What drives Yellowstone's massive elk migrations?

Every spring, tens of thousands of elk follow a wave of green growth up onto the high plateaus in and around Yellowstone and Grand Teton national parks, where they spend the summer calving and fattening on fresh grass. And ...

What is pepper spray?

Whether it's walking down a dark street at night or fighting off grizzly bears on the trail, pepper spray is an effective tool to fend off an attacker and get safely away. But have you ever thought about what gives this personal-defense-in-a-can ...

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