Is the baiji really extinct?

On 13 August 2007, the scientific journal Biology Letters published a paper that would mark the recent history of conservation. Sam Turvey, a biologist at the Zoological Society of London, and his co-authors declared that the baiji (Lipotes vexillifer), a dolphin endemic to the Yangtze river in China, was “functionally extinct”. Not one individual was seen during the six weeks of intensive survey carried out in late 2006 by an international team over 3,500 kilometres of river. This is, as far as the researchers know, the first documented extinction of a cetacean species in modern times, and the first extinction of a large vertebrate caused by human activity since that of the Caribbean monk seal in 1952. A tragic symbol, and a warning: extinction is not an abstract event, it is happening today.

An ancient and singular cetacean

The baiji was no ordinary cetacean. It made up an entire family on its own, the Lipotidae, whose common ancestor with the other odontocetes goes back some 20-25 million years. It was one of the last four genera of freshwater dolphins in the world, along with the Ganges river dolphin in India, the boto in Amazonia and the tucuxi/Sotalia. Endemic to the Yangtze and a few of its tributaries alone, it had evolved over millions of years in a distinctive environment: a river of turbid water, with a variable current and plenty of fish.

Its adaptation to that environment ran deep. Its eyes were atrophied, barely functional: underwater visibility in the Yangtze is almost nil, and sight was of no use. Its echolocation, by contrast, was particularly well developed. Its rostrum was extremely long and slender, suited to fishing in cluttered areas. It was pale bluish grey in colour, and reached 2 to 2.5 metres for 100 to 160 kilos. In some local traditions the Chinese affectionately called it the “goddess of the Yangtze”, because it guided boats through difficult passages.

The collapse

In the 1950s, the baiji population probably numbered a few thousand individuals. In 1980 it was estimated at about 400. In 1997-1999, a systematic census identified only 13 individuals. In 2002, Qi Qi, the last individual held in captivity at the Institute of Hydrobiology in Wuhan, died without having bred. In 2006, the decisive survey found none at all.

The rate of decline was vertiginous. In some fifty years, the equivalent of two or three baiji generations, a population that had held on for millions of years was reduced to zero. This pace is among the fastest documented extinctions of a large vertebrate, and shows how quickly a species can tip from “rare” to “extinct” once the pressures become too strong.

The causes

Several factors converged to wipe out the species. Intense river traffic on the Yangtze is probably the leading cause of direct mortality. It is one of the busiest waterways in the world, with tens of thousands of vessels permanently on the move. Collisions, disturbance, acoustic interference with echolocation: all these factors made survival steadily harder.

Illegal fishing also played a massive part. For decades, despite the ban, electrofishing (which stuns fish by sending electrical discharges through the water) was practised on the Yangtze. This technique kills every animal nearby indiscriminately, baiji and porpoises included. Driftnets, multiple hooks and fish traps regularly caught baiji and caused them to drown.

Chemical pollution of the Yangtze is a third factor. Heavy industry developed massively along the river from the 1980s onwards. Discharges of heavy metals, PCBs, pesticides and other pollutants saturated the river. Cetaceans at the top of the food chain bioaccumulated these toxins to fatal levels.

The Three Gorges Dam, whose construction was completed in 2003, fragmented the natural habitat of the baiji and altered the hydrology of the river. Although the dam alone is not responsible for the extinction (already well advanced before it), it helped make any future restoration all but impossible.

Finally, overfishing of its prey deprived the baiji of its food base. The Yangtze, once home to more than 400 fish species, holds far fewer today, and several of them are extinct or critically endangered.

The 2006 expedition and its verdict

Sam Turvey and his team organised a systematic survey over 3,500 kilometres of the Yangtze between November and December 2006. Two boats fitted with hydrophones, visual observers, passive acoustic monitoring. The same methodology that had made it possible to detect the last 13 individuals in 1999. This time, nothing. No visual sighting. No characteristic acoustic signal. For six weeks they searched the whole of the historical range. The absence was total.

The conclusion published in Biology Letters in 2007 was carefully worded: “functionally extinct“. That means: if a few individuals survive, they are so few that they can no longer form a viable population. Even if they were to meet and breed, environmental pressure has removed any possibility of recovery. The extinction is irreversible.

Sightings after 2006: false hopes

Since 2006, several sightings have been reported. In August 2007, an amateur briefly filmed a cetacean in the Yangtze, identified by some as a baiji; the footage is blurred and confirmation impossible. In 2016 and 2018, similar sightings were reported without conclusive evidence. Specialists consider that these probably involve Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis), the only cetacean left in the river but itself critically endangered, with fewer than 1,000 individuals.

No authenticated photograph or acoustic recording has confirmed the survival of a baiji since 2006. The IUCN maintains the status “Critically Endangered (Possibly Extinct)” on its Red List, a technical distinction that acknowledges the absence of formal proof of complete extinction, but that changes nothing in practice.

A warning for the vaquita

The extinction of the baiji is now a reference point for understanding the potential trajectory of the Mexican vaquita (see our dedicated page). The parallels are striking: a decline documented over decades, identifiable human pressures, scientific warnings ignored, conservation measures taken too late, the failure of capture and breeding attempts. The baiji could not be saved. The vaquita may perhaps still be, but the window is extremely narrow.

In 2008 Sam Turvey wrote a moving book, Witness to Extinction: How We Failed to Save the Yangtze River Dolphin, which tells the story from the inside. It is a landmark account of what it means to “witness an extinction” as a powerless scientist, and of the lessons to be drawn for other species that can still be saved.

Sources

• Turvey, S.T. et al. (2007). “First human-caused extinction of a cetacean species?”. Biology Letters, 3.
• Smith, B.D. et al. (2017). “Lipotes vexillifer“. IUCN Red List of Threatened Species, Critically Endangered (possibly extinct).
• Turvey, S.T. (2008). Witness to Extinction: How We Failed to Save the Yangtze River Dolphin. Oxford University Press.
• Wang, K. et al. (2006). “Decline of the Baiji”. Marine Mammal Science, 22.
• Yang, G. et al. (2013). “Demographic history and genetic differentiation of an endangered Yangtze finless porpoise”. Genetics & Molecular Research.

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