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Lipotes is a member of the genus Lipotes of the Cetacean freshwater family
[28]
Of the mammals.
[29
]
The adult Yangtze dolphin is a small whale. The body is fusiform; The snout is long and narrow, and the fumarole is long, located on the left side of the head; The eyes are small and above the back of the mouth; The ear holes are needle-shaped; Single nostril, on the left side of the head; The dorsal fin is triangular, the flipper limb is broad, the end is blunt; The caudal fin is sunken and crescent-shaped. The snout is long and narrow, the back of the body is pale blue-gray, and the belly is white.
[30
]
Females are larger than males.
[34
]
The Yangtze River dolphin gets its name because its belly is pure white.
[31
]
The Yangtze River dolphin is distributed in the middle and lower reaches of the Yangtze River, Dongting Lake, Poyang Lake and Qiantang River estuary.
[29
]
Yangtze River dolphin is hardy and likes to live in the deep water of rivers. It rarely comes near the shore and boats. It often swims to shallow waters to catch fish and shrimp to satisfy its hunger.
[32
]
Like to live in groups, mild temperament, often three or five in winter, sometimes as many as ten, wandering for food, food mainly fish, and eat aquatic insects and plants.
[33
]
The Yangtze River dolphin breeds from March to August every year and gives birth to one calf per litter. The newborn calf weighs about 5 kg.
[35
]
Life expectancy is generally 30 years.
[32
]
The Yangtze River dolphin was listed as critically Endangered (CR) on the IUCN Red List of Threatened Species in 2017.
[36]
It has been presumed to be functionally extinct and is a priority protected animal in China.
[29
]
Lipotes is a precious living fossil for studying the evolution of cetaceans, which is of great scientific value in bionics, physiology, zoology and military science.
[32
]
The Yangtze River dolphin is a rare aquatic mammal unique to China and is known as "the giant panda of the Yangtze River" and "living fossil".
[37
]
- Chinese name
- Yangtze river dolphin
- Latin name
- Lipotes vexillifer
- alias
- extinct , 鱁 zhu (ancient name) , White-flag dolphin , Yangtze River , Chinese river dolphin , Chinese finless porpoise , White bannerfish
- Foreign name
-
Baiji, Yangtze River Dolphin
(English)
Baiji [1] (in French) - world
- animalia
- The door
- Chordate phylum
- The outline
- mammalia
- Orders,
- cetacea [27-28]
- Families,
- Lipotes family [3]
- Belong to
- Lipotes L
- Kind of
- Yangtze river dolphin
- subphyla
- Vertebrate subphyla
- suborder
- Odontocetacea
- subclass
- Eutheria
- subspecies
- Monotypic species without subspecies [9]
- Namers and years
- Zhou, Qian and Li, 1978
- Protection level
- Critical Risk (CR) IUCN Standard [10]
Yangtze dolphins are differentiated from dolphin clades (
Delphinida
), the clade contains divide
Sperm whale
Classes outside all modern
Toothed whale
. Fossil evidence suggests that primitive dolphins were born 25 million years ago, and that they evolved from
Pacific
Enter the Yangtze River.
[11]
Chinese geologists in Guangxi in September 1981
Guiping
A fossilized jawbone fragment of a prehistoric animal was found, which came from an ancient Yangtze River dolphin called "Protoyangtze River Dolphin" (genus name:
Parapontoporia
). The fossil record of the ancient character of the original Yangtze River dolphin more than 20 million years ago, compared with the modern Yangtze River dolphin little difference. Perhaps the habitat space is relatively closed, survival competition and environmental changes are less, the Yangtze River dolphin retains the original form of its ancestors, so it is called "Yangtze River Dolphin".
Living fossil
".
[11]
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show
raw
t.
left
new
raw
generation
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The middle and advanced stage
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Eocene epoch
(56-34 million years ago)
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34 million years ago, toothed cetaceans diverged.
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Oligocene
(about 34-23 million years ago)
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25 million years ago, the dolphin lineage diverged, and at this time dolphins were the common ancestor of all modern toothed whales except sperm whales.
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Miocene Epoch
(about 23-5.3 million years ago)
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The Yangtze River dolphin appeared 20 million years ago. Some dolphins enter China's inland waterways from the Pacific Ocean.
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The Yangtze River dolphin appeared 5.3 million years ago.
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Pliocene epoch
(about 5.3-2.6 million years ago)
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All three species of Yangtze River dolphin that have been discovered so far have become extinct. The Yangtze River dolphin has become the only remaining species in its lineage (Lipoidea).
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The Yangtze River dolphin population has been stable and prosperous until the end of the 20th century due to the influence of human activities.
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Pleistocene
(about 260-117,000 years ago)
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holocene
(about 117,000 years ago to the present)
|
[11]
Lipotes are very ancient animals, according to
fossil
Research results, at least 40 million years in the Miocene and Pliocene have existed, older than the giant panda, is a real "living fossil." Like other cetaceans, it was originally a land animal, and due to environmental changes, it has returned to the water.
[17]
According to paleontologists' fossil research, the Yangtze River dolphin has appeared in China since the Miocene and Pliocene of the Tertiary period. In September 1981, Chinese geologists discovered a jawbone fragment in Guiping, Guangxi Province. The jawbone belongs to an ancient Yangtze River dolphin known as Proto-Yangtze River Dolphin.
Parapontoporia
It is also known as the Pacific Amphibious whale. The fossils record the ancient character of the original Yangtze River dolphin more than 20 million years ago, which has not changed much compared with the present Yangtze River dolphin. The Yangtze River dolphin still retains many skeletal positions of the original Yangtze River dolphin. The slow evolution of Yangtze River dolphins may be due to the competition for survival in the past or the lack of environmental changes, so they retain the ancient shape of their ancestors, which is why they are called "living fossil" and "giant panda in water".
[18]
There has been some controversy on the scientific classification of Yangtze River dolphins, mainly because of the disagreement on which family the Yangtze River dolphins belong to. For example, the IUCN Red List of Threatened Species lists it in the family Leptoliferidae (Yangtze River Family).
Lipotidae
ITIS once categorized it as
Subpufferidae
(
Iniidae
).
[12]
In 1918, Garrett S.Miller, president of the Smithsonian Institution in the United States, compared the bones of the Yangtze River dolphin and the subriver dolphin, and believed that the two were close relatives and included the Yangtze River dolphin in the subriver family. Most biologists supported his conclusion. In 1979, Chinese biologist Zhou Kaiya et al. rejected Miller's conclusion after comparing the skeletons of Lipotes and other freshwater dolphins, and established the Lipotes family, which has been recognized by some other scholars. Barnes, however, compared the fossils of the Fosseidae with the Lipotes and concluded that the lipotes should belong to the subfamily Fosseidae
Lipotinae
. After comparative anatomy study, Heyning placed the Yangtze River dolphin as a genus of subpufferidae. while
DNA sequence
The test results of the Yangtze River Dolphin showed that the subriver dolphin, the Fusi dolphin and the Baijiang dolphin belong to different families. So far, it is concluded that Lipotidae is an independent family.
[13]
The knowledge and description of Yangtze River dolphin in China has a history of over two thousand years. The ancient name of Yangtze River dolphin (sound ji), also known as white river, was first recorded in the dictionary of the Qin and Han Dynasties.
Erya
At that time it was called "Yangtze". It is said that at that time, there were more than 5,000 animals and they were widely distributed in the Yangtze River basin. The Yangtze River, which is about 1,700 kilometers long, is home to lipotes. Ancient human beings once mistakenly classified Yangtze River dolphins as fish. In the Jin Dynasty, Guo Pu (276-324 AD), who wrote commentary on Erya, gave a detailed description of the morphology and habit of Yangtze River Dolphin in Erya Zhushu, and correctly separated the Yangtze River dolphin into fish for the first time: Yangtze River, 䱜, has a body like a sturgeon and a tail like a fish. Beak small, sharp and long, teeth, top and bottom of the same bit, nose on the forehead, can be silent, little meat and much paste, viviparous, eat fine fish, large long. There are many in the river." . The Northern Song Dynasty (960-907)
Kong Wuzhong
Author of
Finless dolphin poem
". The "white horse" in the poem is the white Yangtze dolphin, and points out its relationship with
Finless dolphin
Not the same species: "Black finless porpoise, white white wirth." Shape different name special, with the house big water, deep fish, plunder to fat already. ..."
[3]
[5-6]
Tang Dynasty
Collection of Chen artifacts
's
Collect the relics of materia medica
"And the Ming Dynasty outstanding medical pharmacist
Li Shizhen
His book
Compendium of Materia Medica
The Yangtze River Dolphin (published in 1578) has been used as a synonym for the Yangtze River dolphin. Hao Wuxing (1755-1823) in the Qing Dynasty
Erya Yishu
Their mistakes are pointed out in "Chen Zangzi and Li Shizhen also take Yangtze River dolphin, but the name of Yangtze River dolphin is fat, that is, the fish, see Guangya, Yangtze River tail is similar, but the body is different." Kuoyuncera is a genus, similar in body to Na, not finless porpoise. In 1890, Fang Xu of the Qing Dynasty said in Worm Hui: "Dolphins, a Yangtze,... The big belly screams. The teeth are in the same shape." Another said: "There are times in the river today, the big one is long Zhangyu, the meat is edible, and the taste is like buffalo meat." Fang Xu's shortcoming is that he does not distinguish the Yangtze from other dolphins, but he is sure that some dolphins in the Yangtze River are actually Baiji.
[7]
To sum up, the Yangtze River dolphin has been described in ancient Chinese literature for many times in the past two thousand years. The Yangtze River dolphin was first discovered by the working people in ancient China. The name of Baiji has been handed down from generation to generation among the working people and is still used by many fishermen in modern times. According to the survey, the fishermen in the middle and lower reaches of the Yangtze River (including Anhui and Jiangsu) are all referred to as Baijiang, except Qingjiang in Anhui and Jiangma in Jiangsu. The local name Baiji refers to its lighter body color compared to the finless porpoise, rather than the misconception that it is white all over.
[7]
In 1914, Charles M. Macaulay Hoy, an American field naturalist, collected a specimen of the Yangtze River dolphin in the Dongting Lake area of China and brought it back to the United States
The Smithsonian Institution
(
Smithsonian Institute
President and scholar Garrett S.Miller has studied its morphology, anatomy, and the position of its bones and teeth. In 1918, in his paper "A New Species of Freshwater Dolphin from China", Miller identified the Yangtze River dolphin as a unique new species and gave it its Latin scientific name "Yangtze River Dolphin".
Lipotes vexillifer
And the English name "Chinese river dolphin" (literally translated as "Chinese finless dolphin"). Yangtze River dolphin has officially become a new species recognized internationally.
[4]
The original English name "Chinese river dolphin" has been popular in various publications for nearly a century, and was adopted by the British "Chinese River Dolphin".
Nature
The magazine quoted it and it became even more popular. However, in recent years, Chinese traditional culture has become increasingly influential in the international community, and western academic circles have begun to attach importance to Chinese literature research results, and take the earliest literature records as the priority principle of naming, so the official English name of the Yangtze River is changed to "Baiji".
[8]
American naturalist Charles Macaulay Hoy mistakenly referred to Baiji as the "White flag" and proposed that the name "White flag Dolphin" spread to the West, where Westerners began to refer to it as the "white flag", which is wrong. In 1955, the compilation and Translation Bureau of the Chinese Academy of Sciences compiled the "ridge propulsion name" called it the Baiji dolphin, in fact, its dorsal fin, tail fin and the back of the fins are bluish gray or gray, using the name of the Baiji dolphin is easy to misunderstand its fin color. In view of the fact that the name "white fin" is not historically applied, and does not fit the characteristics of the species, in March 1977, a famous Chinese zoologist
Zhou Kaiya
An article in the journal Acta Zoologica proposed that the Chinese name of the so-called "Baiji dolphin" has been changed to "Baiji dolphin" according to historical records and the common calling habits of the masses. After that,
Institute of Zoology, Chinese Academy of Sciences
The standard Chinese name for the species is officially "Baiji". While...
Convention on International Trade in Endangered Species of Wild Fauna and Flora
The 2019 edition of CITES and the February 5, 2021 edition of China's National List of Wildlife under Key Protection stipulate that the standard Chinese name of the species is "Baiji".
[7]
[14, 15]
Up to the end of 2010, a total of 89 lipotes specimens have been preserved in the world, of which 72 have sex records, of which 34 are male and 38 are female. There are 86 specimens in China, including 39 taxidermy specimens and 20 skeletal specimens (10 complete skeletal specimens, 1 incomplete skeletal specimen and 9 skull specimens). There are also seven immersed specimens, four of which are fetuses (two are stored at the Institute of Hydrology, Chinese Academy of Sciences, and the other two belong to the Museum of Natural Science and the Museum of Natural Science of Sichuan University, respectively)
Yueyang City agriculture Bureau
Aquatic Products Group), 3 pieces are adult (stored in the Institute of Hydrology, Chinese Academy of Sciences, Freshwater Fisheries Research Institute of Jiangsu Province, and
College of Life Sciences, Anhui Normal University
).
[4]
There are 3 bone specimens collected from Dongting Lake in the world, respectively
National Museum of Natural History
,
New York Museum of Natural History
and
The Natural History Museum
. The skull in the National Museum of Natural History of the United States is the type specimen collected by Hoy at Chenglingji in 1914 and sent to Miller for study. It is the first Lipotes specimen in the world. The specimen from the New York Museum of Natural History is the world's first complete skeleton of the Yangtze River dolphin, a female, which was purchased from fishermen in Yueyang for $21 when the museum staff formed a "Central Asian paleontological expedition" to China in 1921. The Natural History Museum in the United Kingdom has specimens dating from 1922
University of Aberdeen, UK
Found by chance while working in China by Professor Skinner of medicine, the female, the whole carcass was returned to London, allowing British academics to conduct the first anatomical study of the Yangtze River dolphin and specimen the skeleton.
[4]
Of all the surviving specimens, four skeleton specimens are "antiques" from the first half of the 20th century, namely three from the World and one skull from the Natural History Branch of the Shanghai Science and Technology Museum (collected in an unknown location around 1920 and filled with taxidermy specimens). Of the specimens collected after 1949, 10 were collected from the 1950s, 11 from the 1960s, 20 from the 1970s, 28 from the 1980s, and 15 from the 1990s. Only one specimen has been collected in the 21st century, namely "Qi Qi", which was raised in captivity until natural death in 2002, is the last specimen of Yangtze River dolphin. Many precious specimens have not been effectively protected, and the problems of specimen damage, decay, loss, unknown information, and information confusion are very serious, which need to be paid attention to and managed by relevant parties.
[4]
[16]
Male Lipotes vexillifer skull Collection [16]
The maximum length of female adult body is 253 cm and that of male adult body is 229 cm, indicating obvious dimorphism in body size. The Yangtze River dolphin has a medium and strong body with a long and narrow beak slightly upturned, a round frontal bulge, and a low triangular dorsal fin located about 2/3 body back from the rostral end, which is the most significant feature of its field recognition. The rostral process of the skull is narrow and narrow between the posterior end of the upper dentition and the preorbital fossa. There are obvious lateral furrows on the side of the rostral process, and there are shallow furrows equal in length to the upper dentition between the two maxilla on the ventral surface. The base of the maxilla extends posteriorly and meets the superior occipital bone at the posterior margin of the skull. The lateral margin turns upward to form the maxillary ridge, which curves strongly at the orbital part. The zygomatic process of squamosal bone does not reach the supraorbital process of frontal bone; The superior occipital bone is only slightly raised to the rear, so the posterior margin of the skull is straight; The two maxilla palatine parts meet; Pterygoid uncinate process with deep cavity; The earbone around the drum is in direct contact with the skull. The mandibular union is extremely long, its length approaching or reaching half the length of the mandible.
[2]
[17]
Its tail fins are flatly divided into two forks, the pectoral fins on either side are flat palm shaped, and the dorsal fins are triangular in shape. These four fins give the baiji excellent control of direction and balance while swimming in the water. Combined with smooth, elastic skin and streamlined body, the baiji can swim at speeds of up to 60 kilometers per hour while avoiding danger. It normally swims at a speed of 10 to 15 kilometers per hour.
[17]
The fins are broad and blunt at the tip. The eyes are smaller than those of Marine dolphins, but not as small as those of the Ganga dolphin. The upper part of the body is mainly blue-gray or gray, and the lower part is white. On the side of the head and neck there is a wavy division between gray and white from the eyes to the flippers. The white part extends upward into the gray part in front of the fin limb to form two prominent white spots. The female genital pore is located 18-20 cm in front of the anus.
[17]
The mouth has about 130 sharp teeth, which are homologous. The teeth are slightly flat back and forth, curved inward, and the crown has a net glaze fold formed by longitudinal ridges. The upper and lower teeth have 31-36 conical teeth per tooth row.
[17]
The skin is smooth and delicate, and has a special elasticity, the principle of the same elastic nylon fabric used in competitive swimming clothing, can reduce the turbulence generated around the body when swimming quickly in the water. The body color of newborn lipotes is slightly dark, the back of adult lipotes is usually light bluish gray, and the abdomen is white. The upper and lower sides of the horizontally extended fins and tail fins are the same color as the back and abdomen, respectively, so that the color distribution is exactly in line with the ambient color. When looking down from the water, the bluish gray of the back blends with the river water. When viewed from below the water surface, the white belly is similar in color to the strong light reflected from the water surface. This body color, which makes it difficult for other animals to recognize, is called countershading protection color, which allows lipotes to approach enemy or prey without being detected.
[17]
The Yangtze's brain weighs about 0.5% of its total weight, which is close to that of great apes. It is even thought that the IQ of Lipotes is higher than that of great apes. The mammalian brain needs to go into a dormant state after a period of use in order to function properly after awakening. Cetaceans have a unique brain system that allows one half of the brain to rest while the other half works. The brain of an adult Yangtze River dolphin is half asleep for seven to eight hours a day (similar to adult sleeping habits), and the whole brain is awake the rest of the time.
[17]
As mammals, Lipotes, like humans, need constant oxygen to their blood. When resting, land mammals can breathe involuntarily under the control of the cerebellum, while all breathing in cetaceans is autonomic breathing requiring brain response, so breathing must be carried out in a conscious state. When they lose consciousness due to illness or injury, they will sink to the bottom and enter a state of brain death when the remaining oxygen in the blood is used up. Therefore, drowning in water is a normal way of death for the elderly and weak Baiji river dolphins.
[17]
Chromosome set 2n=44, 14 autosomes are mesocentric chromosomes, 16 are submesocentric chromosomes, 4 are subtelocentric chromosomes, and 8 are telocentric chromosomes. In the sex chromosome, X is the medium centromere chromosome and Y is the telocentric chromosome.
[17]
|
Yangtze river dolphin
|
|
|---|---|
|
Lipotes have a medium and stout body with a long, narrow and slightly upturned beak and a rounded forehead. The maximum length of female adult body is 253 cm and that of male adult body is 229 cm, indicating obvious dimorphism in body size.
|
The slender body of the Chinese white dolphin is spindle-shaped, and the beak is protruding and narrow. The newborn white dolphin is about 1 meter long, the sexually mature individual is 2.0~2.5 meters long, the longest is 2.7 meters, and the weight is 200~250 kg.
|
|
They inhabit the lower reaches of the Yangtze and Qiantang rivers in China, as well as Poyang and Dongting Lakes, preferring to stay near the large vortices that form next to sandbanks.
|
The main habitats are mangrove waterways, bays, tropical river deltas or coastal brackish waters.
|
|
Chinese white dolphin
|
Baiji is found in the lower reaches of the Yangtze and Qiantang rivers, as well as Poyang and Dongting Lakes in China. They like to stay near the big whirlpools that form next to sandbars. It is mainly found in the Yangtze River and its tributaries, at the entrance of lakes and near the central sandbanks of the Yangtze River. The water depth is generally 10-20 meters, and the flow rate is about 1 meter per second. More in the long weeds and reeds of the sandbank, beach water activities. It is mostly found in the river with sandbanks. They are often active at the junction of forks at the head and tail of continents.
18 [19]
In the early 1980s, small groups of 2-6 heads were most common, sometimes forming clusters of up to 16 heads. But individual lipotes are often found acting alone. In groups, lipotes are usually led by a large adult or old individual, with young ones in the middle and young adults in the back. It is common to swim with finless porpoises, especially during mating.
[18]
They breathe low out of the water, often showing only the top of their head, their dorsal fins, and a small portion of their back. The breathing interval is usually 10-30 seconds, which can be several minutes for long dives. In spring, they are sometimes seen leaping out of the water. In the shallow water area, the air change is more frequent and the swimming speed is faster. In the deep water area, the breathing interval is longer and the swimming speed is slower. The Yangtze River dolphin swims at a speed of 7.5-9.7 km/h upstream and 2.7-4.9 km/h upstream upstream. Migration range of at least 200 km. Yangtze dolphins usually dive to avoid boats approaching.
[18]
The Yangtze River dolphin breathes with its lungs and comes out of the water every 10 to 100 seconds to change air. It makes a sound of "booing" and sometimes squirts water. When breathing, the top of the head and breathing hole surface first, then the back. The breathing time of the water is about 1-2 seconds, the diving time is about 20 seconds each time, and the diving time can be 200 seconds without breathing after being frightened or under special circumstances when the danger is detected. Normally, the breathing rate is 109-150 breaths per hour. When the weather is hot and heavy rain is coming, the Yangtze River dolphin often rises and falls above the water surface, so it is also called "Baijiang pig".
[17]
Yangtze River dolphin has a constant body temperature, which is around 36℃. The water temperature conditions are high, often stay in a fixed area for a period of time, and move into another area after the water temperature changes. It is used to living in the deep water area of the center of the river flow, and will also enter the confluence of lakes, tributaries and main streams. They are mainly active during the day and rest at night. Timid and shy, rarely near shore or boats.
[17]
Lipotes usually feed in the early morning and evening, and often swim to shallow water to catch fish and shrimp in the morning and evening. It uses its own ultrasonic signals to find food and swallow it in surprise. Digestive ability is very strong, catch food without chewing, swallow the whole mouth into the stomach. The food intake is large, and the daily food intake can account for 10%-12% of the total weight. The main prey is
Grass carp
,
Black carp
,
Bighead carp
,
Silver carp
,
carp
,
Megalobrama trigonata
,
squaliobar
,
Catfish
and
Yellow catfish
Let's wait. The body length of the fish eaten is more than 25 centimeters, the weight is less than 100 grams, the largest food is 50 centimeters long, the weight is 1200 grams, and the body length of the fish is not more than 6.5 centimeters.
[17]
The Baiji has lived in the muddy waters of the Yangtze River for a long time, so its vision and hearing are severely degraded, and it mainly uses sonar to recognize objects in the water. The upper respiratory tract of Yangtze River dolphin has three pairs of unique air sacs and a throat shaped like a goose's head, but it does not have the vocal cords required for land animals to sound in the air because it lives in water. Dozens of different sounds such as "answer" and "quack" can be heard by a special hydrophone. The sound emitted by Baiji usually comes in pairs of two. After the sound is emitted, it silently waits for the echo to determine the distance and size between it and the obstacle that produces the echo, and consider whether to swim to the target. It will make a new pair of sounds shortly after receiving the echo, and then quiet for a while to wait for the echo. After the second echo is received, it can analyze the direction and speed of the target swimming, which is how the Yangtze River dolphin does echolocation like an artificial sonar. With this unique sonar system, it can also often catch food in the mud at the bottom of the river, but also can emit high frequency acoustic waves that are inaudible to human ears, and communicate with its companions more than 10 kilometers away.
[17]
[20]
The Yangtze River dolphin is a unique species in the middle and lower reaches of the Yangtze River in China. Historically, the Yangtze River, which stretches from the Xiling Gorge in Yichang in the west to the mouth of the Yangtze River in Shanghai in the east, has a length of about 1,700 kilometers
Dongting Lake
,
Poyang Lake
There were even large and small lakes and river ports adjacent to the main stream of the Yangtze River
Fuchun River
Appeared.
Due to the influence of human activities such as the construction of DAMS upstream, the distribution area of Baijiang River is gradually reduced. After 1990, it disappears in Dongting Lake and Poyang Lake, and the upper limit of its distribution in the main stream of the Yangtze River also moves to Jingzhou, 170 kilometers downstream of Gezhou Dam in Yichang, and the lower limit is even more severely reduced, and it is rarely seen near Nanjing. In the three large-scale surveys organized by the Ministry of Agriculture from 1997 to 1999, there was no discovery below the lower reaches of Nanjing near Jiangyin.
In several observations from 2000 to 2004, its distribution was mainly limited to Honghu section, Jiujiang section and Tongling section of the Yangtze River. The last confirmed record of the dolphin was a carcass stranded in the Nanjing section of the river in August 2004.
[1]
[19]
Distribution map of Baiji
The natural reproduction rate of Yangtze River dolphin is very low, the female pregnancy rate in the wild is usually only 30%, and the adult female has two estrus in a year, from March to June and from September to November. The gestation period is 10-11 months, and delivery occurs in February to April of the following year. They breed every two years, with one litter and occasionally twins. The female dolphin has a cleavage, from which the breast protrudes during breastfeeding. The uterus of the female dolphin is double horn uterus, there is a nipple on each side of the reproductive hole, and the mammary gland is developed, and the young are fed by nutritious milk. The young are born different from other animals, and the tail is exposed first to avoid drowning. Newborn young lipotes are typically 80-90 cm long and their body color is darker than that of mature lipotes. The ability to eat milk is very excellent, because the female nipple is very small, long in the rear abdomen, so it must dive to the female's abdomen to find the nipple, while eating milk, swimming, but also from time to time to come out of the water to breathe once, and so on. Females also often carry their newborn calves on their flippers, caring enough to quickly retrieve them if they are scattered. The young will be suckled by the mother for 8-20 months, and they mainly swim with the mother when they are active.
[4]
[21]
Like most mammals, Lipotes are viviparous. Life expectancy is about 30 years. According to the results of anatomical study, the male lipotes are young at 0-4 years old, reach sexual maturity at 4 years old, mature at 4-12 years old, and mature at 12-20 years old. Females, on the other hand, reach sexual maturity later, at the age of six. The male estrus usually occurs twice a year from March to June and from October to December. During this period, the male animal's skin color is purplish red (red + gray), and he often breaks water and breathes impatiently; The pregnancy rate of females reaches its highest point between February and April every other year. The Yangtze River dolphin has an estimated lifespan of 20-30 years.
[22]
In captivity, male lipotes tend to masturbate by sticking their abdomen on the bottom of the pool, sticking to the wall of the pool and exposing their penis when they are in estrus due to their long-term isolation. The mating method of lipotes in the wild has been observed that the male lies on the female's back first, and then the female turns her body sideways. The male and female turn to each other with their heads, abdomens and tails facing each other, diving underwater and breathing at the same time. However, field observation is limited by natural conditions, and it is not easy to distinguish male and female. By observing the sexual masturbation behavior of male lipotes in captivity, some scholars have pointed out that male lipotes are likely to mate on top of female lipotes, but it is not known whether the changes are affected by the artificial environment.
[21-23]
With the help of its unique sonar system, Yangtze River dolphin can quickly and accurately identify location, navigate, communicate, catch food and escape from enemies, so as to maintain its reproduction. Researchers have confirmed that the echolocation capability, anti-interference, sensitivity and resolution of the Yangtze River sonar system are far superior to the world's advanced sonar technology. Therefore, the mystery of Yangtze River sonar system is studied and revealed
bionics
And the field of military science has extremely high scientific research value.
The brain weight of Yangtze River dolphin is nearly 500 grams, the cerebral cortex has complex gyrus, the central nervous system is highly developed, and the intelligence level of Yangtze River dolphin is similar to that of gorilla. The two hemispheres of the brain can be awake and asleep at the same time, respectively, and can regularly rotate. This has important research significance for the field of biology and physiology.
In addition, Yangtze River dolphin has lived in China for about 25 million years and is an ancient relict from the Miocene and Pliocene to the present, so Yangtze River dolphin is also a precious "living fossil" for human to study the evolution of cetaceans.
Yangtze River dolphin has been affected by human activities for a long time, and its population and distribution area are shrinking gradually. More than 300 million people live in China's Yangtze River basin, equivalent to 5% of the world's population, and human activities along the river are the number one reason for the decline of Yangtze River dolphins. 92% of Yangtze River dolphin specimens collected in the 20th century are from human causes of death. By the 1990s, Yangtze River dolphins had disappeared from the Dongting and Poyang Lakes. The upper limit of its distribution in the Yangtze River has also moved to the vicinity of Jingzhou, 170 kilometers downstream of Gezhou Dam. The lower limit of the reduction is more serious, and it has been found near Nanjing. In the observations from 1997 to 1999, there were no further sightings below Jiangyin, near the lower reaches of Nanjing.
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The first estimate of Lipotes abundance based on 1979-1981 quantitative survey data was made by Chinese biologist Zhou Kaiya (1982), who concluded that the total population included only about 400 lipotes. Based on a 1985-1986 survey, Chen Peixun and Hua Yuanyu (1989) made an educated guess that the total number was about 300. A survey conducted by Zhou Kaiya and Li Yuemin (1989) in 1982-1986 suggested that there were 100. The lower reaches of the Yangtze River are from Hukou to Jiangkou, and Chen Peixun and Hua Yuanyu (1989) counted 78-79 heads in the same period of time in 1985-86. Repeated surveys of a 500 km section of the lower Yangtze River (Nanjing-Hukou) in 1989-1991 produced a record of up to 12 head, which led to a study by Zhou Kaiya et al., which in 1998 inferred a total abundance of about 30 head in this section. These experts believe that if the species still inhabited the river in its historical range of about 1,700 linear kilometers, with a density similar to that within the study area, the total population in the early 1990s would have been only about 100. In the entire range of the species from 1997-1999, the largest number of lipotes was estimated (November 1997) (including one lesser lipotes) (November 1997), leading to a general belief that the abundance continued to decline and the total number was very low by then. The rate of discovery in the three-year survey has declined at a rate of about 10% per year (2003). Although there are no reliable time series counts or abundance estimates to make a rigorous assessment of trends, the vast majority of people believe that the Yangtze population declined rapidly over several decades until it could become extinct in the early 2000s.
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Sightings were recorded in 2002 (supported by photographic evidence) and the last confirmed stranding was in 2001. In several observations from 2000 to 2004, its distribution was mainly limited to the section from Dongting Lake to Tongling in the Yangtze River basin. Among them, they are mainly concentrated in three areas: Tongling section, Poyang Lake section and Honghu Section. The last known sighting of a Baiji in the wild was a stranded carcass in the Nanjing section of the Yangtze River in 2004. In November 2006 and December 2006, comprehensive visual and auditory surveys failed to locate a Yangtze River dolphin (Turvey et al., 2007). Two research vessels covered known habitats of Yangtze River dolphins from Yichang to Shanghai in both upstream and downstream directions (both sides of the river were covered). In addition, in the downstream survey, a boat towed a hydrophone to listen for the whistles and clicks of the Yangtze River dolphin. Although Dongting and Poyang Lakes were not included in the 2006 Yangtze Trunk survey, researchers studying finless dolphins in those lakes have not seen the Baiji since 2000. Another survey of finless dolphins in 2012 also failed to find any Lipotes (Mei et al., 2014).
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Chronology of population decline
The Yangtze River dolphin population was about 400 before 1984, but by 1995 it was less than 100.
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1970s: The International Union for Conservation of Nature lists the Yangtze River dolphin species as" Data deficiency (DD) "State.
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1979: The Aquatic protection Unit of the People's Republic of China listed the Yangtze River dolphin in the Red Book of Endangered Species in China and became a national first-class protected animal.
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1983: Legislation made it illegal to hunt Yangtze River dolphins.
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1984: Yangtze River dolphin protection work has been published in various Chinese newspapers and magazines, attracting the attention of the vast number of readers, and getting the reputation of "precious animal in water".
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1986: Macro estimate of total number less than 300; The International Union for Conservation of Nature changed the Yangtze River dolphin species to" Endangered (EN) "State.
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1990: Macro estimates put the total number at less than 200.
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1996: The International Union for Conservation of Nature (IUCN) upgraded the Yangtze River dolphin species to "Yangtze River Dolphin" Critical Risk (CR) "State.
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1997:23 animals were found in the annual survey, and the overall estimate was less than 50.
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1998: Only seven animals have been found in the annual survey, and the overall estimate is less than 15.
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14 July 2002: Qi Qi The last Yangtze River dolphin in captivity died in the Yangtze River Dolphin House of the Institute of Hydrology, Chinese Academy of Sciences. After extracting and preserving its DNA, its body is made into a specimen.
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2004: A dead Yangtze River dolphin was found stranded in the Nanjing section of the Yangtze River, the last time a Yangtze River dolphin was found in the wild.
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December 4, 2006: A six-week expedition of freshwater dolphins in the Yangtze River ends without finding any.
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December 13, 2006: Experts participating in the 2006 Yangtze River dolphin survey announced that the Yangtze River dolphin species may be extinct, even if a few individuals still exist, it will not be able to maintain the successful reproduction of the population. However, Chinese scholars have proposed that the Yangtze River dolphin should not be declared extinct until no live species has been observed in the wild for 50 years, according to the usual practice, and stressed that it is not appropriate to declare the species extinct under the current circumstances. [1] [4] [6] [24]
The decrease of Yangtze River dolphin abundance is caused by many factors. The most serious causes are likely to be interactions with fisheries and those resulting from the development of waters and management of navigation channels, as well as accidental deaths due to habitat loss and/or degradation. Other threats to the species' potential extinction include a certain degree of direct historical harm (for example, during China's Great Leap Forward, the traditional prestige of the Yangtze River dolphin was condemned as a "river goddess", and a factory was set up to produce leather bags using the skin of the Yangtze River dolphin, which also includes the Yangtze River dolphin, but was closed down soon after). In addition, due to ship navigation, port construction, dam repair blocking fish migration between rivers and lakes, bad land use methods, lake reclamation reducing the lake area and causing sedimentation and pollution, as well as the aggravation of water pollution in the Yangtze River, many fish eaten by the Yangtze River are seriously insufficient, destroying the living space of the Yangtze River dolphin and posing a serious threat to its population survival.
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The decreasing quantity of Yangtze River dolphin is mainly due to its poor reproduction ability and more human activities in the Yangtze River basin. Most cetacean aquatic species to which Baijiang belongs have migrated to the ocean for survival tens of thousands of years ago. The cetacean freshwater dolphin species living in freshwater basins around the earth are small in number, and the remaining five species are all endangered species. In addition, genetic studies have found that the genetic diversity of Yangtze River dolphins is very low, which also aggravates the extinction rate. Scientists have proposed ex situ conservation for this purpose.
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Fishing by fishermen in the Yangtze River basin also contributes to the death of the dolphin. Lipotes are large and often struggle to get into the nets set up by fishermen to catch small fish in the river, making it difficult to get them out of the nets in time. In order to increase the catch amount, many fishermen adopt illegal fishing methods, such as magic array and electric fishing, and occasionally the Yangtze River dolphin will unfortunately fall in the net and die, which will directly harm the Yangtze River dolphin group. Human capture is also one reason why Yangtze dolphins are endangered. Poaching or mishunting occurs from time to time, and many Baiji cannot compete with the advanced human fishing equipment and die here.
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The excessively busy water transportation on the Yangtze River, the serious pollution of the river water and the construction of a large number of water conservancy projects all threaten the living environment of the Yangtze River dolphin. In particular, the noise pollution caused by various human activities has a great impact on the Yangtze River dolphin that relies on sonar system for location detection. Many Yangtze River dolphins are buried in ship propellers. The Yangtze River is one of the most important waterways in China, with an incalculable number of ships transported every year and tens of thousands of ships equipped with propellers, which can easily cause accidents and casualties when Yangtze River dolphins collide with propellers. The Yangtze River dolphin is small, pale gray and not obvious, and is extremely difficult to distinguish in the murky Yangtze River water with a perspective of less than one meter. Lipotes have been found dead several times when large water conservancy projects are being built or when rocks are being bombed to clear waterways.
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The construction of Gezhou Dam also causes the Yangtze River dolphin distribution area to move down and the distribution density to decrease. The Three Gorges Dam, built at the outlet of the upper reaches of the Yangtze River, is not in the range of the Yangtze dolphin and has no direct impact on the Yangtze dolphin. This is because about 50% of the Yangtze River dolphin is located in a large backwater area consisting of the curved reach of the Yangtze River basin in Shishou County, Hubei Province and the curved Fanhan reach of the upper reaches of Wuhan City. When the Three Gorges Reservoir fills the upper reaches of the Yangtze River, this large backwater area will move to the upper reaches of the Yangtze River, and the sensitive Baijiang dolphin group will also move upstream; When the Three Gorges Reservoir releases water in the upper reaches of the Yangtze River, the river bed in the large backwater area is washed, and the large backwater area moves towards the lower reaches of the Yangtze River, and the dolphins also move downstream. Generally speaking, the Yangtze River dolphin can adapt to the annual seasonal movement of large backwater areas, but large-scale DAMS such as the Three Gorges Project do not discharge reservoir water according to the natural rainy and dry season, and the amount of water discharged is variable. Hydrologists therefore worry that the dolphin will not be able to adapt to the irregular changes in large backwaters. The most serious estimate put forward by scholars is that the Great backwater area may move about 150 kilometers downstream of the Yangtze River, less than a tenth of the normal range.
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On the other hand, the construction of the Three Gorges Dam has improved shipping conditions upstream, allowing for larger ships, meaning that fewer ships can be used to transport as much water as before, and the super-large reservoir has also increased the range of fish, which may help dolphins downstream. With the development of railway and road transportation, many downstream flights have been cancelled, and the probability of accidental death and injury caused by the collision between Yangtze River dolphin and ship's propeller is also reduced. The main cause of death of Yangtze River dolphin is supposed to be pollution.
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In situ conservation
The primary measure to protect the Yangtze River dolphin population is to establish a nature reserve in its active river section to strengthen in situ protection of the wild population and habitat of the Yangtze River dolphin. The main contents include the establishment of individual file of Yangtze River dolphin by photographic identification and radio mark. Monitoring the growth and decline of wild populations; The activity rule, population structure and mate system of Yangtze River dolphin were studied. We will strengthen management of shipping and fisheries, prohibit the discharge of untreated industrial waste water into inhabited waters, prohibit the use of harmful fishing gear such as rolling hooks and gillnets, and crack down on illegal fishing activities. In order to satisfy the basic ecological requirements of Yangtze River dolphin's survival and reproduction, human factors should be minimized to reduce the harm of Yangtze River dolphin.
Since 1986, China's Yangtze River Basin has gradually established five in situ nature reserves. The river valley in the protection area is open, the river channel is meander, there are a lot of sandbars in the middle of the river, and many rivers such as Xiaoqing River and Neijing River connect with the Yangtze River, which is an ideal natural environment for Yangtze River dolphin to live. The management office of the conservation area has built a temporary feeding pool and a treatment pool for rescuing injured Yangtze River dolphins. In addition, the CPC Honghu Municipal Committee and the Municipal People's Government have also set up the Fishery Police Station of Honghu Public Security Bureau, the fishery Administration Supervision and Management Station of Honghu Municipal Government, and the Yangtze River Dolphin Protection Leading Group of Honghu Municipal Government to organize a large number of professional fishermen to carry out production transformation, so as to protect the water and plant resources and create better living conditions for Yangtze River dolphins.
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Ex situ conservation
The so-called "ex situ conservation" refers to the use of harmless technology, according to a certain sex ratio and age structure, live capture of 20-25 healthy individuals of Yangtze River dolphins, transfer to another environment more suitable for their survival (semi-nature reserve), artificial conservation, and reproductive research, so as to establish a captive population of Yangtze River dolphins as a reserve for revitalizing or rebuilding wild population.
Since the rapid growth of human economic activities in the Yangtze River basin cannot be reversed in the short term, and the population of Yangtze River dolphin has been extremely reduced in the 1970s and 1980s, the Institute of Hydrobiology of Chinese Academy of Sciences and other scientific research institutions have decided to implement the resite protection of Yangtze River dolphin after in-depth research. In 1989, China successively established two semi-nature reserves, the Swan River Dolphin Reserve in Shishou, Hubei Province, and the Yangtze River Dolphin Reserve in Tongling, Anhui Province, to organize capture and transfer activities, and carry out breeding and other studies. On December 19, 1995, a female Yangtze River dolphin with a length of 229 cm was successfully captured and safely moved to the Swan River Zhou Reserve, which is also the first Yangtze River dolphin in the semi-natural reserve. However, in June 1996, when the Yangtze River flood broke out, the Yangtze River dolphin got into the hole and drowned because its body got entangled in the net. Since then, although Chinese scientists have carried out several dolphin hunting activities in the Yangtze River, hoping to find the Yangtze River dolphin for relocation protection, they have failed to find the Yangtze River dolphin.
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Legislative protection
The Regulations on Reproduction and Protection of Aquatic Resources, promulgated by The State Council in 1979, prohibit the hunting of highly protected wild animals such as Baiji. On March 24, 1984, Anhui Provincial People's Government issued the Urgent Notice on Strict Protection of Yangtze River Dolphin. Catching and killing Baiji is a crime that severely damages the country's unique and precious animal, and the perpetrators should be punished according to law, the notice said. Publicity and education activities should be carried out to protect the Yangtze River dolphin so that everyone can know it. In July 1997, the government of Honghu City, Hubei Province, China issued the Notice on Strengthening the Management of Yangtze River Dolphin Nature Reserve, delimiting and establishing 8 core, buffer and experimental areas, stipulating that fishery activities and explosive, toxic and electric fishing are prohibited in the core and buffer areas, and those who cause injury and death of Yangtze River dolphin shall be prosecuted for criminal responsibility. Passing ships are also required to slow down in this section of the river and report any washed up, stranded or injured Baiji in time. In order to better improve the ecological environment of the Yangtze River, the Ministry of Agriculture and Rural Affairs of China issued the Notice on the Scope and Time of the Ban on Fishing in Key Waters of the Yangtze River Basin, announcing that from 00:00 on January 1, 2020, China will officially implement the 10-year ban on fishing in the Yangtze River.
On December 15, 1980, the former Ministry of Posts and Telecommunications of China issued a special postage stamp and a small banknote of Yangtze River dolphin, designed by Liu Shuoren and carved by Jiang Weijie and Li Qingfa. Among them, T57 white-flag dolphin stamps, photocarving overprint, 1 set of 2, 2-1 (leisurely) face value of 8 points, 2-1 (around the bottom) face value of 60 points, white-flag dolphin small ticket, the specification is 140mm×60mm, 1.08 yuan/set.
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Yangtze River dolphin stamp
In ancient Chinese literature, Baiji is often regarded as a symbol of beauty and kindness. For example, Pu Songling's poem
The stories of Liaozhai
There are Musheng and Bai Qiulian love story, which Bai Qiulian is the white fish essence into a woman, kind-hearted. Bai Qiulian is the embodiment of the Yangtze River dolphin.
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