Baijis

(Lipotidae)

Class Mammalia

Order Cetacea

Suborder Odontoceti

Family Lipotidae

Thumbnail description
Light-colored dolphin with robust body, small bluff head, tiny eyes set high on sides of head, long narrow beak slightly upturned at tip, blunt-peaked triangular dorsal fin, and broad flippers

Size
7.5–8.5 ft (2.3–2.5 m); 290–370 lb (130–170 kg)

Number of genera, species
1 genus; 1 species

Habitat
Freshwater, rivers, and lakes

Conservation status
Critically Endangered

Distribution
Yangtze River of China, from Three Gorges to the sea, including tributary lake systems

Evolution and systematics

Although the genus Prolipotes was assigned to a mandible fragment from the Miocene of China, Fordyce and Muizon considered this fossil specimen to be non-diagnostic and therefore incertae sedis. The only good fossil cranial material for a lipotid, belonging to the extremely long-beaked genus Parapontoporia, comes from the latest Miocene (6–8 million years ago [mya]) to Late Pliocene (2–4 mya) of Mexico and California. Based on the fact that lipotids are known only from the Northern Hemisphere, and there only from China (the living baiji) and western North America (the long-extinct Parapontoporia), it is provisionally assumed that the evolutionary history of Lipotidae took place in the North Pacific.

The genus Lipotes was traditionally classified in either of two families of long-beaked river dolphins—Platanistidae or Iniidae. In 1978 Zhou et al. proposed that it be assigned to a separate family, Lipotidae, on the basis of osteology and stomach anatomy. Although Barnes later placed Lipotes in a subfamily of Pontoporiidae, the current consensus supports placement of Lipotes and Parapontoporia in their own family, Lipotidae. Until recently, the four living genera of long-beaked "river dolphins"—Platanista, Inia, Lipotes, and Pontoporia—were lumped together in Simpson's superfamily Platanistoidea. However, it is now recognized that only Platanista, the Ganges and Indus dolphin of the south Asian subcontinent, belongs in that superfamily. Muizon has assigned Lipotes and Parapontoporia to the monofamilial superfamily Lipotoidea.

The taxonomy of this species is Lipotes vexillifer Miller, 1918, Tung Ting Lake, about 600 mi (965 km) up the Yangtze River, China. Other common names include: English: Chinese lake dolphin, white fin dolphin, French: Baiji, dauphin fluvia de Chine; Spanish: Baiji, delfín de China.

Physical characteristics

The baiji (Lipotes vexillifer) has a spindle-shaped, robust body, with a rounded, rather bluff melon (forehead) and a very long, narrow beak. The beak is often slightly upturned at the tip. There are 30–34 teeth in each of the upper jaws and 32–36 in the lower jaws. The eyes are small, regressed, and dark, situated high on the sides of the head. The oval-shaped blowhole is oriented longitudinally on top of the head, slightly left of the midline. The baiji's dorsal fin is low and triangular, its flippers broad and rounded at the tips.

The baiji's coloration is a subtle blend of gray, bluish gray, and white. Basically, the dorsal surfaces are gray or bluish gray, the ventral surfaces white or ashy white. A broad, irregular white stripe sweeps up onto each side ahead of the flipper, and two more brush strokes of white intrude onto the gray sides of the tail stock.

Distribution

The baiji is endemic to the Yangtze River of China. Its historical distribution extended for approximately 995 mi (1,600 km), from the Yangtze estuary upstream to the Three Gorges above Yichang (655 ft [200 m] above sea level). During floods, dolphins also entered the two large tributary lakes of the Yangtze—Dongting and Poyang. During the great flood of 1955, a few specimens were reported in the Fuchun River, which flows into the East China Sea to the south of the Yangtze mouth. In recent years, there have been no observations upstream of Shashi, which is about 93 mi (150 km) below the Gezhouba Dam, which in turn is about 30 mi (50 km) downstream of the Three Gorges.

Habitat

Within the Yangtze system, the baiji shows a strong preference for eddy countercurrents that form below meanders

and channel convergences. Therefore, prime areas for finding these dolphins tend to be near sandbanks, just below islands, and where tributary streams enter or lakes connect with the main channel.

Behavior

There has been little opportunity to study the baiji's behavior in the wild, particularly over the last decade or two when just finding a few animals has been a major challenge. Group size ranges from two to seven; groups occasionally form temporary aggregations of 15–20. Although baiji generally do not breach or exhibit aerial activity of any sort, they typically expose the head and beak on the first surfacing after a dive. Dives can last one to two minutes. These dolphins are strong swimmers; several animals were observed to move 60 mi (100 km) upriver against the Yangtze's current in just three days.

Feeding ecology and diet

Based on stomach contents of wild dolphins as well as the behavior of captives, the baiji's diet it believed to consist entirely of small fish. It consumes a large variety of species, the only limitation appearing to be the size of its mouth and throat. Most fish eaten are less than 2.6 in (6.5 cm) long and weigh less than 9 oz (250 g). Fish are ingested whole and headfirst.

Reproductive biology

Little is known because no observational research on baiji reproduction has been conducted. All that is known about the species' reproductive biology has come from examinations of specimens collected opportunistically, most of them killed incidentally in fishing gear. Females apparently become sexually mature at a body length greater than 6.5 ft (2m). Males of approximately that length have mature, active testes. Single calves, about 3 ft (91 cm) long, are born mainly in spring, following gestation period of probably 10–11 months. Age at sexual maturation is about six (females) or seven (males) years.

Conservation status

The baiji is the most endangered species of cetacean, numbering only a few tens of individuals. It has probably been declining in abundance and range for a very long time, but there is little reliable information on absolute abundance or trends for any time period. Dolphins apparently were still common and widely distributed in the Yangtze when China's Great Leap Forward began in 1958. Intensive hunting for meat, oil, and leather ensued. Purchasing stations along the river received dead cetaceans from fishermen and supplied them to a central leather factory where bags and gloves were produced from baiji skin. A few hundred animals are believed to have survived as recently as the late 1970s, but the main threats—incidental mortality in fisheries, heavy vessel traffic, declining prey resources, and pollution—have continued unabated.

Since 1986, efforts have been made within China to develop "semi-natural reserves," with the intention of providing safe refuges for dolphins. These reserves were expected to provide opportunities for captive breeding and eventual restocking of the river. However, only one animal was captured—an adult female translocated to the Shishou Baiji Semi-natural Reserve near Wuhan in December 1995. She survived for six months, and during that time no effort was made to place her with the other captive baiji, a male that had been salvaged after becoming hooked and entangled in fishing line in 1980. This male died in 2002.

Despite full legal protection from deliberate harm since 1983, the baiji appears doomed. Its habitat has become thoroughly dominated by humans, and there is abundant evidence that intensive human use of the Yangtze is incompatible with the dolphin's survival.

Significance to humans

The baiji is characterized in Chinese folklore as "Goddess of the Yangtze." Legends and myths portray the dolphin as a friendly and beneficent creature, and it was long revered by fishing people along the Yangtze. Thus, the wanton killing of the late 1950s and 1960s went against traditional cultural norms and probably can be viewed as an aberration.

"Qi Qi," the male baiji held at the Wuhan Institute of Hydrobiology from 1980 to 2002, was a symbol of hope for the species. Most published baiji photographs and video footage depict "Qi Qi" in his tank. The symbolic importance of the baiji to aquatic conservation in China may be likened to that of the giant panda (Ailuropoda melanoleuca) to forest conservation. It appears, however, that the baiji will become extinct long before the giant panda, if for no other reason than because it has proven impossible to find, capture, and maintain significant numbers of these dolphins in captivity.

Resources

Books

Chen, P. "Baiji Lipotes vexillifer Miller, 1918." In Handbook of Marine Mammals. Vol. 4, River Dolphins and the Larger Toothed Whales, edited by S. H. Ridgway and R. Harrison. London: Academic Press, 1989.

de Muizon, C. "River Dolphins, Evolutionary History." In Encyclopedia of Marine Mammals, edited by W.F. Perrin, B. Würsig, and J. G. M. Thewissen. San Diego: Academic Press, 2002.

Perrin, W. F., R. L. Brownell Jr., K. Zhou, and J. Liu, eds. Biology and Conservation of the River Dolphins: Occasional Papers of the IUCN Species Survival Commission No. 3. Gland, Switzerland: IUCN, 1989.

Reeves, R. R., B. D. Smith, and T. Kasuya, eds. Biology and Conservation of Freshwater Cetaceans in Asia: Occasional Papers of the IUCN Species Survival Commission No. 23. Gland, Switzerland: IUCN, 2000.

Reeves, R. R., B. S. Stewart, P. J. Clapham, and J. A. Powell. National Audubon Society Guide to Marine Mammals of the World. New York: Alfred A. Knopf, 2002.

Zhou, K. "Baiji Lipotes vexillifer." In Encyclopedia of Marine Mammals, edited by W. F. Perrin, B. Würsig, and J.G.M. Thewissen. San Diego: Academic Press, 2002.

Zhou, K., and Zhang, X. Baiji, the Yangtze River Dolphin and other Endangered Animals of China. Washington: Stone Wall Press, 1991.

Periodicals

Zhou, K., J. Sun, A. Gao, and B. Würsig. "Baiji (Lipotes vexillifer) in the Lower Yangtze River: Movements, Numbers, Threats and Conservation Needs." Aquatic Mammals 24 (1998): 123–132.

Zhou, K., W. Qian, and Y. Li. "Recent Advances in the Study of the Baiji, Lipotes vexillifer." Journal of Nanjing Normal College (Natural Sciences) 1 (1978): 8–13.

Randall Reeves, PhD