Catalyst: Wildlife migration corridors

Biologists install digital cameras and microphones around wild habitats to observe where endangered animals migrate. By mapping wildlife movements conservationists can advise governments how to build infrastructure that protects biodiversity.

WATCH: See more from season 2 of “Catalyst”

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Catalyst: Acoustic Ecology Lab

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Andy Martinez

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American Veteran “The Crossing”

Veterans reflect on and share their personal experiences in the military, from boot camp to service in war and peacetime to return to civilian life.

American Masters: Becoming Helen Keller

Explore how Keller used her celebrity and wit to advocate for social justice, particularly for women, workers, people with disabilities and people living in poverty.

Great Performances: Now Hear This "Beethoven's Ghost"

Go inside the mind of a genius as host Scott Yoo and fellow musicians undertake a recording of Beethoven's most personal music at a historic Berkshires manor to explore the composer’s brilliant career—where they are visited by some unexpected guests.