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發表於 2019-12-2 14:39:17
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But Yagi acknowledges that the photographs he took 23 years ago are not the definitive proof he needs.
Now, the search is turning to modern technology to help capture further proof, including about 70 motion-sensitive infra-red video cameras set up across the Okuchichibu mountains. About a year ago, they recorded footage of three deer running past one of these camera. At first it seemed little to be excited about, but on closer inspection, Yagi noticed the audio accompanying the images appears to have picked up the sound of a howl.
“We brought the recorded howl to a specialist, and he compared it to that of the Eastern wolf that was kept at Asahikawa Zoo in Hokkaido,” says Yagi. “He declared with 99.5% assurance that the two were of the same animal, and I have received a certificate of authenticity for the wolf recording.”
“When I first heard the howl 50 years ago, I had told many people that I believed it was the wolf,” says Yagi. “But their logic was that ‘If it doesn’t exist, it can't be’. Whereas I believe in its opposite – if it is, then it exists. And it is this disbelief in other people, its this idea to disprove their logic, that has driven me this far. Sometimes it does seem like the road is still long.”
‘Lazarus’ species
Historically, the IUCN used the "50-year rule" to determine whether a species or subspecies is extinct, although it has now been replaced by a more nuanced species-specific approach, which requires evidence to be collected from targeted surveys across a species' range before extinction can be determined. The reality is that for some species, which are widely tracked and extensively researched, 50 years without observation is an unnecessarily long time.
For others there might have been so few sightings of the animals in the first place it would be an arbitrarily unfair rule. “No Western scientists have ever seen a wild saola – a beautiful long-horned Asian forest antelope, which is one of the world's rarest mammals,” says Samuel Turvey from the Zoological Society of London’s Institute of Zoology. “Information about its distribution in Vietnam and Laos is based largely on anecdotal reports by local hunters and villagers.” In the case of the saola, a handful of photos are the most that Western scientists have seen, so the 50-year rule is obsolete.
“In some cases, possibly extinct species might occur in extremely remote and impenetrable landscapes which are rarely visited by researchers, and so their status remains unknown rather than necessarily extinct,” says Turvey. “The complexity of proving extinction is made more difficult by the theoretical challenges that you can't prove a negative... just because you don't find a species, does this just mean that you haven't looked hard enough, or in the right place or at the right time of year, rather than necessarily meaning it no longer exists?”
Turvey warns that in the absence of definite accepted sightings in over a century, the continued survival of the Japanese wolf is unlikely, but not necessarily impossible.
“Making its survival less likely is the fact that wolves are social animals, which live in groups and make loud howling calls, which would be expected to make them more easily detectable compared to a solitary silent animal if they were still present in a landscape,” says Turvey.
“This brings us onto the sticky issue of data quantity versus data quality. Sightings have been reported which post-date the last ‘definite’ record, but they're unverified and probably unverifiable, so we can't be sure what was actually seen. This is the same confusing situation faced by scientists when trying to determine the possible survival of other ‘officially’ extinct species such as the thylacine and ivory-billed woodpecker.”
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