Citizen scientists collect data to aid preservation

In the Chengdu Otter Watch team, a citizen science initiative launched by Follow the River in July 2025, Yu Huan, the cofounder of the Chengdu-based social enterprise, plays a key role.

At 34, the seasoned bird-watcher and ardent nature lover is primarily responsible for conducting field surveys, monitoring Eurasian otter activities, training volunteers and documenting the animals through photography and videography.

Informed by otter sighting records the team has collected since 2021, Yu and his colleagues have chosen five monitoring areas and set up infrared cameras.

He and some of the team's volunteers regularly visit the monitoring areas and collect data from the cameras. From September 2025 to March 2026, the team obtained over 800 video records of otter activity from the five monitoring areas in Chengdu. "Public sighting records, infrared monitoring images, feces traces, DNA sequences — none of these pieces of evidence alone are sufficient," said Hu Min, another cofounder of Follow the River. "What we do is cross-verify these pieces of evidence, combine them and analyze and interpret them."

When different signals (sightings or droppings) point to the same location or repeatedly occur over time, they see not just "whether otters appear" or "a single event", but "a pattern and regularity", Hu said.

Since its launch in July last year, the project has revealed several important insights.

A female otter was repeatedly observed in a drainage channel in Dujiangyan city, suggesting it was not just a passageway but possibly a daytime resting area.

Another otter used an artificial structure on the Puyang River, running through the city, as a fixed resting point, almost like a "sofa".

The same drainage channel in Dujiangyan provided evidence of interactions between the female otter and a male otter over several days.

Their behaviors, including following, physical contact and vocalizations, were consistent with breeding behaviors. This indicated that the artificial structure might support critical life-cycle activities for otters, Yu said.

The female otter was also observed moving between different types of spaces, such as the main river, drainage channels, nearby ponds and adjacent land areas.

These fragmented habitats were connected through the otter's use of artificial structures and riverbank microtopography, allowing it to integrate disparate habitat units.

These findings demonstrated that otters could survive and adapt in highly urbanized environments, Hu said, even if the conditions were less than ideal.

On Dec 5, 2025, a friend's photos startled Yu — a series of clear footprints extended from the riverside to the waterfront promenade along the Jinjiang River in downtown Chengdu, which is the same area an otter was sighted on Dec 4, 2024.

Yu rushed to the area, walked along the Jinjiang River for a few kilometers and finally, he managed to take photos of an otter in the river.

"It suggests that Chengdu's river system likely continues to function effectively as a cohesive whole," Yu said.

He added that using photo and video materials gathered over the past year, the team plans, during the latter half of 2026, to produce a documentary about the otters living in Chengdu.

chenliang@chinadaily.com.cn