Baiijia River Dolphin
The baiji is one of the world's rarest mammals.
It is believed that about 20 million years ago the baiji Chinese river dolphin left the ocean and made its home in the Yangtze River in China. Writings from the time of the Han Dynasty in 200 B.C. suggest that several thousands of these animals may have inhabited the Yangtze at that time. Today, researchers estimate that there are probably fewer than 100 baiji in the river, making it the most endangered cetacean in the world.
Habitat destruction and intrusion by humans has been costly to the baiji population. Pollution of the Yangtze river and depleted food sources, coupled with increased boating traffic, have taken their toll on the animals. Many have died in boat collisions.
In the past, the baiji had been protected by custom, since the Chinese considered it to be an incarnation of a drowned princess (Burton & Pearson 1987). It also has a nickname in China - "Giant Panda of the Yangtze River" - that may reflect the general affection for this aquatic mammal (Tan 1996).
In one area where the baiji is most common (Anhui Province) a council has been set up called the ?Lipotes vexillifer Conservation Association.' The association is to spread information about the baiji, especially among fishermen along the Yangtze River. An increased awareness of the baiji may have accounted for the rescue of several animals which had been hit by propellers. (Klinowska 1991)
The baiji's pectoral fins are light gray above and white below, hence the name "white-fin" dolphin. The baiji is sometimes erroneously called the "white-flag" dolphin in English, because "flag" and "fin" are both pronounced the same in Chinese, so foreigners may translate its name either as "white-fin" dolphin or as "white-flag" dolphin. (Tan 1996)
The baiji weighs 135 - 230 kg (300 - 510 lb) and measures as much as 2.5 m (8.2’) in length. It occurs in freshwater rivers and lakes and prefers large counter-currents such as are found below meanders, channel convergences, and areas in a river with structure (such as sandbars and areas adjacent to islands). It feeds on various species of small fish. As opposed to some other freshwater dolphins, like the Indus River dolphin, its eyes are functional, although greatly reduced. The baiji usually occurs in small groups of 2 - 6, which may make up a larger social unit of up to 16 dolphins. During periods of high river flow, it migrates upstream into lakes and smaller rivers.
The distribution of the baiji originally included the lower and middle reaches of the Yangtze River down to the river?s mouth, as well as several nearby lakes and rivers. The upstream boundary of the baiji’s historic distribution was located just above Yichang, where the Three Gorges formed a geographic barrier. It currently only occurs in the mainstem of the Yangtze River, and the extent of its distribution is significantly reduced.
As a habitat for the baiji, the Yangtze River has been degraded in many ways, including chemical and noise pollution and risk of physical damage due to ship collisions, blasting in the river and accidental entrapment in fishing gear. The Three Gorges Dam, currently under construction, will produce further stress on the baiji population. The dam’s operation will cause alteration of the river’s hydrological regime, which will affect the baiji’s habitat. The baiji generally occurs in large counter-currents, such as are found below meanders and channel convergences. Erosion from the water released below the dam is expected to eliminate or degrade these counter-currents for approximately 360 km (220 mi) downstream. It is predicted by local experts that the baiji will become extinct in the near future whether the Three Gorges Dam is built or not.
