Koko the gorilla is famous for having learned a large number of hand signs from a modified version of American Sign Language.
But less well known is the fact that she absolutely loves babies - despite not having had the opportunity to have any of her own.
She often signs the word "baby", carries gorilla dolls in her arms, and even pretends that her dolls can sign by moving their arms and hands.
So in celebration of the ape's 44th birthday, her trainer Francine Patterson introduced her to some other babies - a litter of kittens.
During her meeting with the kittens, she made the sign for "cat" followed by "baby" - telling her trainers the kittens were now her adopted children. She also asked in sign language for one of the kittens to be placed on her head.
Despite her huge hands being the size of the young cats, Koko was gentle with the tiny balls of fluff when they arrived in a cardboard box, carefully flicking a finger out to stroke them.
Koko was filmed being presented with a cardboard box containing the kittens, and taking a peek inside it, at the foundation's California base.
Footage shows Koko taking her time before attempting to pick one of the kittens up - as if allowing them the chance to acclimatize to her first. She then scoops up a little grey kitten in her hand. After bringing the cat up to her face to take a closer look, the gorilla strokes its belly with her index finger before tucking it under her arm for a cuddle.
Later, another little kitten is filmed desperately trying to get out of an animal carrier bag in order to snuggle up to the great ape. The clip concludes with Koko gesturing for one of the cats to be placed on her head before later signing that the animals are her babies.
The adorable video was posted to YouTube via the kokoflix account and is further evidence of Koko's "greatest wish" - to have a baby of her own. Information provided alongside the video states that the gorilla and two of the kittens are now part of one happy family.
According to Koko's trainer, the special ape is able to understand more than 1,000 signs of what Patterson calls "Gorilla Sign Language". Koko was also exposed to spoken English from an early age and is reported to be able to understand approximately 2,000 words of the spoken language.
Koko has also previously expressed a love for kittens, asking foundation workers for a cat for Christmas in 1984 via her "sign language".
- Daily Mail