He spent 18 months in the Congo filming gorillas for "Lords of the
Forest" (US: "Masters of the Congo Jungle"), narrated by Orson Welles.
It was considered a landmark film in showing apes as social animals and
not violent beasts.
His 30-year German TV series "Expeditionen ins Tierreich" ("Expeditions
into the Animal Kingdom") made him a household name. He worked with
National Geographic to produce several documentaries in the 1960s and
70s that were shown around the world.
His first film was a documentary on birds, completed in 1938. In 1955,
he made a feature film about woodpeckers, which earned him the nickname
"Mr. Woodpecker".