Like, I imagine introducing a pregnant crocodile to an English river. I get that it’s colder than it’s natural climate, but what’s it gonna do? Freeze to death?
Climate etc. explains way less than I want it to.
My question is a mix of ‘Why CAN’T an animal exist somewhere?” and “Why HASN’T someone introduced it?”
In: Earth Science
Well let’s follow your pregnant crocodile in this English river. She is alone in an unfamiliar environment with many new challenges. Let’s say she survives the cold and manages to adapt well enough to find food and stay out of danger (including humans who would remove or kill it if they noticed it was there). This by itself would be a great challenge, especially once the baby was born and required extra care.
So now you have a mother and a baby (lets say he happened to be born male) and the baby survives to adulthood. He now seeks out a mating partner, fruitlessly. His mother is too old or dead and he may never stumble upon her again anyway. Then the male crocodile eventually dies and that’s that. No crocodiles populating the English river.
Introducing a pregnant crocodile would be as if I dropped you in the desert. There are people living in deserts, so technically you should be able to survive it, but you’re not used to the weather circumstances, neither do you have the right survival techniques. For the crocodile goes the same thing. Technically the English river is water and it has fish in it. But it is not physically adapted to the circumstances there, so it wouldn’t survive.
Also, many animals have just gone extinct in certain areas of the world because of people. We either take away their habitat, or we take away the animal itself. For example, there used to be lions around the Mediterranean, but because the Roman empire used them in their arenas, they went extinct. We can’t reintroduce them there anymore because there are too many cities now: it would be dangerous both for them and for us.
A lot of animals need very specific living conditions.
A crocodile would most likely freeze to death in England. Also the crocodile probably would have a hard time finding food since there are no big prey compared to in Africa where you have stuff like wilderbeast and zebras. Also, the bigger animals living in england, like deer, are not as reliant on rivers to get water unlike in Africa where water is scarce. This means that the crocodiles hunting method of simply lying in the river until a big animal stops to drink won’t work.
Introducing animals to new locations is also very difficult to do in a good way. Most ecosystems are in a very delicate balance and introducing a new animal which does not have any competition/predators will quickly explode in numbers and can off set the balance completely, destroying the ecosystem and leading to the species there originally go extinct.
Because of this reason you are not allowed to release animals anywhere you want or introduce new animals to new areas. This is also the reason why Austrailia for example have so tough border controls to make sure people don’t bring in animals or seeds or plants to their unique and delicate ecosystem.
Austrailia has some of the worlds most unique animals which are extremely sensitive to changes in their environment. So even a seemingly harmless new animal could easily kill off entire species.
For can’t, it’s easy, some just don’t have the biological prerequisites to live there. Many animals have specific diets and abilities that environments won’t entertain. Maybe they’re unable to handle really hot temperatures or long periods without water. Maybe they eat a specific plant and won’t survive without it.
This doesn’t apply to everything of course, many just simply don’t have the motility to travel, for whatever reason, and therefore just haven’t traveled. When some do, they flourish, because they can tolerate the environment and food, but also have no natural predators to keep them at bay. That leads into why people HAVEN’T.
Invasive species generally will be exterminated whenever they can, because they do just as implied, invade. They don’t have anything to keep them in check, so they just eat away and kill everything, while booming. It can entirely change the ecosystem in an area. An example of this is an invasive crab species that might eat all of a certain type of fish in an area. This can cause total havoc in the ecosystem and lead to a collapse of what we know. The world will survive, but with less diversity and potentially huge human impacts.
While all ecosystems are connected, they’re separated. Introduction of a new predator, or even a new bottom level organism with no predator can result in crazy population booms that destroy it.
Either it can live somewhere else and it spreads like wildfire or it doesn’t last and dies off.
People have done, through-out history. Like, a lot of things. Your question stems from lack of knowledge other than from it not have happened.
We have quarantine laws for reasons.
Niches. An “introduced” animal has to compete for food with all the species that are already there and usually have been adapting to that exact environment for millions of years. And the ecosystem has adapted to them, meaning that there’s only so much food to go round for existing foodchains to be sustainable.
Sometimes the newcomer has an edge and successfully claims the niche, but that only means the native species are the ones driven to extinction.
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