Lipotes vexilliferbaiji(Also: Yangtze river dolphin)

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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. (Nowak, 1999)

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. (Nowak, 1999)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

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. (Nowak, 1999)

  • Sexual Dimorphism
  • female larger
  • Range mass
    42 to 167 kg
    92.51 to 367.84 lb
  • Range length
    141 to 253 cm
    55.51 to 99.61 in

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. (Nowak, 1999)

  • Breeding interval
    Female baiji breed once every two years.
  • Breeding season
    The mating season peaks twice a year, in spring and in autumn.
  • Range number of offspring
    1 to 1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    6 to 12 months
  • Range age at sexual or reproductive maturity (female)
    3 to 8 years
  • Range age at sexual or reproductive maturity (male)
    3 to 8 years

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. (Nowak, 1999)

  • Range lifespan
    Status: wild
    24 (low) years

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. (Nowak, 1999)

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. (Nowak, 1999)

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.

  • 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. (baiji.org Foundation, 2006)

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. (baiji.org Foundation, 2006; Nowak, 1999)

Contributors

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

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

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

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.

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.