It's Animal Week on Fresh Air; during these last days of summer, we're featuring rebroadcasts of our best conversations about animals and how we live with them.

Film directors Alastair Fothergill and Mark Linfied follow the movement of polar bears, elephants and humpback whales in their new film, Earth.

Shot at 200 different locations in 64 different countries, Earth covers a vast terrain that ranges from the tops of mountains to the bottom of the ocean. The film was five years in the making.

Fothergill and Linfield also directed the BBC series Earth and the Discovery Channel series Planet Earth. The duo says that while the TV series were "habitat-based," the new film is "character-based."

This interview was originally broadcast on April 22, 2009.

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