South China's Hainan province launches the initial follow-up survey mission on July 4 after the release of the short-finned pilot whale Haitang back into the ocean on May 26. [Photo by Wang Chenglong/For chinadaily.com.cn]

Marine experts have confirmed that the short-finned pilot whale named Haitang, which was stranded with injuries in Haitang Bay in Sanya, Hainan province on Jan 3, has returned to its normal habitat.

The island province initiated the first follow-up survey activity on July 4 following the release of the short-finned pilot whale back into the sea on May 26.

Short-finned pilot whales are nationally protected second-class wild animals in China. They are social deep-diving cetaceans. "Returning to the ocean does not mean returning home," said Li Songhai, a researcher at the Institute of Deep-sea Science of the Chinese Academy of Sciences.

Li is particularly concerned about Haitang's diving depth, worrying about its integration into the group. The analysis of the data from the signal tag on Haitang relieved his concerns. It shows that Haitang has gradually adapted to the wild environment, swimming toward the typical habitat of short-finned pilot whales. The maximum diving depth has increased from initially just a few meters to frequent dives in the range of 300 to 500 meters, reaching the deep-sea seabed where these deep-diving cetaceans forage.

"During this survey, we did not see Haitang, but we have confirmed its well-being," said Li.

"In the three-day journey, 12 hours of daily observations were conducted to verify the feedback from the signal tag. Within the area where Haitang has been frequently spotted, multiple short-finned pilot whale groups were discovered, with a total count reaching several hundred individuals, he added.