Baiji (Lipotes vexillifer)

In brief

The baiji is the first cetacean that human activity has very probably driven to extinction. Endemic to the Yangtze, the longest river in Asia, it still numbered some 6,000 individuals in the 1950s. A six-week expedition carried out in November and December 2006 over its whole range did not detect a single animal. It has never been struck off the lists: the IUCN classes it as “Critically Endangered, Possibly Extinct”, and the Society for Marine Mammalogy keeps it among the cetacean species of the world. This caution of vocabulary is not hope, it is a rule of method: declaring a species extinct demands proof that no search can supply with certainty.

Identification

The baiji was an odontocete of stocky build, bluish grey on the back and white on the belly, the boundary between the two shades remaining blurred. Its most recognisable feature was the rostrum, long, slender and distinctly upturned at the tip, set with 130 to 140 conical teeth. The dorsal fin, low and triangular, looked more like a pennant than a fin, which earned the species its epithet vexillifer, “standard-bearer” in Latin. The flippers were broad and rounded.

The eyes, minute and set very high on the head, were functional but of limited use in water where visibility was often reduced to a few centimetres. The animal relied almost entirely on its echolocation, whose clicks peaked between 70 and 100 kHz. This dependence on sound partly explains its vulnerability: in a river that had become one of the noisiest in the world, a blind dolphin deprived of its sonar is a doomed dolphin.

The most frequent confusion was with the narrow-ridged finless porpoise, which shared the same river and still survives there. The latter is smaller, uniformly dark grey, with no projecting rostrum and above all with no dorsal fin, three differences that made the distinction easy for a trained observer.

Taxonomy

The species was described in 1918 by the American zoologist Gerrit S. Miller, of the Smithsonian, from a skull and a fragment of skin brought back from Lake Dongting by the son of a diplomat. On its own it makes up the genus Lipotes and the family Lipotidae.

The baiji illustrates a remarkable phenomenon: the river dolphins of the world do not form a natural group. The Chinese baiji, the Ganges river dolphin, the Amazon river dolphin and the La Plata dolphin belong to four distinct families that colonised rivers separately. Their resemblance, elongated rostrum, flexible neck, reduced eyes, is the result of convergent evolution faced with the same constraints. Our page on freshwater cetaceans sets out this history.

The baiji lineage is an ancient one: estimates separate it from the other odontocetes by more than twenty million years. Its disappearance therefore removed not one species among others, but an entire family and an isolated branch of the odontocete tree.

Distribution and habitat

The baiji never lived anywhere other than in the Yangtze and its annexes, mainly the middle and lower course of the river, over about 1,700 km between the Three Gorges and the estuary, as well as in Lakes Dongting and Poyang and, historically, in the Qiantang river. It favoured confluence zones and the back-eddies downstream of sandbanks, where fish gather.

This river drains a basin where several hundred million people live today. It is one of the busiest river routes on the planet, and it was transformed in the 20^th century by embankment, dredging, hydroelectric development and the severing of its annexed lakes. The range of the baiji contracted from downstream and from upstream at the same time, until it amounted to no more than residual stretches.

Biology and ecology

The biology of the baiji remains poorly known, which is in itself a lesson: the species disappeared before it had been studied. Sexual maturity was estimated at six years in the female and four years in the male, with a gestation of ten to eleven months and an interval of two years between births. Births were concentrated in the first half of the year.

The animals lived in small groups of two to six individuals, sometimes more at feeding aggregations. They fed on a wide variety of freshwater fish, seized with the rostrum and then swallowed whole.

This rate of reproduction, slow even for a cetacean, deserves to be set against the mortality figures. A population that produces one calf every two years per female cannot absorb an accidental mortality of several dozen individuals a year. It is this arithmetic, and not a spectacular event, that finished the species off.

Status and conservation

The fall is documented with rare precision, and it is vertiginous.

The causes are known and ordinary. In the 1970s and 1980s, about half the documented deaths were attributable to fishing gear, in particular to the longlines of unbaited hooks that lined the bed of the river. In the 1990s, electrofishing, illegal but massively practised, accounted for about 40% of them. To these are added collisions with propellers, industrial and agricultural pollution, the scarcity of fish, and an underwater noise that saturated the one sense the animal depended on.

The attempts to save it failed for instructive reasons. A semi-natural reserve had been laid out in an isolated meander of the river, at Tian-e-Zhou, with the idea of transferring animals there: it never received baiji in sufficient numbers, the capture of individuals having proved too difficult too late. The male Qi Qi, taken in injured by hooks in 1980 and installed at the Institute of Hydrobiology in Wuhan, died there on 14 July 2002 after twenty-two years in captivity, without any breeding having been obtained. A female captured in 1995 died after six months.

The decisive expedition took place in November and December 2006, led by the Institute of Hydrobiology in Wuhan with the Swiss foundation baiji.org. Two vessels covered the known range with observers and hydrophones. No animal was detected. The result was published in Biology Letters on 7 August 2007 by Samuel Turvey and colleagues, under a title in the form of a question that was not one: first human-caused extinction of a cetacean species.

Unconfirmed reports have gone on circulating, in particular in 2007 in Anhui, in 2016, in 2018 and in 2024. None has been supported by a photograph or a usable acoustic recording. The IUCN protocol imposes a delay and a high level of proof before an extinction is pronounced, which explains why the “Possibly Extinct” tag is maintained on the Red List.

Watching this species

It is no longer possible to watch a baiji. The question nonetheless means something for the river itself: the narrow-ridged finless porpoise, the only cetacean left in the Yangtze, can still be seen there, and its numbers have risen from about 1,000 individuals in 2012 to a little more than 1,200 in 2022 thanks to reserves and to a ten-year fishing moratorium that came into force in 2021. It is the only ground for encouragement this account carries, and it shows that the measures the baiji lacked do work when they arrive in time.

The skeletons kept at the Institute of Hydrobiology in Wuhan and in a few natural history museums are today the only material trace of the species, along with the sound recordings made during the lifetime of Qi Qi.

Frequently asked questions

Is the baiji officially extinct?

No, not officially. It is classed as “Critically Endangered, Possibly Extinct” by the IUCN and still figures among the 94 cetacean species recognised by the taxonomy committee of the Society for Marine Mammalogy, where it is the only one to carry the “Possibly Extinct” tag. Since 2006 scientists have used the term functional extinction: if individuals survive, they are too few for the species to reproduce. We go into this point on our page is the baiji really extinct.

What killed the baiji?

No single event. Bycatch was the first cause, with about half the documented deaths in the 1970s and 1980s, then electrofishing in the 1990s. River traffic, pollution, the collapse of fish stocks and underwater noise did the rest. This accumulation of ordinary causes, none of them spectacular on its own, is precisely what makes the case exemplary.

How many baiji were left in 1997?

Thirteen individuals were detected during the 1997 census. Nine years later, the 2006 expedition found none.

Was the baiji blind?

No, unlike the Ganges river dolphin, whose eye has no lens. The baiji had functional eyes, but very small ones set high on the head, of reduced use in silt-laden water. It hunted by sonar.

Are there still cetaceans in the Yangtze?

Yes, one only: the narrow-ridged finless porpoise, whose river population has risen to a little more than 1,200 individuals in 2022. It remains Critically Endangered, but its trajectory has been reversed.

Why speak of an entire family lost?

Because the baiji was the only representative of the genus Lipotes and of the family Lipotidae, a lineage separated from the other odontocetes for more than twenty million years. Its disappearance removes an entire branch of the cetacean tree, and not one species among close neighbours.

Sources

• IUCN Red List, Lipotes vexillifer
• Turvey S. T. et al., 2007, “First human-caused extinction of a cetacean species?”, Biology Letters 3: 537-540
• Society for Marine Mammalogy, list of marine mammal species and subspecies
• https://en.wikipedia.org/wiki/Baiji
• https://en.wikipedia.org/wiki/Yangtze_Freshwater_Dolphin_Expedition_2006
• Natural History Museum, “The baiji: why this extinct river dolphin still matters”

Account compiled from authoritative scientific sources (IUCN, Society for Marine Mammalogy, specialist literature) and reviewed for factual accuracy.