Caribou graze on the tundra in the Arctic National Wildlife Refuge in Alaska.
U.S. Fish and Wildlife Service
San Juan Islands, Washington —
A harbor seal dines near a dock in the San Juan Islands.
Courtesy San Juan Islands Visitors Bureau
San Juan Islands, Washington —
An orca whale family swims close to shore.
Courtesy San Juan Islands Visitors Bureau
Glacier National Park, Montana —
Visitors to Glacier National Park have the chance to see everything from elusive wolves, grizzlies and mountain lions to the more common mountain goats, bighorn sheep, elk and moose.
u.s. fish & wildlife service
Glacier National Park, Montana —
Bighorn rams use their horns to batter each other in competition for mates.
David Restivo/National Park Service
Yellowstone National Park, Wyoming —
Visitors to Yellowstone National Park may spot bears in the park.
National Park Service/Jim Peaco
Yellowstone National Park, Wyoming —
Bison are the park's largest mammals, but grizzlies are perhaps the most intimidating.
National Park Service/Jim Peaco
Carlsbad Caverns, New Mexico —
Hundreds of thousands of Brazilian free-tailed bats take flight en masse outside Carlsbad Caverns at dusk to hunt insects.
National Park Service/Peter Jones
Archie Carr National Wildlife Refuge, Florida —
Florida's coastlines are crucial to the survival of several species of threatened and endangered sea turtles.
u.s. fish & wildlife service
Assateague Island National Seashore —
On Assateague and Chincoteague, barrier islands off the coast of Virginia and Maryland, the descendants of ponies brought by colonists in the 1600s roam freely through salt marshes, pine forests and windswept beaches.