Walking with Beasts, marketed as Walking with Prehistoric Beasts in North America, is a 2001 six-part nature documentary television miniseries created by Impossible Pictures and produced by the BBC Science Unit, the Discovery Channel, ProSieben and TV Asahi. The sequel to the 1999 miniseries Walking with Dinosaurs, Walking with Beasts explores the life in the Cenozoic era, after the extinction of the non-avian dinosaurs, particularly focusing on the rise of the mammals to dominance.

Whale Killer is the second episode of Walking with Beasts series. It takes place at the end of the Eocene-start of the Oligocene epochs. This is a time of an extinction event so unlike the previous episode, which was featured on the beginning of mammal evolution in general, the episode shows extinction of many first (archaic) mammal families instead. The second episode is set during a cooling period in the late Eocene, which drastially changed the ocean currents and climate. Climate change impacts different animals in different ways. On land, the giant predatory mammal Andrewsarchus is driven to the beach to feed on sea turtles and a herd of Embolotherium struggle to survive. In the ocean, a mother Basilosaurus struggles to keep herself and her newborn calf fed, failing to hunt both Moeritherium and Apidium after being forced to swim in to a mangrove swamp in search for food.