Remembering Keo

The Lincoln Park Zoo family is sad to bid farewell to one of our oldest friends. Chimpanzee Keo, the oldest male chimpanzee in a North American zoo at 55, was humanely euthanized today.

As everyone who’s bonded with animals knows, this is never an easy decision. But our animal care staff always puts animal needs first. Advanced cardiac disease had irreversibly compromised the quality of Keo’s life. And so it was time to say goodbye.

Keo came to the zoo as a baby in 1959. His energy and personality thrilled generations of zoogoers as he grew to be one of the zoo’s icons.

Chimpanzee Keo was a longtime--and beloved--Lincoln Park Zoo resident

Chimpanzee Keo was a longtime--and beloved--Lincoln Park Zoo resident.

In recent years the geriatric male had lived mostly behind the scenes at Regenstein Center for African Apes, in a social group with female chimpanzees Vicky and Kibali. But he still had a memorable impact on the caregivers who interacted with him daily, impressing them with his continued curiosity. Even as Keo celebrated his 55th birthday this summer, he continued to show interest in puzzle feeders and regular touch-screen cognitive sessions.

Of course, Keo’s long life is a testament to the advances in zoo care we’ve seen in recent years. Daily enrichment, nutritious diets, routine checkups and world-class care have enabled geriatric animals to live longer, healthier lives than ever before.

Our veterinarians continue to harness the latest technologies to care for zoo species. A remote EKG device made it possible for veterinary experts to monitor Keo’s heart health, better informing this difficult quality-of-life decision. The EKG data ensures that Keo will leave one more legacy as it adds to the body of knowledge on how to best care for geriatric chimpanzees.

But Keo left quite a legacy regardless. He fathered 11 offspring over the years. Beyond that, though, he inspired joy and countless memories in those who shared time with him at Lincoln Park Zoo.

So farewell to Keo. We will miss him. And if you’d like to share a Keo memory—or leave a supportive message for our animal care staff in this difficult time—we ask you to do so at

Kevin Bell

Correction: The original draft referred to Keo as Lincoln Park Zoo's first chimpanzee. The zoo did have chimpanzees dating back to the 1920s, although Keo was certainly one of the longest tenured--and the most memorable.

More Keo Memories

Vicky examines the ice cakes donated by Nadeau's Ice Sculptures Inc.

Post from the President—A Chimpanzee Celebration
President and CEO Kevin Bell shares highlights from chimpanzee Keo's 55th birthday celebration and Vicky's 50th, explaining why chimpanzees across the country have other reasons to celebrate.

Geriatric animals thrive within Lincoln Park Zoo’s culture of care.

The Golden Years
Geriatric animals thrive within Lincoln Park Zoo’s culture of care.


Hank, Kathy and Nana check out the new chimpanzees across the way.

Chimpanzees Check One Another Out
There were plenty of vocalizations and activity as Hank and Keo's chimpanzee groups spotted one another across neighboring exhibits.


An Array of Apes
Enjoy these portraits of the zoo’s gorillas and chimpanzees, from babies to bachelors.

Chimpanzee Keo upends the John Hancock Center at Regenstein Center for African Apes. (Photo by Susan Andrews)

Animals Eat the Skyline at Chi-Cow-Go
The zoo celebrated Chicago’s 175th birthday with a bovine bash. The fun kicked off with the unveiling of a redesigned "Cows on Parade" statue before moving to the rest of the zoo with Chicago-themed animal enrichment. You can also watch a video of the fun!



God Bless you Keo

You were such a smart and silly boy Keo! You will be missed by everyone, but I'm sure you're enjoying your "new found youth" and acting just as goofy as ever. You will be missed by everyone.


Sorry to hear about your loss...fond memories as a child, young married living near Lincoln Park, mother. You did your best for him...he lived a long a happy life.

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