Churchill is a remote frontier town that proudly calls itself the "Polar Bear Capital of the World."

The seaport is isolated -- you can't even get here by road. Visitors can arrive by plane, or train (when the railroad tracks aren't frozen over).

A panoramic view outside Churchill, Manitoba.

The polar bear's main source of food is seal meat, and the easiest way this land predator hunts them is when Hudson Bay freezes over.

The National Snow & Ice Data Center says seasonal ice in the southern-most region of the polar bear's habitat is already melting earlier and freezing later.

That means the polar bears are marooned on land longer, and getting hungrier.

"It's pretty common to see polar bears out here this time of year," said Steve Amstrup, chief scientist for Polar Bears International, a private group campaigning for the bear's conservation, when CBS News visited Churchill in November.

Currently, it's estimated there are between 20,000-25,000 polar bears in the wild. To many, that's a pretty sizable number. But what concerns Steve Amstrup the most are the bears in Manitoba who, he says, are experiencing the effects of climate change.

"They lose about a kilogram of body weight for every day they're on land," Amstrup said. "These guys are on land now a whole month longer than they were just 30 years ago."

The bears had started arriving in Churchill in July.

"We know that soon, all of the [polar bear] populations will have less sea ice than they do now," Amstrup said. "Some of them will have NO sea ice."

In November, while waiting for the sea ice, the bears lounge about, trying to conserve energy.

While they look as friendly as they are fuzzy, truth is they are one of nature's perfect killing machines. Their enormous size and strength are part of their allure.

A polar bear dawdles.

A hunting ground for nomadic Native tribes for several hundred years, Churchill was first settled by Europeans in 1717, with a log fort and trading post.

During World War II the United States Army Air Corps established Fort Churchill nearby.

As stated on Churchill's website, "the town comes alive each time the train or plane arrives."

With the annual arrival of polar bears, and the summer migration of beluga whales during calving season, ecotourism has become a major source of revenue for the town.

Of the town's 800 residents, more than half (56 percent) are Aboriginal (including Chipewyan, Swampy Cree, Métis and Inuit). While English is the main language, many of the Native residents speak Cree.

There are warning signs posted everywhere reminding the town's residents to be "Bear Aware," as they call it. One mother bear and her two cubs wandered up right behind the CBS News crew on a busy road just outside of town.

"I'd say it's safe to walk around Churchill in the day; I wouldn't say so at night," said Brett Wlock, a Manitoba conservation officer.

Brett Wlock's job is to keep polar bears away from people. If they can't scare nuisance bears away, they capture them, and bring them to what the locals call Polar Bear Jail. To make sure they're not tempted to come back to town again, the bears are given no food, just water, so that they do not grow accustomed to associating food with the town or its human inhabitants.

When their 30-day sentence is up, they're tranquilized and airlifted back out into the tundra.

A polar bear investigates the human riding aboard a "tundra buggy" -- a cross between a tour bus and a monster truck.

Polar bears generally walk at a speed of 3-4 mph, but are able to gallop as fast as a horse for short distances.

According to Polar Bears International, scientists believe most polar bears limit their range to a few hundred miles. However, one tagged female, tracked by satellite, traveled 3,000 miles between Alaska's Prudhoe Bay, Canada's Ellesmere Island and Greenland.

For more info:

Polar Bears International

International Polar Bear Day: February 27

Polar bears at Churchill, Manitoba (everythingchurchill.com)

By CBSNews.com senior producer David Morgan