What does the growl at the end of Kingdom of the Planet of the Apes mean?

Kingdom of the Planet of the Apes

+Anything Extra? Yes

From the RunPee app

Anything Extra?

At the very end of the credits there is an audio-only extra. There is the sound of an ape growl. It's not worth the wait.

The credits run for approximately 8 minutes.

At the end of the credits in Kingdom of the Planet of the Apes we hear an audio only extra that clearly is meant to tell us something, but what. The sound appears to be the same that an orangutan makes. Since Raka is the only orangutan character in the movie, it appears the audio extra teases that Raka has somehow survived.