Denver Zoo Steps in as Surrogate Mother to Orphaned Polar Bear Cubs : Wildlife: Veterinary staff takes over when pair are abandoned soon after birth. If they reach adulthood, they will be the first since 1982 to be successfully raised by humans to adulthood in a U.S. facility.

Klondike squealed and flapped his furry arms and legs in the air when Denver Zoo vet Dr. David Kenny rolled the baby polar bear on his back.

Like human babies, Kenny explained, polar bear cubs can’t easily turn themselves over. “They’re pretty undeveloped compared to most carnivores.”

Born Nov. 6, Klondike and his sister, Snow, were abandoned by their mother, Ulu, soon after their births. A keeper spotted them lying on the cold, damp floor of the Northern Shores exhibit.

They are the first polar bears born at the zoo since 1977. If they reach adulthood, they will be the first to be successfully raised by humans to adulthood in a U.S. zoo since 1982.

They are a demanding pair, often screaming in high-pitched tones to be fed. They also take long naps on slabs of ice.

Both are covered with white fuzz and have opened their big brown eyes. They have grown from just over 1 pound at birth to around 15 pounds. Their paws are big, and they’ll get much bigger. Adult polar bears like their father, Olaf, weigh around 1,000 pounds and have been known to break a human’s neck with one blow.

Little is known about polar bear infancy in the arctic, so the caretakers of Klondike and Snow are learning as they go.

“We’ve even had polar bear biologists call up and ask if they had hair,” Kenny said. “They didn’t know. . . . They’d never seen them.”

Kenny said Ulu was a first-time mother who didn’t show signs of pregnancy but seemed nervous. Polar bear mothers must feel secure during gestation, which Kenny said is difficult to duplicate in a zoo exhibit.

“A wild female polar bear would find a snowbank, burrow into it, have the babies in a cave where it’s dark, secure, with no bears around, no people around--and the bears would stay in there until March or April,” he said.

In 1982, the San Francisco Zoo chose to raise Pika, a female born to a mother with a history of babies who died young.

“Our polar bear breeding program was going down the tubes,” said Mike Sulak, curator of the San Francisco Zoo, “so we elected to hand-raise her.”

At Zoo Atlanta that year, zookeepers were raising Andy Bear. Coincidentally, Andy Bear and Pika now live together in San Francisco.

Sulak said hand-raising polar bears means “moving your hands fast,” to avoid tiny sharp teeth. It also means providing a sterile environment in the beginning.

“Up in the Far North, in the cave, it’s all frozen, and basically it’s bacteria-free,” Sulak said. Polar bears are native to Northern climates from Alaska to Labrador, as well as Denmark, Norway and Russia.

The whelping pen is kept at a cool 65 degrees to avoid heat stress.

“If it’s above 70, they start panting,” Kenny said.

Klondike and Snow are bottle-fed at four-hour intervals with a mix of distilled water, half-milk and half-cream, safflower oil and vitamins.

“Trying to come up with a diet is not easy,” Kenny said, “because the fat content in polar bear milk is higher than a whale, and that’s unusual for a mammal.”