How are scientists able to say that a random species is extinct? Did they have to look everywhere?

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How are scientists able to say that a random species is extinct? Did they have to look everywhere?

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Its more they check for long enough and find nothing.

The fact that we know about them in the first place, and can track declining numbers for some, makes their absence the basis for that decision.

That said, some species turn into hide and seek champions, showing up long after they are “presumed extinct”

They can refer to the species as “extinct” when no living members of the species are known to remain anywhere. That doesn’t mean the species actually and truly is extinct, it just means that there is no available evidence to provide that it is not. Sometimes that’s easy – for example, large land-based animals like rhinos are easy to spot and count – and sometimes that’s hard because the creature is small such as an insect, or widespread, or living in a still-very-wild area.

Sometimes species that were thought to be extinct are rediscovered later on. Probably the best known example is the coelacanth, a large fish from the time of the dinosaurs that we found in the fossil record. It was thought to have been wiped out when the dinosaurs left… until they caught one in the 1930’s. Crazy looking fish too.

Others have their last remaining members captured and moved to zoos. Tasmanian wolves are an example here, there’s black-and-white footage of the last known one in captivity before the species was lost.

To complement other answers, pandas have been declared extinct because no one found any for a century.

It’s not that complicated. It means we can’t find them anymore.

They know that certain animal lives in certain areas and when they are unable to find any after some time. They will declare them as extinct.

As you might imagine it’s easier to find some animals than others, which means we got it wrong from time to time.

Luckily it’s very easy to prove, when they were wrong. If you find any members of the species than they are not extinct.

Usually they get declared extinct after no one has seen one in a while.

For example the Bramble Cay mosaic-tailed rat was a small rodent only found on the small Bramble Cay island.

The island isn’t big and the last time anyone saw any of them was in 2009. since then people have gone looking for survivors several times over the years until in 2019 the Australian government and the ICUN in 2015 labeled them as ‘extinct’.

There is a chance that some of the small rodents might still live somewhere but unless on is found they are considered to be extinct.

They don’t have to look everywhere. They only have to look in the places you’d expect to find it. Dodos were only found on Mauritius so they didn’t have to look in Belgium to see if one turned up there.

Of course if the animal has a wide range it can be hard to tell. Usually they’ll wait a while before declaring it extinct.

Sometimes they’re wrong and it’s still around but that’s no big deal.

Nowadays, we tend to closely observe animals that are close to extinction. Scientists will tag and keep watch of them and generally have a good idea of how many remain. If and when one dies, they tend to know. If they’re aware of the total population and they’ve been observing for decades and watching them die off one by one, they can say with confidence that they are extinct.

For animals that aren’t as closely observed or perhaps live in a larger geographical range, if no animals of this species have been seen in the area for a certain amount of time, they’re classified as extinct.

But if they somehow, miraculously, reappear, they can be moved from extinct to not extinct.

The Okapi was once considered extinct (and I believe was used on the logo of a charity/organisation for extinct animals? May be remembering that wrong) but was later rediscovered.

The most famous example though is the coelacanth. So species absolutely can be declared extinct and slip under the radar.

Also there’s a lot of reports of some extinct species, like the Thylacine, being sighted from time to time.

All science is always “to the best of our knowledge”.

A species can be declared extinct when it isn’t found anywhere for a long enough time that, to the best of our knowledge, it appears to have died off entirely.

Sometimes we’re wrong and we find that species again later! But science is always able to be proven wrong; that’s how we learn.

They can’t

It’s literally speculation based on not having seen the said species in its known habitat

Of course, the species could have evolved super intelligence and is now living in an underwater city called Rapture far from human eyes

But most likely lack of sightings means they’re either gone or very few remaining

Scientists are actually proven wrong from time to time when they think a species is extinct only to find some tiny pocket of the planet in which it still exists.

They check not only for the animals, but for feces, bones, and other traces and pieces of evidence that the animal is known to leave behind. They also monitor reports by people living in near the habitat to see whether there are any sightings, as well as populations of known prey.

Cannot look everywhere for obvious reasons. They have to do a statistical evaluation. At some point, the odds of the thing still existing when never seen despite being sought in all the places it likes to live, does lead to a pretty good likelihood that the poor lifeform is no longer in existence. And yet, there is an occasional find of something thought to be extinct for quite some time.

Scientists and hobbyists in many places around the world track and report populations of animals. For example, you can track the population of local birds in the US through apps on your phone.

Eventually people stop reporting sightings of a specific plant or animal and they are considered extinct after enough time has gone by. The system isn’t perfect and some animals do reappear, but for the most part once an animal is extinct it is really gone

It’s pretty easy to guess these days because while we can’t track each individual animal, it’s pretty easy to track the loss of their habitats, which is the real driver of extinction. If the forest is gone, the critter that lived in it is likely gone with it.

It’s impossible to prove a negative. So we assume it’s true until proven otherwise. That is, we assume a species is extinct so long as we have no proof otherwise.

So if we found a species, but all the ones we were tracking died, we will assume it’s extinct until we find a new one.

Like all of science, we have to assume the universe is how we perceive it until proven otherwise.

When it comes to declaring a negative (that something is not true, does not exist, no longer exists, etc) most scientific conclusions are about looking long and in depth enough to say with confidence that we’ve investigated every reasonable possibility and can draw the conclusion that it is *overwhelmingly likely* that things are the way we’re concluding.

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Confirming the positive is a lot easier. You know you’re 100% correct the first time you see a giraffe that giraffes are not currently extinct. Not finding a giraffe doesn’t mean you can confidently say it’s extinct just on its own, but eventually when you look long and thoroughly enough to say you’ve checked every place a giraffe could plausibly survive and found no evidence of one, you can say giraffes are likely enough to be extinct that you can treat it as they are.

What a good question. Love this. Check out the [Coelacanth](https://en.wikipedia.org/wiki/Coelacanth) discovery.

Short answer is no they don’t. It’s an assumption made when they can’t find evidence of modern encounters.

“Extinct” species are occasionally rediscovered in the wild. There’s also the long-standing issue that the distinction of what constitutes a “species” is more or less arbitrary.

e.g. historically one of the main tests for a “species” is genetic isolation, but to make the example gene-flow between domesticated dogs, Coyotes, and Wolves is quite free to the point that almost all wild coyotes/wolves have some mixed fraction of ancestry between the two species. Morphological distinctions to define species are also arbitrarily applied, to use the dog example again, the gap between a Labrador and a French Bulldog is bigger than many species gaps.

Evidence of absence is evidence. If we know a species makes nests in certain areas and they don’t anymore, then we don’t find the species there anymore. The lack of evidence for it’s continued existence is a type of evidence that helps form our conclusions.

Like if the police want to make sure nobody is in a house, they may stake it out. If nobody comes and goes from the house for a few weeks, they can be reasonably confident that the lack of evidence suggesting a presence means there isn’t a presence.

Of course, should a species be rediscovered because it was forced to relocate deep into say, the rainforest, it’s status would simply change when we got that new information proving they aren’t all gone.

Extinct isn’t so much a declaration of what is, as much as what we can currently find. Extinct means, “We done looked and didn’t see hide nor hair of it. Fuck knows.”