Giving voice to the world's animals

Martyn Stewart has spent more than 50 years capturing the sounds of creatures from around the world. Some of those animals are now extinct. Stewart wants to protect what we have left.

Katy Sewall of "The Bittersweet Life" podcast spoke with Stewart and brings us this audio postcard.

To hear sounds of the natural world recorded by Martyn Stewart, go to The Listening Planet.