Wildlife migrations around the globe is the fascinating subject of the third part to National Geographic's enormously ambitious epic documentary series, Great Migrations. This seven-part series is narrated by Alec Baldwin and features shockingly impressive photography, often tackling subjects that are really hard to photograph — like tiny baby crabs, butterflies, ants, birds, as well as your standard large-mammal fare.

The habitual behavior of the creatures -- red land crabs on Christmas Island, butterflies in Mexico, zebras and wildebeests in Africa, penguins in Antarctica and Sperm whales in the seas are among the animals that cover vast distances as they follow the annual habitual migratory routes that seem to be imprinted in their DNA.