How do we know that a species has definitely gone extinct (as opposed to just being extremely rare/elusive)?
In: Biology
Quick shout out to ‘Extinct or Alive’, a show on Animal Planet that shows this exact question and in my opinion is really well done.
Basically, when we don’t see any members of the species for a while. They could be extinct, or they could be good at hiding. The Zanzibar leopard is an example that is or was thought to be extinct, but there is some evidence to suggest they may still be alive and just really good at living around humans without being seen.
I know that when you’re investigating how many different species there are in an enviroment, you can use [rarefaction](https://en.m.wikipedia.org/wiki/Rarefaction_(ecology)) in order to determine whether or not you have sampled enough of the enviroment to get an accurate look of that area’s richness. I’m not an expert, but I would imagine that a similar thing can be done with a specific species in order to tell how likely it is to be extinct
“A species is extinct when there is no reasonable doubt that the last remaining individual of that species has died.”
[Source](https://www.nationalgeographic.org/encyclopedia/endangered-species/)
We don’t know for sure. The Coelacanth is a fish that was declared extinct 66 million years ago but was rediscovered in 1938. Local fisherman knew of the fish earlier but didn’t know it was “extinct”.
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