PORTLAND – Veterinarians at the Oregon Zoo euthanized a 17-year-old, geriatric Amur leopard Tuesday, because they said he had been suffering from an aggressive form of terminal cancer.

Fred, the Amur Leopard, roams his yard in the Oregon Zoo.

Veterinarians and zookeepers were by Fred’s side when he died and staff members said they were deeply saddened by his passing.

"We had a lot of people involved in managing Fred's care," said Chris Pfefferkorn, general curator. "It became apparent that his quality of life was not improving, despite the best efforts of all involved. Zoo veterinarians and staff determined that the only humane thing to do was to euthanize him."

In September, zoo veterinarians performed surgery on Fred and discovered a tumor, which they immediately removed. Chemotherapy was begun to try to eradicate the cancer. However, during his third dose, veterinarians discovered the tumors had reappeared.

"Losing Fred is extremely difficult for everyone involved in his care. He was a very special cat and a wonderful ambassador for his critically endangered species. He will be sorely missed,” Pfefferkorn said.

A post-mortem examination, known as a necropsy, will be conducted on Fred, to help with research.

"Fred could help improve the understanding of cancer in leopards," said Pfefferkorn. "Studying his remains can provide important insight. Through a comprehensive necropsy, we hope to discover clues on how we can improve the health and welfare of the world's few remaining Amur leopards."

Fred came to Portland in April 2000 from the Cheyenne Mountain Zoo in Colorado Springs, Colo. His arrival was considered a first step in returning big cats to the Oregon Zoo after major exhibit construction had necessitated removal of the old feline building.

Kia, a 12-year-old female Amur leopard who shared Fred's exhibit space, remains at the zoo. She and Fred were not a breeding pair. Kia came to Portland last year to help create more breeding space at her former home, the Erie Zoo in Pennsylvania.

Amur leopards have a life expectancy of about 15 to 19 years in captivity. Native to eastern Russia, they are considered critically endangered, with only about 35 to 45 of the animals left in the wild.

Also known as the Manchurian or Korean leopard, the species has slowly drifted from Korea, its original habitat, to China and finally to eastern Russia, where zoologists say it is making a last stand. Its habitat today is mainly the mountains along Siberia's Amur River Valley, where habitat destruction and loss of prey species have greatly reduced its numbers.

Amur leopards are mostly nocturnal and are "opportunistic" hunters, taking whatever kind of prey they can handle. Deer and boars are major food favorites. Adult leopards usually weigh 75 to 100 pounds and stand about 3 feet high. Like their African cousins, Amur leopards have tawny coats spotted with many widely spaced, thick-bordered rosettes. The Russian leopards, however, have a more intense coloring and longer fur, allowing them to survive in cold and snowy areas.