Are all mammals which managed to find their way into an environment...

Y

YoungPatriot

New member
...they're not native to considered introduce? Like rats. Rats have managed to colonize every continent in the world with the exception of Antartica. They've done this through man and their sheer brilliance, but man didn't intend to introduce them. They managed to find their way onto ship's and other means of transport, so what is this type of movement by animals called? Black rats, brown rats, and house mice colonising the world is quite similar to animals finding their way to a new land by rafts of vegetation. What do you guys think?
Sure, some of you might argue that if it weren't for humans travelling, then old world rats and mice wouldn't have found their way into the New world, but then again man didn't force rats into the new world, they got themselves there by stowing away on ships of man. So is the behaviour of these rodents considered natural? As natural as say bats colonising new islands or iguanas colonising islands via rafts of floating vegetation.
 
G

GC

New member
It relates to the time frame and whether humans have used technology to enable these species to become introduced. When introduction has occurred due to human activities it is regarded as unnatural. A raft of vegetation flows with the current, a ship goes against the current to specific destinations. Any species which travels with the ship could not reach that destination otherwise.

There are native rodents which have colonised regions in the ways you described, for example in Australia rats and bats are the only Eutherian mammals native to the continent. Bats flew there, rodents drifted or travelled across land bridges during the glacial maxima. They are now sufficiently diverse from the original populations in Asia to be regarded as unique species which makes them native (similar to the Dingo, a descendant of the Asian wolf brought by humans migrating into Australia from Asia around 4000 years ago).
 
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