5 days ago
Captive-born porpoises released in river — and quickly make a friend. ‘Success'
Conservationists stood on the banks of a river in China and watched a pair of just-released porpoises. Years of planning and preparation had led to this moment, and an optimistic feeling filled the air.
But would this plan — a first-of-its-kind project— actually work? Would these captive-born porpoises survive?
The conservation team had a straightforward plan: Take two critically endangered Yangtze finless porpoises born in captivity, acclimate them to the natural conditions of the Yangtze River in a monitored way and then release them into the wild, according to a study published June 4 in the peer-reviewed journal Biology Letters.
This approach, known as ex situ conservation, has been used for other endangered animals but has had 'few significant successes' for cetaceans, the group that includes whales, dolphins and porpoises, researchers said. Yangtze finless porpoises are the outliers and 'currently the only cetacean subspecies' with a captive breeding population.
As researchers prepared to release the captive-born Yangtze finless porpoises into the wild, they developed a follow-up plan to monitor the reintroduction, the study said. First, they implanted identification chips. Next, they fitted the porpoises with a temporary 'wearable radio tag system' to track their locations.
The porpoises were released on April 25, 2023, into the Yangtze River at a site with 'relatively low levels of human activity,' 'abundant fish resources' and a stable local porpoise population, researchers said.
Photos shared by the Chinese government in an April 2023 news release show the porpoises being set free.
After the release, researchers continued tracking the porpoise pair with acoustic monitoring devices and visual surveys, the study said. They also partnered with the Yangtze Cetacean Protection Network to watch for dead porpoises and, if found, check their identification chips.
Three days after the release, the team spotted something encouraging: The porpoises had made a friend and 'were observed interacting with a local porpoise,' the study said. A photo shows the three animals.
Nine days after their release, 'the porpoises left the vicinity of the release site,' researchers said. Their tracking tags fell off around this time.
Almost 23 months later, the team had 'continuously monitored the river and collected reports of dead' porpoises but had not found the bodies of the two released animals, the study said.
Researchers concluded the released porpoises had survived and 'gradually integrated' into the local population. They declared the project a first-of-its-kind 'success' and 'significant advancement in the conservation of' Yangtze finless porpoises.
The research team included Jiansong Qiu, Yang Zheng, Fei Fan, Jinsong Zheng, Qiang Zeng, Zijia Xu, Qiang Gao, Kexiong Wang, Songhai Li, Ding Wang and Zhigang Mei.
