The video shows the officer walking away from the ram, which responds by darting between the man's legs, nearly knocking him off balance.
The laughing officer does not appear to have been injured by the brief "assault."
"HAVE YOU SEEN THIS SHEEP?" the Facebook post said. "Police would like to speak with him in relation to an assault on a police officer on the North Shore. He is described as being of medium build, with white hair that has been recently shorn. Please approach with caution and call us immediately if you know where he is."