第1个回答 2024-06-02
The white-fin dolphin, commonly known as the white-fin, white-sleeve, or river horse, belongs to the order Cetacea, family Delphinidae, and order Mysticeti. Its distribution is confined solely to the middle and lower reaches of the Yangtze River, with a particularly high concentration in the sections downstream of Shashi, Hubei, bordering Hunan, Hubei, Anhui, and Jiangsu provinces.
The white-fin dolphin is a rare aquatic mammal endemic to China, offering invaluable insights into the evolution of cetaceans and biological evolution. With a well-developed brain, it is an intelligent creature possessing unique abilities such as echolocation and sonar. Its streamlined body, abundant subcutaneous fat, agile swimming style, and other features hold significant scientific value in the field of biomimetics.
The white-fin dolphin has a spindle-shaped body. Its beak is extremely long and narrow, with the upper and lower jaws almost equal in length, and slightly upwardly curved. Its body length is approximately six times the length of its beak. The dolphin's back is a dark gray color, while its belly is white. There is a circular white patch on both sides of the neck, behind the ear holes, and above the dorsal fin, as well as two crescent-shaped white patches above the anal region on the tail side.
The white-fin dolphin prefers to inhabit the mainstream areas of the river away from the shore. It is a solitary species that is often seen in groups of three to five individuals. Occasionally, it may venture into lakes, tributaries, and the confluence with the main Yangtze River. It breathes air through lungs, surfacing every one to two minutes to exhale and inhale. It often emerges with its head first, sometimes spraying water and making noise when exhaling. On hot, humid days preceding heavy rain, it tends to surface more frequently, leading locals to refer to it as the "white-fin tipping river."
As a carnivorous animal, the white-fin dolphin has poor eyesight and relies on the ultrasonic signals it emits to detect food and launch surprise attacks. Its diet mainly consists of fish, often foraging in shallow areas, distributaries, and the confluence of tributaries. It has a large appetite, with its daily intake often amounting to 10% to 12% of its body weight.
Female white-fin dolphins reach sexual maturity at around 6 years old, while males at 4 years. The breeding season occurs from April to June, with a gestation period of about 9 months, resulting in births from January to February of the following year in the river. A female typically gives birth to one calf per year, occasionally twins. Newborn calves nurse on their mother's milk and accompany the group in their activities.
The construction of the Gezhouba and Three Gorges Dams has caused a drastic change in the Yangtze River ecosystem. The development of shipping, river regulation, increased motorized vessels, water pollution, silting of lakes and rivers, and the use of harmful fishing gear and methods all严重威胁 the survival of the white-fin dolphin population. Estimates suggest that fewer than 100 Yangtze white-fin dolphins remain, far fewer than the national treasure, the giant panda. To prevent the white-fin dolphin from going extinct in the wild, it has been listed as a class I protected animal in China. TheTian-e-Zhou Nature Reserve and the Anhui Tongling section of the Yangtze River have been designated as protected areas to conserve and增殖 the white-fin dolphin population, aiming to save this endangered species.