This week's dirt: animal chemical warfare, what horse DNA tells us about the domestication of the horse, the growing problem of pythons in the Everglades, heightened demand in the ivory market, and more.

While legend paints the wolverine as a solitary, blood-thirsty killer, there is another, more complex image of the wolverine that is just beginning to emerge.

Sound Recordist Dave Ruddick goes through his set-up and explains how he records surround sound in Tongass National Forest. A behind-the-scenes look at what goes into the making of a nature documentary.

After the tides have proven a challenge during a shoot on Admiralty Island, the film crew has to get creative in order to keep their boat from getting stranded. A look at the challenges that can pop up when filming nature documentaries.

Filmmaker Shane Moore and Assistant Cameraman Michael Mauntler recap on the time they spent on Alaska's Admiralty Island and discuss the challenges that come with filming bears in their natural environment.

Fortress of the Bears filmmaker Shane Moore on some of the filming techniques he used during his shoot on Alaska's Admiralty Island. A behind-the-scenes look at what goes into the making of a nature documentary.

New insights about a species that is far more smart and wily than most ever imagined. Is city life cultivating “über-raccoons,” ready to take over the world? Watch a preview of PBS Nature's Raccoon Nation.

This week's dirt: the evolutionary advantage of sightless cave fish, iridescent blind moles, the domestication of bonobos, the benefit of black feathers in flight, and more.

Preview the first few minutes of "Wolverine: Chasing the Phantom." Hardy, elusive, and smart, the wolverine dominates the harsh Alaskan wilderness.

Enter a world shaped by bears, trees, and salmon. Watch the full episode of PBS Nature's Fortress of the Bears.