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What is the term for an event in which a species is still alive, but has no chance of future reproduction and the species will be considered extinct once the current generation dies out?

For example a species of a tiger that has the last 5 surviving members left and which are all related and all male. Hence, even though they are still alive, there is no chance that the species will be able continue their bloodline and hence are already "technically" extinct.

Pringles
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This is technically called Functional extinction. With no viable reproducing population the species will almost certainly become extinct. Note that humans could potentially mess with this through the use of reproductive technologies.

Harry Vervet
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  • Are humans functionally extinct? It is all but certain the species will become extinct. Probably long before the sun dies. But even if the humans figure out how to migrate to another solar system, that is just putting off the inevitable. – emory Jan 08 '16 at 20:03
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    @emory All species were created at some point in time, and all become extinct eventually, whether that be hundreds, millions, billions of years into the future. Humans are not functionally extinct, at least not by any useful definition of the term. – Harry Vervet Jan 08 '16 at 20:20
  • Functional extinction is a bit more broadly defined. I don't know if it accurately describes the last living individuals of a species past the tipping point, but it's still a good answer (upvoted). – anongoodnurse Jan 09 '16 at 00:09
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For this matter, I'll call it Ecological Extinction. That means you still have an extant population, but the individuals in which you are focusing on do not interact any longer with their surroundings and environment as they should. For ex., they're no longer preying or being predators, they no longer reproduce because effective population (Ne) isn't enough. There's an example in which you can make some research on, and it's about the Ecological Extinction of Nomascus leucogenys (white cheeked gibbon) in Yunnan Province, China. There are some papers about it, which you'll easily find if you go to Google Scholar. Hope I helped.