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 In the case of the saola, a handful of photos are the most that Western scientists have seen, so the 50-year rule is obsolete.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.”