South Polar Bears

Question

The Arctic ice cap is melting away soon. Some (probably misguided) ecoactivists think it would be a good idea to safeguard certain indigenous species of the North Polar region (especially mammals) by migrating them to the opposite side of Earth: Antarctica.

Let’s assume they have the necessary financial and organizational means for such an endeavor. They are willing to accept some losses of native wildlife and changes to the Southern ecosystem, but not the extinction of a whole species. They’re aiming for a self-sustaining habitat, i.e. without humans hunting down predators, feeding and nurturing potential prey, nor fencing off protected areas.

How can I reasonably and believably estimate for my activists …

1. Which species could be transferred without too much probable harm to themselves and others (e.g. polar bears eating all the penguins)?
2. How many individuals of each should be relocated?
3. When during the year which species should be moved (since it’s the opposite season in the other hemisphere)?

Answer 1

My answer is that history has shown us that this isn't possible without disaster for the ecosystem. So many times there has been attempts at introducing new species for various reasons and I cannot think of one instance where this has not gone haywire in one way or another. Sometimes in ways you wouldn't expect.

So the polar bears might eat the emperor penguins as the males gather to protect the eggs through the long winter, but there might be other consequences. Maybe the polar bears have parasites or viruses that are harmless to the polar bears but devestating to the native population of seals. Maybe the conditions of the snow down south make it difficult for pregnant polar bears to find proper shelther throughout the winter to give birth.

The same difficulties would repeat with all other species. Even through the antartic is cold in a similar way to the artic it is also a very different place. Would newly introduced species know how to find food? Would they be able to function without access to a mainland with vegetation and mammals?

There is simply no noninvasive way to do this. Any land set aside for new species would encroach upon the area of native species that already walk a knives edge of survival.

It would be a lot easier to build something in northern Canada or Russia.

Answer 2

Polar bears eat ice seals (and some others). Could they learn to eat Antarctic seals instead? Maybe. Would they eat penguins? Maybe. In both cases, the hunting for them would be different, as the habitat isn't the same and the prey animals have different habits.

This would change the balance of seals (or penguins) and affect their prey. And their other predators would have less food.

Can you bring down the Arctic ice seals and other seals? Sure. But then they would compete for food with the existing seals (assuming the food was close enough to Arctic food for them to make the transition).

This changes the fish and mollusks and sea vegetables and plankton and pretty much everything. How does the forced migration change the gut biome of the polar bears? And of the other Arctic animals. Will their droppings change the formation or growth of the microscopic organisms and other small lifeforms that various Antarctic animals depend on?

So the answer to your first question is: none. I'm trying to think of any transplanted species that thrived but did not cause vast changes to the existing ecosystem. Even bees and earthworms have done this in the Americas. Not all change is bad for the ecosystem as a whole, but it will harm (or even wipe out) some species.

As to your second question... Polar bears are solitary and don't live in groups, so the numbers you need would be for reproduction. Anything up to 20-25K (which is the estimated total wild polar bear population). There are 15 groups of polar bear populations, which leads me to believe that 1000 polar bears would be a reasonable relocation group size. Most polar bear litters are 2 cubs and a female has about 1 litter every 3 years. The smallest home range area for a group appears to be 50K square kilometers.

I don't know the answer to your third question, but I would guess that a good time would be after they've done some heavy feeding in preparation for winter.

Sources: There is lots of similar info in many places over the internet. Some good basic facts are here: https://seaworld.org/animal-info/animal-infobooks/polar-bears/habitat-and-distribution