Lipotes vexillifer

Geographic Range

Lipotes vexillifer , also known by the common name baiji, is found in China in the mouth of the Chang Jiang (Yangtze) to a point about 1900 km up the river, as well as in the middle and lower regions of the Quintangjiang River and in the Dongting and Poyang lakes.

• Biogeographic Regions
• palearctic palearctic
  • native native

Habitat

Baiji are freshwater dolphins that inhabit the lower reaches of China's Yangtze and Quintangjiang rivers, and in the Poyang and Dongting lakes. They prefer to stay near large eddies that form next to sandbars.

• Habitat Regions
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Other Habitat Features
• riparian riparian
• estuarine estuarine

Physical Description

Baiji, like other dolphins, have streamlined, fusiform bodies. They have rounded flippers and long, beaklike, upturned snouts, which are completely hairless. Their small but functional eyes sit high on their heads, and their blowholes are elliptical and oriented longitudinally. Baiji are pale blue-grey dorsally and white ventrally. They have 30-36 teeth per side of both the upper and lower jaws. Baiji have no fore-stomachs but their main stomachs consist of three chambers, and they lack ceca. The skulls of these dolphins lack maxillary crests, and the palatal portions of the maxillae contact one another.

Female baiji are larger than males. Females range from 185 to 253 cm in length and weigh 64-167 kg, while males range from 141 to 216 cm in length and weigh 42-125 kg.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

The mating system of baiji is unknown.

Little is known about the reproductive activities of baiji. Ovulation in females is periodic and sperm density in males varies seasonally. The mating season peaks twice a year, in spring and in autumn. The gestation period estimates range from 6 to 12 months. Females give birth to one 80 cm long calf every two years. Baiji reach sexual maturity at 3 to 8 years of age.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Mothers carry their calves close to the side of their bodies while swimming, diving, and coming up to breathe. It is unknown how long they nurse their young, and whether there is any association between mother and offspring after the young are weaned.

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

One wild-caught baiji was estimated to be 24 years of age; this number provides a minimum estimate of the lifespan of this species.

Behavior

Due to their cryptic habits, much of the behavior of baiji remains a mystery. They are usually found in pairs, which aggregate to form larger social units of about 10 individuals. Most of their time is spent in the vicinity of large eddies, where they search for fish during the day. At night they rest in areas of slow current. The population density in the Quintangjiang was estimated (in 1978 and 1980) at one Baiji every 4 km.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• social social

Communication and Perception

In the turbid waters of the Yangtze, vision is mostly useless, so baiji use echolocation to navigate and find food. They communicate with one another using whistles and other acoustic signals.

• Communication Channels
• acoustic acoustic

• Perception Channels
• tactile tactile
• acoustic acoustic
• echolocation echolocation
• chemical chemical

Food Habits

The diet of baiji consists of mainly, if not entirely, of fish. They use their long beaks to probe muddy bottoms for food. Their dives are short, lasting only 10-20 seconds. Baiji have poor eyesight but use a highly developed echolocation faculty to find food. These creatures seek food in the shallow water near sandbanks or close to the mouth of tributaries of the river.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• fish

Predation

There are no reports of predation on baiji, except by humans.

Ecosystem Roles

Baiji are top-level consumers in the Yangtze ecosystem.

Economic Importance for Humans: Positive

Baiji are important culturally as they have long been protected by custom. In the past, the fat of accidentally killed individuals was used for medicinal purposes and the flesh consumed. The current plight of baiji--designated a national treasure "of the first order" by China--has raised awareness of the need for conservation of river systems worldwide.

• Positive Impacts
• food food
• source of medicine or drug source of medicine or drug
• research and education

Economic Importance for Humans: Negative

Baiji have no known negative effects on humans.

Conservation Status

Lipotes vexillifer is probably the most endangered of all cetaceans. It is listed as critically endangered on the IUCN's Red List of Threatened Species, it is listed as endangered by the U.S. Fish and Wildlife Service, and it is on CITES appendix I. The total population is estimated at less than 100 animals; surveys in the late 1990s put the minimum population estimate at 13. A 2006 survey of the entire range of L. vexillifer failed to find any individuals at all, and it is probable that the species is now extinct.

There are three major factors that threaten baiji survival: dams and floodgates that block fish migration in the river's tributaries and lakes, fisheries accidentally killing dolphins, and boat propellers. Population numbers also declined through hunting and development of irrigation facilities. The heavy pollution and underwater noise characteristic of the Yangtze also affects the Baiji. These stresses, as well as lack of food, can inhibit reproduction.

China began providing legal protection in 1975. Programs are being established to breed Lipotes vexillifer in captivity, though no one has yet succeeded at housing wild baiji for long. In 1992 an oxbow jutting off from the main Yangtze river was set aside as a reserve where baiji could be relocated and allowed to live under semi-natural conditions. In the face of ongoing degradation of the Yangtze river, this "ex-situ" conservation strategy may be the species' only hope for survival. In 2006, a survey of the entire range of baiji will be carried out by the baiji.org foundation in collaboration with Chinese administrators and the Institute for Hydrobiology. Scientists are hopeful this survey will give them a better idea of exactly how many baiji remain and where they are located, so that they can eventually be relocated to reserves.

Additional Links

Encyclopedia of Life

Contributors

Allison Poor (author, editor), University of Michigan-Ann Arbor.

Sarah Grigg (author), University of Michigan-Ann Arbor.

References

Nowak, R. 1999. Walker's Mammals of the World, vol. II . Baltimore: The Johns Hopkins University Press.

baiji.org Foundation, 2006. "The baiji.org Foundation" (On-line). Accessed January 11, 2007 at www.baiji.org .

Ames, M.H. "Saving some cetaceans may require breeding in captivity". Bioscience. vol. 41, 746-9.

Balcomb, K.C., Foster, L., and Minasian, S.M. 1984. The World's Whales: The Complete Illustrated Guide. W.W. Norton

Co.: New York.

Bryden, M.M. and Harrison, R. 1986. Research on Dolphins. Clarendon Press: Oxford.

Grzmek's Encyclopedia of Mammals. vol. 4. 1990. McGraw-Hill Publishing Co.: New York.

Nowak, R.M. 1991. Walker's Mammals of the World. Fifth Edition. vol. II. John's Hopkins University Press: Baltimore.