CALGARY -- Their black and white coats are built to withstand the cold, but many of the Calgary Zoo's penguins have been moved inside because of the bone-chilling weather.

Zoo curator Malu Celli said the king penguins have been brought in from their outdoor enclosure on several days during Calgary's latest cold snap.

Zookeepers follow a guideline that if temperatures fall below -25 C, it's safer to keep the penguins indoors, said Celli. Temperatures have averaged -28 C in recent days, she said, and with the wind chill, it can feel more like -40 C.

"We just don't want to expose them to too much," Celli said Sunday in an interview. "To keep them safe, we decided to pick a limit to let them out."

Celli said the zoo has 51 penguins in its flock, representing several species from a range of habitats.

King penguins are often found in the subantarctic region, she said, so they are accustomed to chilly weather, but tend to live in milder climates than their Antarctic-dwelling cousins, emperor penguins.

At the Calgary Zoo, king penguins spend their winters waddling in open air, Celli said, but every year, Calgary's frigid temperatures force them to temporarily return indoors.

"It's not necessarily that it's too cold for them," she said. "I believe that physiologically, they can withstand colder weather than what we have here, but these are not wild birds."

The tuxedoed birds would happily go outside if they could, she said, but with a chick in the flock who is still maturing, zookeepers prefer to err on the side of caution.

"It's kind of like you can bundle up your kid, but then there's a point you're going to say, 'I know you're good, but I'd rather you stay inside now,"' said Celli.

Celli said zookeepers have made adjustments for several exhibits on account of the cold, and humans are still welcome to check out the park's attractions.

"If you are brave and you come to the zoo, you're pretty much going to get the zoo all to yourself," she said.