The world's most intelligent gorilla came close to tears after hearing of Robin Williams' death.
The famed gorilla, Koko, who can communicate in sign language, met Williams 13 years ago when he visited The Gorilla Foundation in California.
The pair became "very special friends", according to staff at the foundation.
During the visit, Koko was said to have laughed for the first time since her gorilla companion passed away six months prior, the Daily Mail reported.
After news broke of the 63-year-old Hollywood actor's death, Koko picked up on the sombre mood at the centre.
"After the first call, Koko came to Dr [Penny] Patterson with an inquiring look on her face," the foundation wrote. "Dr Patterson explained that 'we have lost a dear friend, Robin Williams'. Koko was quiet and looked very thoughtful."
By the end of the day, after more calls came in, Koko bowed her head, and her lip quivered. Handlers said she was close to tears.
"She became extremely sad.
"Robin's ability to just 'hang out' with Koko, a gorilla, and in minutes become one of her closest friends, was extraordinary and unforgettable," the foundation wrote.
It said Williams was not only one of the world's most beloved entertainers, he was also a powerful ambassador for great ape conservation.
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