Carlsbad Caverns, New Mexico
Seventeen different species of bats call the Carlsbad Caverns home. From spring to fall, a large colony of Mexican free-tailed bats takes up residence in the park's caverns, emerging nightly to hunt for insects. But not all of the bats actually live in the caverns—some make their home in trees, while others roost in cracks in cliffs throughout the park.
Though bats live in the park from April to October (depending on the weather), the best time to see bat flights at the Carlsbad Caverns is in July and August, when baby bats, who were born earlier in the summer, join mature bats for nighttime flights. If you can't make it to the park by sunset to see the nightly fly-out, consider getting up early to watch the bats return to the caverns—an equally impressive sight.