The Oregon Zoo's 31-year-old polar bear Tasul was euthanized Friday due to an aggressive form of cancer.

Tasul was the third-oldest polar bear in any North American zoo or aquarium and one of the oldest in the world, according to the Oregon Zoo.

During an ultrasound last week, veterinarians discovered a mass on Tasul's right ovary. A biopsy determined it was cancerous and surgery was scheduled for Friday morning to remove the mass and determine whether it had spread.

During surgery, veterinarians said it became clear the cancer had spread extensively. The decision was made to euthanize Tasul to prevent her from suffering.

Tasul was just a few weeks shy of her 32nd birthday. Zoo workers said polar bears seldom live past 18 years in the Arctic, but biologists have documented two that lived to be 32.

Tasul was born Dec. 1, 1984, at the Riverbanks Zoo in Columbia, South Carolina and arrived in Portland in 1986.

In July, Tasul's twin brother Conrad was euthanized due to an untreatable liver tumor.

Tasul was supposed to serve as a friend and mentor to 1-year-old polar bear Nora. Nora arrived at the Oregon Zoo in September.

The two bears had met, but they had yet to become comfortable together, according to zoo keepers.

"One of the reasons Nora came here was to meet another bear," said curator Amy Cutting, who oversees the Oregon Zoo's marine life area. "It's beneficial for a young bear that was hand-raised to have a mentor bear as soon as possible, so we're in touch with the Species Survival Plan about what is best for Nora at this time."

Until a companion for Nora is found, Cutting said, the Oregon Zoo is fully prepared to provide care for her with enrichment, positive-reinforcement training and opportunities to participate in conservation science.

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