Chinese name: Baiji dolphin Latin scientific name: Lipotes vexillifer (Miller, 19 18).
Common name: white dolphin, baiji dolphin and white flag, referred to as "white dolphin"
English name: Yangtze dolphin
Grade of national key protected animals: Grade I (1995 is classified as Grade I endangered animals).
IUCN: Endangered
Endemic species: Yes.
Endangered level: endangered animals
Convention on International Trade in Endangered Species of Animals and Plants: Appendix I
Ecological environment: the intersection of fresh water and salty fresh water.
Risk factors: migration is cut off, overfishing, environmental pollution and busy shipping.
Protection measures: ex-situ protection
Domestic distribution: Yangtze River and Qiantang River [Dongting Lake and the middle and lower reaches of the Yangtze River]
Classification status:
Animals in the animal kingdom
chordata
mammal
cetacean
Tooth jaw suborder
White-fin dolphin family
Lipopods of the genus baiji
White fin dolphin species L. vexillifer
Edit the shape characteristics of this paragraph.
Baiji dolphin is spindle-shaped, about 2-2.5 meters long and can weigh more than 200 kilograms. The mouth is slender, the back is light gray or blue, the abdomen is pure white, the dorsal fin is small triangle, the pectoral fin is like two palms, the caudal fin is flat and bifurcated in the middle, and it is good at swimming, with a speed of about 80 kilometers per hour. Due to long-term living in muddy rivers, the audio-visual organs of Baiji dolphin have deteriorated. Its eyes are as small as a blind person, and its ear holes are like needle eyes, which are located at the back and bottom of both eyes. But the brain is particularly developed, the sonar system is extremely sensitive, and the head also has ultrasonic function, which can quickly transmit the sound within tens of thousands of meters on the river to the brain. In case of emergency, dive for shelter immediately. Baiji dolphin is cold-tolerant, and its body temperature is usually around 36℃.
Edit the distribution scope of this paragraph
Baiji dolphin mainly lives in the middle and lower reaches of the Yangtze River and its connected waters, such as Dongting Lake, Poyang Lake and Qiantang River. Usually in pairs or above 10, they like to move in deep water and fast water. The existing number is scarce. It was estimated that there were only about 300 heads 20 years ago, and it was on the verge of extinction.
Edit the living habits of this paragraph.
Like to live in groups, especially in the spring mating season, group behavior is more obvious. Each group is generally 2- 16. It has a wide range of activities, but it needs high water temperature. It often stays in a fixed area for a period of time, and then moves to another area after the water temperature changes. Feed on fish.
Like to live in the deep waters of rivers, rarely near the shore and ships, but it often swims to shallow waters, chasing fish and shrimp to satisfy its hunger. Its snout is wide and slender, and there are more than 130 conical teeth in the upper and lower jaws, but it is too lazy to chew, just swallowing fish food with its mouth open, and its digestion ability is very strong. Baiji dolphin often moves together in groups of three or five or in pairs, but people rarely get a chance to see it, only when it comes out of the water to breathe.
Baiji dolphins are distributed in the middle and lower reaches of the Yangtze River, about 1, 600 km from Zhicheng, Hubei Province to the Yangtze River estuary. They eat fish and like social activities. There are about 2-3 small groups, 9-65,438+06 large groups. Baiji dolphin is an aquatic mammal that breathes with its lungs. Every time he breathes, the top of his head and breathing holes first emerge from the water, and then his back and low triangular dorsal fin are exposed. The breathing time of the water is about 1-2 seconds, each diving time is about 20 seconds, and the long-term diving can reach 200 seconds. Mature individuals is generally the longest, 2.5 meters for females and 2.3 meters for males, and weighs 100 ~ 150 kg. It has a constant body temperature, always around 36 degrees Celsius.
Edit the reproductive habits of this paragraph.
Baiji dolphins breed every two years, each offspring 1, and the body length is about 80 cm at birth. Newborn larvae are slightly darker in color. Adult baiji generally has a light bluish gray back and a clean white abdomen, which is particularly bright in the sun. The upper and lower surfaces of horizontally extending flippers and caudal fins are the same color as the back and ventral surfaces, respectively, so the color distribution is just in line with the environmental color. Looking down from the water surface, it is difficult to distinguish the bluish gray on the back from the river water; Looking up from the bottom of the water, it is difficult to find that the white belly is similar to the strong light reflected from the water surface. This makes the baiji have a natural hidden barrier when fleeing from the enemy and approaching the prey. The life span of baiji dolphin can reach more than 30 years. Generally speaking, females reach sexual maturity at the age of 6 and males at the age of 4. Adult baiji is in estrus twice a year, from March to May and from August to 10. The gestation period is10-1month, with one litter and occasionally two litters. In the wild, the male-female ratio of adult baiji is 1: 1, but the pregnancy rate of females is generally only 30%, and the natural reproduction rate is very low.
The mating period of baiji dolphins is from late winter to early spring every year, and the pregnant period of female dolphins is about 1 year, so most young dolphins are born in the spring of the following year. After birth, Xiaobai and Dolphin were fed by their mother's milk and didn't mature until they were five or six years old. The average life expectancy is 30 years.
Edit the body structure of this paragraph.
Baiji dolphin is a carnivore, with about 130 sharp teeth in its mouth, belonging to the same type. Often swim to the shallow water on the shore in the early morning and evening to hunt. Generally speaking, the whole freshwater fish with a body length of less than 6.5 cm is the main food, and a small amount of aquatic plants and insects are also eaten. When breathing, the head comes out first, then all the water comes out, 2 meters upstream of the water surface, and then enters the water. Baiji dolphin's vision is almost zero, and it has extensive scientific research value in biology, bionics and physiology by relying on echolocation to understand environmental changes. However, baiji is timid by nature and easily frightened. Generally far away from the ship, it is difficult to get close. In addition, it has a small population and a wide range of activities, so the research on baiji in the wild is very limited.
The skin of baiji is smooth and delicate, and it has a special elasticity. The principle is the same as the elastic nylon fabric used in competitive swimming suits, which can reduce the turbulence around the body when swimming fast in water. Its caudal fin is divided into two forks, the pectoral fin on both sides is flat palm-shaped and the dorsal fin is triangular. These four fins provide excellent direction and balance control for baiji swimming in the water. Coupled with smooth and elastic skin and streamlined body, baiji can swim at a speed of 60 kilometers per hour when avoiding danger. Usually, it maintains a swimming speed of 10 to 15 kilometers per hour.
The baiji dolphin has lived in the turbid water of the Yangtze River for a long time, so its vision and hearing are seriously degraded. In water, it mainly uses sonar to receive signals to identify objects. The upper respiratory tract of baiji has three pairs of unique airbags and a throat shaped like a goose's head, but because it lives in water and makes sounds by water, it doesn't have the vocal cords needed by land animals to make sounds in the air. Through a special hydrophone, you can hear dozens of different sounds, such as the "answer" and "quack" sounds made by the baiji. Baiji dolphins often make sounds in pairs. After making a sound, they will wait for the echo quietly, so as to distinguish the distance and size between themselves and the obstacle that produces the echo and consider whether to swim to the target. It will make a new pair of sounds soon after receiving the echo, and then wait for the echo quietly for a while. After receiving the second echo, it can analyze the swimming direction and speed of the target. This is how the baiji locates the echo like an artificial sonar. With this unique sonar system, it can often catch food in the mud at the bottom of the river, and it can also send out high-frequency sound waves that people can't hear, and contact companions more than ten kilometers away.
The brain surface area of baiji dolphin is larger than that of dolphins, and the brain weight accounts for about 0.5% of the whole. Among them, the average weight of a male dolphin weighing 95 kilograms is 470 grams. This weight is close to the brain weight of gorillas and chimpanzees, and some scholars even think that baiji is smarter than gibbons and chimpanzees.