LINCOLN PARK — Lincoln Park Zoo's first chimpanzee, Keo, the oldest male chimp in a North American zoo, was euthanized Monday.
Keo, who was 55, came to the zoo as a baby in 1959 and fathered 11 offspring.
The zoo said it euthanized Keo because he suffered from advanced heart disease, which had compromised his quality of life.
“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 in a statement from the zoo. “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.”
Keo had lived behind the scenes at the zoo's Regenstein Center for African Apes in recent years, but his 55th birthday this summer was celebrated with a giant 1,500 pound ice-carved "cake."
The median life expectancy for male chimpanzees in zoos in 31.7 years, according to the zoo, and the oldest a chimp lived to be in a zoo was 61 years.
"Advanced cardiac disease had irreversibly compromised the quality of Keo’s life. And so it was time to say goodbye," said zoo president Kevin Bell.
The zoo is crediting Keo with helping veterinarians advance their research, as the chimp had a remote EKG device that allowed experts to monitor his heart health.
“Keo was always full of personality, even as his health began to decline,” said Steve Ross, director of the Lester E. Fisher Center for the Study and Conservation of Apes.
Even in his old age, Keo continued to perform touch-screen cognitive sessions.
Lincoln Park Zoo has set up a memorial website for Keo where visitors can leave a message or share a memory here.