Ancient poetry unveils hidden history of critically endangered finless porpoises, scientists say

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14-05-2025

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A research team in China got creative in its efforts to save a critically endangered species by turning to ancient poems. The scientists pored over more than 700 ancient Chinese poems from the Tang through the Qing dynasties that mention the Yangtze finless porpoise to find out where and when poets described seeing the animal because little is known about its population history.
The Yangtze finless porpoise — the world's only freshwater porpoise — has faced extreme declines in numbers in the past four decades. With fewer than 1,300 individuals left in the wild, scientists in eastern China have made huge efforts to better understand the animal's past habitat range to better inform future conservation initiatives.
The findings were stark: The data suggests that the historic range of the finless porpoise has shrunk by 65% over the past 1,200 years, with the most extreme reduction happening over the past century. The team published the findings in the journal Current Biology on May 5.
'Some older fishers told me they used to frequently see porpoises in areas where they've now disappeared completely,' study coauthor Zhigang Mei told CNN in an email. 'That really sparked my curiosity: Where did these porpoises historically live?'
Yangtze finless porpoises only live in the middle-lower Yangtze River basin in eastern China. From the early 1980s until the 2010s, the population steeply declined an estimated 60%, according to a 2014 study, due to a combination of illegal fishing practices, industrial pollution in waterways, dams and sand mining in the adjoining lakes.
Because hard scientific data for the porpoise only exists for recent decades, scientists have a very narrow understanding of its spatial distribution. This creates a problem known as shifting baseline syndrome, explained Mei, a professor at the Institute of Hydrobiology, Chinese Academy of Sciences, in Wuhan.
'(This research) answers important questions about what constitutes a healthy population,' he said, which will help with setting realistic management goals. 'Without historical baselines, there is a risk of shifting expectations downward over generations, accepting an ever-declining status as 'normal.''
When Mei and his colleagues started poking around archives for answers, they were surprised. Official records such as local gazettes and county chronicles didn't have any information about the porpoises — only terrestrial megafauna like tigers and elephants, species that have frequent conflict with humans.
Porpoises, in contrast, are less likely to have close encounters with humans. (No drama, no record.) Instead, sightings were typically by local, less-educated anglers or wealthy travelers — who caught glimpses of the elusive porpoises while traveling the Yangtze River by boat — and weren't formally recorded, Mei said.
Facing this dead end, the scientists realized ancient poems could come in handy.
'We were amazed,' Mei said of the researchers efforts to explore written documentation via literature.
The authors sorted through hundreds of poems dating back to AD 830 that referenced porpoises. For each poem, the scientists looked for evidence of locations, such as descriptions of unique geographical features of the Yangtze River basin. Then, the team researched the poem's time period and each poets' personal history to ensure their accuracy. About half of the poems contained precise location information, allowing the team to map sightings for each dynasty.
Ancient Chinese poetry is often nonfiction, including first-person accounts of everyday life and observations of nature, the authors explained. That's why the poems served as a reasonable metric for finless porpoise sightings throughout the river basin.
'Emerald seals the jade-green tiles as idle dawn clouds drift / Specks of porpoises vanish between the waves' swift lift,' reads one Qing Dynasty poem by Gu Silì 顾嗣立 called 'Crossing the River in Rain, Looking at Jinshan,' as translated by lead study author Yaoyao Zhang, an ecologist at the Institute of Hydrobiology, Chinese Academy of Sciences.
'It's beautiful, actually,' said Paulo Corti, a conservation ecologist at Austral University of Chile who was not involved in the research. 'They did something great with some very simple information.'
Using historic materials for science isn't uncommon — especially in paleontology or archaeology — but it's less often used for wildlife research, Corti said.
'It's a very useful tool, especially when you refine the analysis, taking those qualitative data into quantitative (data),' he said.
The poetry data only offers an estimate. However, it's the study authors' best source for formulating how the Yangtze finless porpoise population's distribution changed before modern times.
Such studies need to be conducted carefully, adds Corti, who has written journal articles about responsibly using historical records for wildlife studies after noticing that some scientists were using such data inappropriately.
One major limitation of cultural records is human error, he explained. A fisherman or hunter, for example, is a more reliable observer than a foreign explorer likely to misidentify similar-looking animals. That's why the study authors researched each poet's background, such as where they lived and traveled, to verify their observations.
The Yangtze finless porpoise looks distinct, with a short snout, dark gray color and signature lack of a dorsal fin, which sets it apart from its dolphin relatives.
As mammals, porpoises need to surface for air, making them visible to humans, said study coauthor Jiajia Liu, a professor of biodiversity science at Fudan University in Shanghai. And because finless porpoises did not historically hold cultural importance, it was less likely for poets to write about them without a literal observation, he added.
For these reasons, the researchers trusted the poems for data.
That said, the authors acknowledge that some historical references of the river porpoise could be confused with the now-extinct baiji, a freshwater dolphin that lived in the Yangtze. But this species was much bigger, lighter-colored, and touted a long snout — its most distinguishing feature, Mei said.
Indeed, the baiji serves as a cautionary tale for the finless porpoise. The freshwater dolphin already became functionally extinct in 2006 from many of the same threats.
Extinction of the finless porpoise would throw the ecosystem out of balance, Liu explained. As a top predator, the porpoise eats fish that feed on aquatic grasses. The rare mammal is also an ecosystem engineer by facilitating a process called nutrient cycling. By migrating long distances, the finless porpoise carries nitrogen and phosphorus from the river bottom to its surface, and from downstream to upstream.
Now that there is some evidence that the finless porpoise lived not only in the main river, but also in tributaries and lakes, scientists have a better idea of where the porpoise historically thrived — and whether it might thrive in those locations once again.
With captive breeding — a process in which endangered species are bred in captivity and released back into the wild — underway since 1996, the authors hope their new findings may help inform future conservation efforts, such as identifying areas where they can be released.
But it's important not to jump to conclusions, Corti warned. Using such information for modern-day wildlife management requires a thorough understanding of species behavior, morphology, diet and other factors, he said. 'You can make a lot of mistakes' extrapolating historic observational data to inform future management decisions, he added.
'If you are trying to see what happened with the species in the past, you need to know what is going on now,' Corti said.
Importantly, Mei noted, this study creates a link between endangered species and culture, which could attract public attention. If the Yangtze finless porpoise can be a flagship species, such as the panda, it will help improve their conservation, he said.
Over the past few years, the porpoise population increased for the first time, thanks in part to conservation policies such as fishing bans.
'Conservation is not only (for) scientists,' Mei said. 'It's about everyone, it's about our culture.'