By Julie Watts

SAN FRANCISCO (KPIX 5) —┬áKoko, the gorilla famed for her ability to use human sign language, died this past summer. But now there is a legal battle brewing over the future home of her longtime companion.

Ndume was hand selected by Koko. Since 1991, the two were friends and neighbors, living in separate enclosures the Gorilla Foundation property in the Santa Cruz.

But after Koko passed away during this past summer, the Cincinnati Zoo — where Ndume was born — said it was time to send him home.

“We’re talking at least four months now since Koko passed away that he’s been living in total isolation,” said Cincinnati Zoo primate curator Ron Evans.

He says, according to their loan agreement with the Gorilla Foundation, Ndume was supposed to be moved to an accredited zoo upon Koko’s death.

On Thursday, the Cincinnati Zoo filed a suit in a San Francisco court to have Ndume returned.

The Association of Zoos and Aquariums recommended that Ndume be transferred back to Cincinnati where some of his relatives still live

“A foundational need for an animal like a gorilla is to have company of other gorillas,” said Evans.

The Gorilla Foundation did not respond to our interview requests and its Palo Alto offices were locked Friday.

But in a letter obtained by Cincinnati Enquirer, the Foundation argued they know what’s best for Ndume, who they have taken care of for 27 years.

They also said the geriatric gorilla has a medical condition that makes the move back to the Cincinnati Zoo dangerous, if not fatal.

PETA’s Deputy General Counsel Delcianna Winders believes Ndume should be returned to the zoo, but admitted there is not much legal precedent to the case.

“It does have similarities to custody battle over human,” said Winders. “He was born at the Cincinnati Zoo, he has family members at the Cincinnati Zoo and we’re looking at what’s in his best interest.”

She also said she was unaware of any health issues that would prevent the relocation.

“We have seen no evidence of veterinary conditions that would harm him during travel,” said Winders.

In the letter from the Gorilla Foundation that the Cincinnati Zoo included in their complaint, the Foundation claimed that Ndume overheard officials talking about returning him to the zoo and he became agitated. The letter said the gorilla proceeded to cry and bang objects for hours.