Scientists use all kinds of clues to piece together where endangered species once dwelled. They trace the origins of museum specimens, scrutinize old maps and scientists’ dusty notes, pick through DNA and run computer models.

To map the historic home of the Yangtze finless porpoise, a group of researchers in China turned to a different sort of record: More than a thousand years of poetry.

The creature’s Instagram-ready cuteness and aquatic acrobatics don’t just appeal to modern nature lovers, it turns out.

“Compared to fish, Yangtze finless porpoises are pretty big, and they’re active on the surface of the water, especially before thunderstorms when they’re really chasing after fish and jumping around,” said Zhigang Mei of the Chinese Academy of Sciences. “This amazing sight was hard for poets to ignore.”

Mei grew up alongside the Yangtze River and recalled elders in his community cautioning that people invited bad luck if they hurt the porpoise, which has a mouth shaped into a playful smile and a sausage-shaped body as long as a grown person.

But the threat of misfortune hasn’t shielded these freshwater whales from harm. Fewer than 1,500 remain, their population battered by decades of dam-building, pollution and fishing on the river and tributaries. Numbers have rebounded slightly in recent years, but it is still considered critically endangered by the International Union for the Conservation of Nature. The river’s other cetacean, the baiji or Yangtze River dolphin, was declared functionally extinct in 2006.

While scientists have population counts for recent years and DNA and fossils for prehistoric times, that left a large gap. To try to fill it, Mei and colleagues turned to an unorthodox source. They collected more than 700 poems containing references to the porpoise, the oldest dating to 618 in the Common Era. Then, through careful reading of the texts and accounts of the poets’ lives, they mapped where in the river’s 6,300 kilometer length the authors likely encountered the animal.

“One of the biggest challenges in this research was just the sheer number of Chinese poems out there, and the fact that every poet had such a different style,” said Mei, whose past work leans toward aquatic biology rather than literature. “We had to research each poet’s life and writing style to make sure the information we were getting was reliable.” 

In just one example, Quianlong, an 18^th century Qing Dynasty emperor and author of more than 35,000 poems, was inspired after spotting porpoises as he traveled to the city of Zhenjiang, approximately 300 kilometers upriver from the coastal city of Shanghai: “porpoises chased moonlight on silvered tides,” he wrote.

By that time, the porpoises were already showing signs of decline, at least according to where poets saw them. The sightings were most widespread during the Tang (618-907 C.E.) and Song (960-1279) dynasties, the scientists reported Monday in the journal Current Biology. In the Qing dynasty (1636-1912) the poets saw them in 10% fewer sections of the river system, with the decline occurring in tributaries and lakes. By the end of the 20^th century, the world of porpoise-touched poetry had collapsed. Between 1978 and 2000, poems noting the animal had shrunk in geographic range by 65% compared to the time of the Tang Dynasty. The most precipitous drop came in the tributaries and lakes – a 91% decline in area where they were seen.

The results are consistent with past research that found human alterations of the river, especially massive 20^th century engineering projects such as dams, are a major source of the animal’s decline. For Mei, it also revealed the poetry could serve as a tool of science. “It’s like having a conversation with the poets of the past,” he said.

Perhaps in the future, scientists will trace 21^st century losses through works of literature. When will authors stop writing of glaciers in the Lower 48 states? How often will essayists opine about swimming among dazzling coral reefs a century from now? Will the finless porpoise occasionally break the surface of the literary Yangtze?

And will poets find a more complete way to help us account for what is lost, than in a scientific paper?

Zhang, et. al. “Range contraction of the Yangtze finless porpoise inferred from classic Chinese poems.” Current Biology. May 5, 2025.

Images: photo of a Yangtze finless porpoise hunting in Poyang Lake by Yu Huigong superimposed on a a Ming Dynasty woodblock-printed illustration from “Sancai Tuhui.”