Nearly one-quarter of the northern elk herd at Yellowstone National Park is missing, according to the annual winter count, but biologists aren't sure if there's been a stunning decline in the herd or if other factors have skewed the tally.

National Park Service stores sell books, photographs, postcards and T-shirts. But every once in a while, you can also discover some gems, both silly and fascinating, in the visitor center stores. What have you found?

While mule rides will continue at Grand Canyon National Park under a new stock use plan, only 10 visitors a day will be allowed to ride below the South Rim, a decision lamented by some who say it will deprive many of venturing into the canyon's Inner Gorge.

How best can Black Canyon of the Gunnison National Park be photographed? Let professional photographer QT Luong highlight the way for you.