How do they know an animal is for sure extinct?

Question

How do they know an animal is for sure extinct?

Answer 1

They don't! Lots of "extinct" animals and plants have been spotted years after they were believed to have completely died out. For example:

http://news.bbc.co.uk/1/hi/sci/tech/4493...

Answer 2

That is one of the difficulties with declaring an animal 'extinct'.

For example, the ivory billed woodpecker was considered extinct for many decades, but just a few years ago some trained naturalists were pretty sure they spotted one. Now an intensive hunt is on to see if they really have survived or not.

There have even been cases where an organism thought to have been extinct for millions of years turns out not to be extinct.

The most famous example is the coelacanth. It doesn't quite count, because in that case, it wasn't that the species was thought to be extinct - that particular species was completely unknown - but the lineage of fish that the coelacanth was in was thought to be extinct. As it turned out, there was an odd member of the group (the coelacanth) that survived deep down in the ocean - far from the typical habitat of earlier coelacanth brethren. As it turned out, the coelacanth wasn't unknown to fishermen of the area (or in Indonesia, where more coelacanth turned up, unknown to science until a decade ago). The fishermen knew about the fish, but didn't know there was anything scientifically remarkable about it. They just didn't bother with it because it tastes gross.

Another example was the metasequoia, a type of tree that had been thought to be extinct since dinosaur times. Then they found some growing in a remote Tibetan monastery. Of course, the monks knew it was there, they just didn't know that scientists would find the tree remarkable. They just thought it was a tree.

In the case of critters like the Loch Ness monster, it is not in a very isolated environment. It's in a place that has been inhabited by people for thousands of years, with no reliable sightings in all that time. It's been searched by scientists. And the geology of the area is incompatible with it having remained untouched for millions of years.

While places like the depths of the oceans, deep tropical rain-forests, remote dismal swamps and the like may yet hold out opportunities to find new, large species, or reveal species that were long thought extinct elsewhere, it is highly unlikely that Loch Ness is one of those places.

Answer 3

poke the bones with a stick and see if they start to move lol

Answer 4

Usually if no one has seen an animal alive in the last 50 years, it is considered extinct.  Some animals proclaimed extinct are later rediscovered.  

Answer 5

That is a very good and interesting question I suppose they dont for sure.

Answer 6

They don't know for sure. They base this on the information they have gathered over the years. Some animals have been classified as extinct and decades later they are seen.

Answer 7

Perform a prolonged survey at their former habitat.  If you know what you're looking for and spend enough time at it, then you've got reason to suppose the critter is probably extinct.  If subsequent surveys achieve the same result, you've got an even better reason.

However, on occasions you may turn out to be wrong.  Perhaps there are several left.  Revise your assessment to almost extinct.  Perhaps there are quite a few of them somewhere you didn't check.  That might lead you to revise the status again; perhaps to endangered.  Should you find your initial assumption was wrong, then that's actually good news.

Unfortunately, it's normally not wrong.

Answer 8

actually they don't they say it when people don't see them anymore living but some can still exist.

Answer 9

it is almost impossible to tell but t rex  it positively gone but in the congo there have ben sightings of certain dinos and pterasuars in the amozan theres been sightings of the giant ground sloth new zeland moa sightings have surfaced australia megalania has been seen nessie and champ sighting and a ton more you could say dinos are with us still so you really cant be positive if there extinct or not

email me if you want a list of supposed exinct animals  

Answer 10

If you no longer see them alive anywhere.