"We came across a wild orangutan hanging over the river on our way to Camp Leakey, who joined us in the boat," the uploader wrote.
The orangutan appears unafraid of the humans and approaches them to receive some offered snacks.
The primate appears content to take food from the hands and mouths of the men, but seems suddenly annoyed when one of the men attempts to take a selfie with it.
The orangutan slaps the man in the face and quickly backs away from him.
"He just slapped me, like, right on the nose!" the uninjured man says through laughter.
The orangutan hangs out at the back of the boat for a little longer before climbing back into the trees.