Amazing bats of Bracken Cave

The sun is setting on a summer night. At the entrance to a deep, dark cave, a few bats fly out and begin swirling high up into the air. More and more of the small, furry creatures appear.

Within a few minutes, a whole river of bats is pouring out of the cave, and they keep coming, millions and millions of them.

Sound like a scary horror movie? Believe it or not, this scene takes place every night, all summer long, at Bracken Cave in Texas, where 20 million bats zoom outside to feed on insects. “It is magical,” says Jim Kennedy of Bat Conservation International in Austin Texas. “It is one of the most majestic animal movements on the planet.”

A group of bats is called a colony. Every March or April, Mexican Free-tailed bats (tadarida brasiliensis) migrate up to 1,000 miles from their winter home in Mexico to this cave, where they raise their young. Soon after they arrive, each mother gives birth to one pup. As many as 500 baby bats live crammed into one square foot of space, and all those bodies create nice warm temperatures to keep them cozy and comfortable.

If you’ve ever lost sight of your parents on a crowded playground, you may be wondering how mother bats recognize their offspring. They use their sense of smell to tell which pup is theirs when it is time for the babies to nurse.

The cave, a quiet place in winter, teems with life all summer—and not just with bat residents. Bat poop, called guano, soon covers the floor, providing food for tiny organisms like bacteria and fungi. And then there are the bugs, says Kennedy: “You walk in with your headlight on your helmet on, and the floor of the cave is seething with bugs. Gnats are flying around, and beetles are crawling up your leg!”

When the adult bats leave the cave at night to feed, they are helping humans. They eat tons of insects in a single night, including many pests that eat farmer’s crops. And they get rid of mosquitoes, too.

When twenty million bats fly out of one cave opening, they make a column so thick that they show up on radar at the nearby airport. It can take three hours for all of them to emerge. “You can feel the breeze from their wings, and see the vegetation rustle,” says Kennedy. “The flap of all those wings makes a very relaxing soft sound. I’ve always thought it would make a great tape to help you go to sleep.”

So much for bats being scary!

While much of the world sleeps, vampire bats emerge from dark caves, mines, tree hollows, and abandoned buildings in Mexico and Central and South America. They glide stealthily through the night air as they search for food. Like the legendary monster from which they get their name, these small mammals drink the blood of other animals for survival. They feed on blood from cows, pigs, horses, and birds. Though uncommon, vampire bats occasionally bite humans for blood. Rather than sucking blood, vampire bats make a small cut with their teeth and then lap up the flowing blood with their tongues. These bats are so light and agile that they are sometimes able to drink blood from an animal for more than 30 minutes without waking it up. The blood sucking does not hurt the animal. Vampire bats have special adaptations to help them with their unique feeding needs. Unlike some other species of bats, vampire bats can walk, run, and jump. They have very strong hind legs and a special thumb that helps them take off after feeding. Also, heat sensors on their noses help them find a good spot on an animal's body to feed. What happens if vampire bats don't get their nightly meal? If they can't find blood for two nights in a row, they will die. Luckily, female bats can be generous. Well-fed bats will often regurgitate blood to share with others in exchange for grooming. Female bats in captivity seem especially friendly toward new mothers. After a baby is born, other bats have been observed feeding the mother for about two weeks after the birth. Are vampire bats really that scary? Even though bat bites themselves aren't harmful, vampire bats can spread a disease called rabies. This disease hurts farmers' livestock, especially cattle herds. However, vampire bats can actually be quite tame, and even friendly to humans. One researcher reported that he had vampire bats that would come to him when he called their names.

A two-inch-long tube-lipped nectar bat hovers by a narrow, bell-shaped flower in its forest habitat. This hungry animal is after nectar at the bottom of the blossom. To get to the goody, the bat pokes its snout into the flower. With the nectar still out of reach, the mammal sticks out its tongue, which is one-and-a-half times the length of its body. After licking up the sticky sweet, the bat retracts its jumbo-size tongue and flies off. TRANSFORMING TONGUE The tube-lipped nectar bat was first discovered in Ecuador, a country in South America. It has the longest tongue compared to its body of any mammal in the world. In fact, if this bat were a person, its tongue would be almost nine feet in length! The bat stores the extra-long licker in its chest until it comes across a flower with yummy nectar inside. Once the animal’s tongue reaches the nectar in the blossom, the tip transforms. Hairlike bristles on the tongue stretch outward, making it prickly. With these bristles extended, the bat can extract more food from the plant. By chowing down on flower nectar, these animals don't just satisfy their hunger—they also help maintain their habitat. POLLEN POWER As the tube-lipped nectar bat eats from the flower, it brushes against the petals. This causes pollen from the blossom to fall on the bat’s head. The bat sprinkles the pollen from the flower on the next plant it visits. This can lead to the creation of seeds, which get dispersed and grow into new blossoms. Who knew bats were good at gardening? Watch a video of the tube-lipped nectar bat. Text by Andrea Silen, NGS Staff

Amazing bats of Bracken Cave

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