Kutai, a 20-year-old Sumatran orangutan known for his intelligence, creativity and fun-loving personality, died Saturday at the Oregon Zoo following a monthlong illness, officials said.

"It's a devastating loss for everyone here," said Mitch Finnegan, the zoo's lead veterinarian. "Our animal-care staff did all we could for Kutai, but we just couldn't help him through this."

"He was one of those animals with a strong presence and a big personality. It's hard to imagine the zoo without him."

—Mitch Finnegan, lead veterinarian

Dr. Finnegan said the zoo's animal-care staff had been treating Kutai for an ongoing medical issue since early last month, and that he had been responding well. Yesterday morning, though, the beloved orang's condition declined greatly, and he died in the afternoon following a minor surgery.

Zoo staff had great affection for Kutai, describing him as extremely intelligent and creative. Before Red Ape Reserve opened at the zoo in 2010, keepers joked that they needed to make the habitat "Kutai-proof," referring to the orang's love for dismantling objects, which he often fashioned into his own toys and tools.

"Kutai was the 'engineer' in the zoo family," said zoo director Kim Smith. "If anyone could take something apart, he could. He was mischievous, but sweet and fun-loving at the same time."

Kutai was born Dec. 16, 1993, at Sedgwick County Zoo in Wichita, Kan., and came to Portland in 2001. He is survived by his grandmother, Inji, who at 54 is the oldest Oregon Zoo resident and one of the oldest orangs anywhere. According to the Association of Zoos and Aquariums, the median life expectancy for Sumatran orangutans is 25.1 years for males and 32 years for females, though they sometimes can live up to 60 years.

"I remember very well when Kutai first arrived here," Dr. Finnegan said. "He was this goofy, gangly 8-year-old adolescent, and we watched him grow into a huge, burly full-grown orangutan. He was one of those animals with a strong presence and a big personality. It's hard to imagine the zoo without him."

In December, keepers reported a decline in Kutai's appetite and activity, and a veterinary exam revealed a very high white-cell count, which can be a sign of an infection. He was treated with antibiotics and showed great improvement; meanwhile veterinarians tried to identify the source of his problem, suspecting airsacculitis.

"Orangutans have inflatable air sacs along the sides of the neck, which can be prone to infection," Finnegan said. "We scoped those in Kutai and found there were openings between one of the air sacs and his trachea. At that point, we thought he had pneumonia."

Surgery was performed on Thursday, Jan. 2, to close the openings, and initially at least it seemed to help. Animal-care staff reported that Kutai looked much improved afterward and had a good appetite, eating all of his food that evening. The following day though, he had become lethargic once again, and by Saturday blood work showed him to be severely anemic, necessitating a second surgery. Unfortunately, Kutai did not rebound a second time and died post-surgery upon returning to the zoo's primate area.

Following standard zoo protocol, Finnegan and other animal-care staff performed a necropsy (animal autopsy) on Saturday evening, which they hope will eventually help determine the cause of Kutai's abrupt decline. Tissue samples are being submitted to a pathologist for analysis.

"We know many visitors are grieving along with us right now," said Asaba Mukobi, the zoo's senior primate keeper. "Kutai touched a lot of people's hearts, and he helped raise awareness about what's happening to orangutans in in their native lands."

Habitat loss, palm oil plantations and an illegal pet trade are pushing orangutans toward extinction in Sumatra and Borneo, and, according to Orangutan Outreach, it could be fewer than 10 years before they have completely vanished from the wild.