PORTLAND, Ore. — Oregon Zoo polar bear Tasul was euthanized Friday to prevent suffering due to an aggressive cancer, according to Oregon Zoo officials.

"A couple weeks shy of her 32nd birthday, Tasul was the third-oldest polar bear in any North American zoo or aquarium, and one of the oldest on the planet," said zoo spokesman Hova Najarian. "In the Arctic, polar bears seldom live past the age of 18, though wildlife biologists have documented two that lived to be 32."

Zoo veterinarians discovered a mass on Tasul’s right ovary during an ultrasound last week. A biopsy revealed it was cancerous and surgery was scheduled for Friday morning to remove the mass.

"During surgery, however, it became clear the cancer had spread extensively and, to prevent her from suffering, animal-care staff made the difficult decision to euthanize," Najarian said.

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

"Keepers are disappointed that Tasul will not have the chance to serve as a friend and mentor to the 1-year-old Nora, who arrived here from the Columbus Zoo this fall," Najarian said. "While the two bears had met, they had yet to become comfortable together."

The zoo's senior marine life keeper, Nicole Nicassio-Hiskey, knew Tasul for more than 15 years.

“We know many zoo visitors are grieving along with us right now,” she said. “Tasul touched a lot of people’s hearts, and she was such a great bear. She helped raise awareness about what’s happening to polar bears in the Arctic, and she helped the scientists who are studying what’s happening there. Wild polar bears are in trouble, and their future depends on all of us working together to combat climate change.”