Humpback Whales reveals that the world's largest mammal can migrate 3,500 miles, from Hawaii to Antarctica and down to the equator. Cows and calves are very close for nearly a year before the latter begin to move toward independence, and grown males can either be nice escorts on the migration path or try to scare off youngsters to get at mom for mating purposes. Much of the documentary is concerned with the famous sounds humpbacks make under water--the cries and moans and clickings that scientists don't fully understand yet. Wolf says a hunting wolf is so strong that it can take down another animal 10 times its weight. Wolves are also highly intelligent and elusive, remaining mysterious despite our best efforts to understand them and how they live. Highlights of the show include great footage of a wolf pack hunting a buffalo by wearing it down over several days. Crocodile says that crocodiles have changed little from the age of reptiles, and are the only reptile predator to outlive dinosaurs. Crocodiles control their buoyancy in water by inhaling and exhaling, and are generally designed to survive anywhere in the tropics. They also, astonishingly, colonize new rivers in other parts of the world on their own, traveling through the ocean to new homes. Special features in this two-disc set include the enjoyable "Great Natural Wonders of the World" and "Greatest Wildlife Show On Earth." --Tom Keogh