This episode features perhaps the most extreme case of prehistoric animals interacting with the camera: the indricothere calf charges at the camera-man, knocks the camera over, and walks away from the scene that has been flipped 90° to the side as a result of the collision.
The sounds of the indricothere were a combination of bear and rhino sounds. According to the audio-editing crew, the sound produced by the entelodont was the most complicated of all the animals - it was made by mixing together a bunch of different animal sounds, similar to the engine noise of the Tie fighters of the Star Wars movies. The calicothere sounds were actually hippo grunts, the favorite animal sound of the crew from this series, as they claim on the BBC website.
Featured creatures: Indricotheriun, Chalicotherium, Moeritherium, Entelodon, Hyaenodon, Cynodictis (bear dog). The book also features Nimravus (cat-like predator), Eogrus (bird eating dermal parasites off Indricotherium's back) and Hyracodon (goat-sized relative of Indricotherium).
The behavior of Indricotherium was based on its modern-day relative, the rhinoceros.
The sound of the bear dog is, appropriately, a dog.