It is at the same time both one of the most striking fish you'll encounter as well as one of the most dangerous to appear in the waters of Biscayne National Park.

What some call the most beautiful mating ritual on the planet takes place at Great Smoky Mountains National Park in June when synchronous fireflies do their thing.

The Asian swamp eel is prolific, hardy, voracious, ecologically disruptive, and on its way to becoming the scourge of the Everglades. Is it already too late to stop it?

Yellowstone National Park is "charismatic mega-fauna" defined. Spend a handful of days in the park and you're likely to spy wolves, elk, grizzlies, black bears, moose and more. But salamanders?

If you've ever heard a frog doing its “ribbet” thing anywhere along the Pacific Coast, it's probably been a Pacific Treefrog. And if you’ve ever seen one of these little critters up close, you know why many consider it one of the most fascinating of all the amphibians.

Big Bend National Park is remote and dry – not exactly a place that most people think of right away when they plan a vacation. But the desert is full of interesting things, some of them so small that they might escape notice. Take, for example, the ghostly Texas banded gecko.

The American Marten is a rare North Woods animal that you'll probably never see, save for paw prints in the snow. This brown, bushy-tailed little critter, which looks something like a cross between a mink and a house-cat, was prized for its luxurious fur and darn near trapped to extinction in the United States during the 19th century. Today, despite habitat losses and related problems, the American Marten still inhabits much of its historical range.

The red-throated loon is the smallest, most widely distributed, and most distinctive of the world’s five loon species. Annually migrating from summer nesting sites in the Arctic reaches of North America and Eurasia to wintering grounds in the Lower 48, Mexico, Europe, and Asia, this bird can really move.

A tiny clutch of islands in the South Pacific harbors not only the National Park of American Samoa, one of the National Park System’s oft-overlooked delights, but also some of the last vestiges of the many-Colored Fruit Dove, a colorful bird that long has captivated those lucky enough to spy it.

Despite their curious name, “hellbenders” are not demons of the night but rather amphibious environmental monitors of Southeastern creeks and streams. Known to some old-timers as “walking catfish,” these super-sized salamanders gained the “hellbender” moniker for their freakish size and dark, moody color.