Rebuilding the critically endangered Yangtze finless porpoise population: successful release from an ex situ conservation programme.

Ex situ conservation and population reinforcements or reintroductions are vital strategies for protecting endangered species, yet efforts for cetaceans have been notably limited. Through post-release monitoring based on wearable radio tag and passive acoustic methods, we report the first successful release of a critically endangered small toothed whale, the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), into the wild. Our monitoring results indicate that, by the third day after release, the two porpoises from the ex situ population had joined a local individual and gradually integrated into the core distribution area of the local population. Continuous monitoring by the Yangtze Cetacean Protection Network revealed no recorded deaths among the released porpoises. This successful release demonstrates the potential of this approach as a supplementary measure for the restoration of the Yangtze finless porpoise wild population.