Has the trial introduction of penguins into the arctic & polar bears into the antarctic ever been considered . Since both maybe threatened species could it not be a way of expanding their range ? Any speculations on how they might ( or might not ) survive ?

With polar bears into the Antarctic the problem is the opposite of lack of survival. They would thrive and devastate the place. The other animals there have no adaptations to polar bear predation. The bear population would explode and kill off the penguins, and seals. At that stage, the bears would mostly die of starvation. The result would be dreadful all around.

Yes. Emporer penguin males spend three months over mid winter just standing in huge huddles incubating their eggs. To a polar bear, that's just an 'all you can eat' snack bar. It would mean rapid extinction to the penguins though.

Would there be a problem introducing some penguins in the arctic then?

 

If they don't go extinct in the first year after their introduction, and if they don't simply swim back to the antarctic, the only problem would be the competition with other fish eating animals (whales, seals and other fish... and us humans).

You mean, take the penguins to the polar bears instead of taking the polar bears to the penguins?

 

Well, they are smaller, so it would be easier I suppose...