An MMA fighter was offered £370,000 to take on a chimpanzee, with warnings about life-changing harm.
Cole Johnson said the initial joke became a real fight.
The event appeared to be cancelled after its website went offline over trust and safety.
It was subsequently labelled as a crypto hoax.
In a separate case, nine chimpanzees on Ngamba Island selected a baited box on 73 percent of trials when a human pointed, called names and made food grunts.
Pointing alone had no such effect.