A Bay Area animal research nonprofit is fighting to keep PETA out of a legal dispute over the fate of the former companion of Koko, the western lowland gorilla who famously learned sign language.

The Cincinnati Zoo sued Koko’s longtime caretaker, psychologist Francine “Penny” Patterson, and her Redwood City-based nonprofit, The Gorilla Foundation, in October seeking the return of Ndume, a male gorilla it loaned the foundation back in 1991 in hopes that he and Koko would mate.