact of human activities. The noise and propellers of the high-density and busy shipping vessels in the Yangtze mainstream are the biggest threats to the finless porpoise. In addition to the impact of indiscriminate fishing and the large-scale use of illegal fishing gear in the Dongting Lake area, water pollution and the construction of some water conservancy facilities, the large-scale use of fixed nets in the lake area occupies a large amount of water surface during the dry season. Human activities such as the construction of water conservancy facilities and water pollution are still intensifying, making the Yangtze finless porpoise face the same threats as the white-fin dolphin, and the number in the wild has dropped sharply. The number is only about 1,200-1,500, which is less than that of giant pandas, and is declining at a rate of 5%-10% per year. In addition, the extinction rate of finless porpoises around Dongting Lake is the fastest in the entire Yangtze River Basin.
After China took protective measures for the white-fin dolphin, the finless porpoise and other aquatic animals, their numbers have rebounded. Dozens of them often appear on the surface of the Yangtze River, swimming upstream and playing in the surging water. Their black backs sometimes jump out of the water and sometimes dive into the water, rising and falling, turning flexibly, and the scene is quite spectacular. What is more gratifying is that passing ships have taken the initiative to give way to the Yangtze River finless porpoises, fearing that the finless porpoises will be frightened, showing that people's awareness of protecting wild animals is gradually increasing.
Listed in the "Red List of Endangered Species of the World Conservation Union" (IUCN) ver 3.1: 2017-Endangered (EN).
Listed in Appendix I, Appendix II and Appendix III of the 2019 edition of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Listed in the first level of the List of Nationally Protected Wildlife in China (February 5, 2021).
Listed in the China Biodiversity Red List - Vertebrate Volume (May 20, 2015) - Critically Endangered (CR).
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