A cheeky orangutan made it clear what he thought of these visitors to a Washington, D.C. zoo: by taking a massive dump on their heads.

The incident happened at National Zoological Park where the orangutans are usually kept indoors.

But, according to the filmer, the animals are allowed at certain times to roam free across ropes above a pedestrian walkway.

"We wondered why there was a yellow caution box painted underneath the ropes. We know now!" says Joanne, the filmer.

The footage was captured last month.

++CLIENTS PLEASE NOTE: THIS VIDEO HAS BEEN EDITED++

Orangutan takes dump on spectators at the zoo.

This was at the Smithsonian zoo in Washington DC. It was filmed by myself on my cell phone. My family and I were at the Orangutan section of the zoo. Orangutans are usually indoors but they let them out at certain times to roam freely. The ropes he is on goes over a pedestrian crosswalk within the zoo. Spectators were captivated to see him roaming freely across the ropes. Everyone staring in awe when out of nowhere...well the video speaks for itself. The orangutan relieved himself right on top of his visitors. The reaction from the crowd could be heard to include myself with surprise and laughter in both English and Spanish as to what just occured. No wonder they had a yellow caution box painted underneath on the crosswalk.....We know now.