The Best Places Around the World to See Bats (by the Millions)

Bracken Cave is the summer home of the largest colony of bats in the world. From March to October, over 15 million Mexican free-tailed bats take up residence in Bracken Cave, located in the Texas Hill Country. To protect the cave from the growing San Antonio suburbs that are rapidly expanding toward it, Bat Conservation International purchased the cave, as well as 697 surrounding acres, to ensure the bats' natural habitat would remain untouched. Nightly, the bats emerge from the cave by the millions to hunt for insects, offering visitors a chance to see one of the highest concentrations of mammals on earth. Visitors can book a viewing mid-May to mid-September.

The Congress Avenue Bridge in Austin, Texas, is home to the largest urban bat colony in the world. The bridge was reconstructed in 1980, and its crevices made an ideal roosting location for bats, who began flocking to the bridge by the thousands. Residents of Austin reacted negatively at first, but soon realized that the roughly 1.5 million bats provided free pest control for the city, eating 10,000 to 20,000 pounds of insects each night.

Austin's daily newspaper, the Austin-American Statesman, supported the creation of the Statesman Bat Observation Center, on the southeast corner of the bridge, which gives visitors a place to watch the nightly fly-outs. Each year, more than 100,000 people make the trek to Austin to see the bats take off on their evening flights.

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.

Between October and December, roughly 10 million straw-colored fruit bats make their home on one hectare of the Kasanka National Park's swamp forest (for comparison, that's five times the number of wildebeests in the Serengeti migration, one of the most famous examples of mass migration in the world). Enticed by the wild fruits that grow in the park, the bats take up residence in trees, roosting during the day and searching for food by night. The straw-colored fruit bat is a subspecies found only in sub-Saharan Africa. Because they eat mostly fruit—a plentiful food source—the bats can weigh up to 11 ounces (with a six-foot wingspan) and live up to 30 years in the wild. The park is relatively accessible, as it's only a five-hour drive (along paved roads) from Zambia's capital city, Lusaka. 

Gunung Mulu National Park in Borneo is home to one of the largest cave chambers in the world, the Sarawak Chamber. But it's famous for other reasons as well: the caves are also home to more than 12 species of bats. Researchers estimate that between 2.5 and 3.5 million wrinkle-lipped bats live in Deer Cave, another huge cave complex located within the park. 

Gunung Mulu has a bat observatory, where visitors can gather each night in anticipation of the evening's exodus from the caves. The observatory is a 45-minute-to-one-hour hike from the park's entrance, so make sure to leave enough time to reach the observatory before sunset. 

Cairns, a city in Australia's second-largest state, Queensland, is home to a huge population of spectacled flying foxes—one of the largest species of bats in the world. Because of its geographic location, acting as a gateway to tropical rainforests of the north (which the bats use as their primary hunting grounds), Cairns is an appealing place for the bats to roost, which they've been doing in huge numbers for years, despite attempts by the Cairns City Council to get them to move on.

Cairns is also home to the Tolga Bat Hospital, which helps promote rehabilitation and conservation of Australian bats. The hospital is open to visitors, who can come learn about bat behavior and conservation while observing several species of bats native to Australia (including the flying fox).