It's the drive upon which the survival of each and every animal species hinges, and this BBC One offering hosted by David Attenborough examines grasslands, oceans, jungles and other distinct habitat forms across six continents, and brings fascinating perspectives on the challenges faced by all forms of fauna-from rival competitors to outright predators-in their respective and instinctive hunts for companionship. 5 hrs. On two discs. Widescreen; Soundtrack: English.