Chicago's Lincoln Park Zoo announced on Monday that they had euthanized Keo, the oldest living male chimpanzee in any North American zoo.
According to a zoo news release, Keo, who was 55, was the zoo's first chimpanzee and arrived in Chicago in 1959 at the tender age of one. Since then, the geriatric chimp fathered 11 offspring.
Keo had an advanced heart disease that was impacting his quality of life, the zoo said Monday, which prompted the difficult decision. He "will be missed dearly."
"Keo was an incredibly special individual," Maureen Leahy, the zoo's curator of primates, said. "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."
Kevin Bell, the zoo's president, added that Keo "inspired joy and countless memories in those who shared time with him at Lincoln Park Zoo."
The median life expectancy for a chimpanzee is almost 32 years -- so to say Keo lead a full life is putting it lightly. You'll be missed, pal!
Watch Keo in action, munching on cake and generally being a pretty jolly fellow, at his 50th birthday party in 2008: