The age of 50 has been reached by one of Europe's oldest chimpanzees.
Koko was born in 1973 at the Dudley Zoo in the West Midlands, and since 2006, she has resided at the Whipsnade Zoo close to Dunstable, Bedfordshire.
At the Twycross Zoo in Leicestershire, the similarly named Coco, the oldest chimpanzee on the continent, turned 58 in April.
According to the Press Association, chimpanzees kept in captivity typically reach the age of 33.
Little Mama, who passed away in a Florida safari park in 2017, was thought to be in her late 70s and is the oldest chimpanzee known to science.
Koko was in "brilliant health," according to Grant Timberlake, primate keeper at Whipsnade Zoo, but she did have a mild case of arthritis in her hands.
She was kept "pain-free and fully mobile" by low-level laser treatments.
Koko has made contributions to several significant projects aimed at protecting her species. Her heart was subjected to ultrasound examinations that helped specialists comprehend cardiovascular disease in great apes.
Together with another chimpanzee, Koko briefly escaped her enclosure in 2007.
Johnnie, another escapee, was killed because he posed a threat to the public, but she was eventually captured.
While Gladys the flamingo, who will turn 53 in July, is the zoo's oldest animal, Koko is the oldest mammal at Whipsnade.
