ScienceShot: The Last Sightings of the Yangtze River Dolphin

The Yangtze river dolphin, or baiji, has been presumed extinct since an intensive 2006 survey failed to find a single individual of the species. But the pattern of its last sightings is proving surprising. Scientists had thought baiji had suffered habitat range fragmentation or contraction, which would have meant sightings only in limited areas, as often occurs in threatened species. But researchers report online tomorrow in the Proceedings of The Royal Society B that fishermen recall seeing baiji all along the middle and lower Yangtze even after the population went into terminal decline in the mid-1990s. Knowing that these river dolphins occupied and traveled throughout their historical range while they succumbed to habitat loss, illegal fishing, and ship collisions won't bring them back. But the findings show that efforts to save other threatened freshwater cetaceans, including the critically endangered Yangtze finless porpoise, should be based on how remaining animals are actually using their historical range.

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