The Oregon Zoo is celebrating its successful polar bear program with birthday cake for two of the resident bears.

Oregon Zoo photo

Conrad, as a small cub, gives his mom a kiss, as Tasul waits her turn. Photo by Tony Vecchio, circa 1985.

Conrad and Tasul were born in the Riverbanks Zoo in Columbia, S.C. 23 years ago and then were later moved to Oregon.

In the early 1980s, polar bear cubs born in zoos rarely survived. But Conrad and Tasul have done well since their birth in 1984.

Tony Vecchio, now the Oregon Zoo's director, also used to be zookeeper for the bear cubs.

He’s leading a celebration at the zoo Dec.

28, at 10 a.m. The zoo's other polar bear, 22-year-old Yugyan, will also be honored.

“All three birthday bears will receive presents, a dusting of snow, igloos, snow treats and ice cakes made by the zoo's executive chef, Paul Warner. Zoo visitors are invited to join the party and enjoy cupcakes from Haggen Food and Pharmacy,” said zoo marketing director Bill LaMarche.

"This birthday party is special in that I've known Conrad and Tasul since they were born," added Tony Vecchio, zoo director. "We hope we can spark an emotional connection with polar bears in our visitors too. Conrad, Tasul and Yugyan help tell the story of what's happening to their relatives in the wild."

Thinking back, Vecchio described why Conrad and Tasul's birth was unusual.

"The mother-cub relationship is critical," he said. "At birth, the cubs are bald and weigh one pound. The mother is everything to them, even after three months, when they emerge from their snow den in the wild. At that point, the cubs weigh 30 pounds and the mother could be down to half her weight. Before 1984, breeding programs were unsuccessful. For this birth, we gave the mother extra quiet and privacy, in an environment where she felt safe and stress-free. That hadn't been done before. So these are very special bears."

The primary threat to wild polar bears is climate change. The sea ice is arriving later each season and melting sooner, which means the bears must swim farther every year to find food.

The World Conservation Union's Species Survival Commission has recommended that the polar bear be reclassified as a vulnerable species, and has placed it on its Red List, which identifies species facing a high risk of global extinction.

Conservation groups are also urging legislators to classify polar bears as threatened under the U.S. Endangered Species Act, to further protect the bears from the consequences of global climate change and other threats.