Keo was 55 years old. He was the oldest living male chimpanzee in any North American zoo, and the first chimpanzee to live at Lincoln Park Zoo, a zoo news release said. He arrived in Chicago in 1959 when he was just 1 year old and fathered 11 offspring over the years, the release said.
"Keo was an incredibly special individual. He was truly a member of our family and will be missed dearly," said Curator of Primates Maureen Leahy. "His long, rich life is a testament to the wonderful care he received here as well as the veterinary advancements that have been made in the past five decades."
The median life expectancy for male chimpanzees living in zoos is 31.7 years. The maximum longevity record is 61 years, the release said.
The zoo says for the final years of his life, Keo lived predominantly behind the scenes at Regenstein Center for African Apes with two female chimpanzees, Vicky, and her daughter, Kibali.
"Keo was always full of personality, even as his health began to decline," said Director of the Lester E. Fisher Center for the Study and Conservation of Apes Steve Ross, Ph.D., who is the director of the Chimpanzee Species Survival Plan. "I can speak for everyone who knew Keo when I say his loss is felt keenly, and working with him was a privilege that we will all treasure forever."
A memorial page has been set up in Keo's honor, and Keo fans and friends of the zoo are welcome to leave comments, share memories, or express condolences to animal care staff who are especially affected by this loss. Visit the memorial page here: www.lpzoo.org/keo-memorial .