Koko the gorilla recently turned 44 years old, and to celebrate, the staff at the Gorilla Foundation in Redwood City, California, surprised the gorilla with a box containing a litter of kittens to play with.
Koko's maternal instincts kicked immediately in as she interacted with the tiny kittens.
Koko gently picked up a small gray kitten named "Ms. Gray" from the box, cradling the feline in her arm, stroking its belly, and even asking a trainer to place Ms. Gray on her head.
The gorilla used sign language to communicate to her trainer that the kittens are her babies, and the staff let Koko keep Ms. Gray, as well as another kitten named "Ms. Black" to raise as her own.
In an email newsletter, the Gorilla Foundation stated that after adopting Ms. Gray and Ms. Black, Koko has been more energized, and is "signing more than ever."
"We are demonstrating that Koko’s empathy for other species is ongoing, just as our empathy for gorillas must be too," wrote Penny Patterson, president and director of research.
Koko knows over 1,000 words in sign language and understands over 2,000 words of spoken English, according to the Gorilla Foundation.
The gorilla has been a fan of kittens since she adopted her first kitten, All Ball, in 1983.