Why aren’t there polar bears in Antarctica?



The Arctic and Antarctica, whereas comparable habitats in some methods, are house to very completely different creatures. Each poles host quite a lot of seal and whale species, however solely the Arctic is house to Earth’s largest bear, the polar bear.

Polar bears (Ursus maritimus) and their tumbly cubs may be found around the Arctic Circle in Alaska, Canada, Greenland (a part of Denmark), Norway, Russia and, often, Iceland. A polar bear’s fur is specifically suited to temperatures that may dip under minus 22 degrees Fahrenheit (minus 30 levels Celsius). They dwell on ice for many of their lives, feeding on fat-rich seals that maintain them energized for lengthy intervals between meals.

Antarctica additionally has sea ice, chilly temperatures and seals. So why aren’t there any polar bears on the southernmost continent?

The reply has to do with evolution and the geologic historical past of Earth.

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Bears are largely a Northern Hemisphere phenomenon,” mentioned Andrew Derocher, a professor of organic sciences on the College of Alberta in Canada who has studied polar bears for almost 40 years. Other than the Andean bear (Tremarctos ornatus) of South America, bears seem solely within the Northern Hemisphere. There is no particular motive for this, simply that some species evolve in some locations and a few do not. “Biogeography is stuffed with oddities,” Derocher mentioned. “Some species made it to new locations and a few did not.”

For polar bears particularly, there was by no means a time of their evolutionary historical past when the North and South poles had been linked by ice (or land, for that matter). Folks say polar bears are the “greatest terrestrial carnivore on this planet, and but they are not a terrestrial species in any respect,” Derocher advised Reside Science. The large, white bears dwell on sea ice for nearly their total lives, solely often coming ashore to breed.

Polar bears are, evolutionarily, a comparatively younger species. They developed from a typical ancestor of the brown bear (Ursus arctos) someday between 5 million and 500,000 years in the past, Derocher mentioned. However even 5 million years in the past, the continents had been in comparable positions to the place they’re in the present day, so polar bears by no means obtained the chance to journey from pole to pole. The closest landmass to Antarctica is the southern tip of South America, which incorporates Chile and Argentina. To get to Antarctica, polar bears must cross the treacherous Drake Passage. The world can be identified for powerful storms and rough seas as chilly water from the south runs into heat water from the north.

But when polar bears obtained the chance, would they survive on the South Pole?

To Derocher, the reply is easy: “They’d have a lot enjoyable in Antarctica.”

Within the Arctic, polar bears feed on seals and the occasional hen or egg. Antarctica is plentiful in all three, with six seal species and five penguin species. Plus, none of these animals have developed to be cautious of enormous, land-roving predators. The Antarctic panorama can be a free-for-all buffet for a polar bear — which is why nobody ought to ever deliver polar bears there. Their voracious urge for food, mixed with the native faunas’ ignorance of enormous land predators, would seemingly result in ecological collapse. It is in all probability finest for the nice white bear to stay within the north.

Initially printed on Reside Science.

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