Bats, like this big eared townsend bat, have unusually robust immune systems.
Credit: Public domain
Bats are the only mammals that can fly. They are also among the only mammals known to feed on blood. Common misconceptions and fears about bats have led many people to regard the creatures as unclean disease carriers, but bats are actually very helpful in controlling the population of crop-destroying insects.
There are more than 900 species of bats in the world. Some experts estimate the number to be as high as 1,200 species. Bats make up one-fifth of the mammal population on Earth, according toBat Conservation International.
Bats are divided into two main types: megabats and microbats. Megabats (formally, bats in the Megachiroptera suborder) include flying foxes and Old World fruit bats. They tend to be larger than microbats (Microchiroptera suborder), but some microbats are actually larger than some megabats.
Flying foxes (genus Pteropus) are the largest bats. Some species have wingspans of 5 to 6 feet (1.5 to 1.8 meters) and weigh up to 2.2 lbs. (998 grams), according to the Oakland Zoo. One of the smallest megabats, the long-tongued fruit bat (Macroglossus minimus), has a wingspan of only 10 inches (25.4 centimeters), according to the Smithsonian Institution. This bat weighs about half an ounce (14 g).
Among microbats, the largest species is the false vampire or spectral bat (Vampyrum spectrum) with a wingspan of up to 40 inches (1 meter). It weighs 5 to 6.7 ounces (145 to 190 g). The smallest bat is the bumblebee bat, according to the University of Michigan Museum of Zoology. It grows to only about 1.25 inches long (3 cm) and weighs about 2 grams (0.07 ounces).
Bats live all over the world, except for some islands, and the Arctic and Antarctica. They mostly prefer warmer areas that are closer to the equator, and they can be found in rain forests, mountains, farmland, woods and cities. Bats have two strategies for weathering the cold. Some migrate to warmer areas, while others go into torpor. In this short-term form of hibernation, a bat reduces its metabolic rate, lowers its body temperature, and slows its breathing and heart rate.
Bats roost in trees, caves, mines and barns — anyplace that provides shelter from the weather, protection from predators and seclusion for rearing the animals' young. Bats live together in groups called colonies, which contain 100 to 1,000 bats. These mammals are also nocturnal, meaning that they sleep during the day and are awake at night. Some may fly up to 31 miles (50 kilometers) to find food during their nightly journeys. In the day, they sleep upside down from trees or the roofs of caves, holding on with their sharp claws. [Flying Mammals: Gallery of Spooky Bats]
Most bats eat flowers, small insects, fruits, nectar, pollen and leaves, though it depends on the type of bat. Megabats usually eat fruits, and microbats generally eat insects.
The Malayan flying fox has a big appetite. It can eat half its body weight every day. The vampire bat outdoes even that, though, eating twice its weight in one day. The brown bat can eat up to 1,000 small insects in an hour, according to the Defenders of Wildlife organization.
Some bats will squeeze fruits in their mouths and drink the juices. Vampire bats like a juice of a different type, though. They do indeed drink blood, mainly from cattle and deer, but they don't suck blood like the legends say. Rather, they make a V-shaped cut and then lick up the blood, according to the San Diego Zoo.
Bats have some unique mating behaviors not seen in other animals. Male and female bats meet in hibernation sites, called hibernacula, where they breed. "Bats 'swarm' around in huge numbers, chasing each other and performing spectacular aerobatics," biologist John Altringham told Live Science in a 2013 article. [Related: Animal Sex: How Bats Do It]
It's not clear how the bats choose their mates, Altringham said, but it may be that females seek out the most agile males. During the swarming event, breeding pairs will go off to secluded spots in the cave to mate in private.
Researchers have found that female short-nosed fruit bats perform oral sex on their mates to prolong the act; male Indian flying foxes do the same thing to females.
Mating occurs in the late summer and early autumn, and the females store the males' sperm until the next spring. A pregnant female will carry her young for a gestation period of 40 days to six months. Then, she will give birth to one baby, called a pup. The pup will weigh about one-fourth as much as its mother at birth. Young bats drink milk from their mothers to survive, much like other mammals.
The mothers and pups stay in groups, separate from the males. The other mothers help take care of the pup until it is old enough to care for itself.
The taxonomy of bats, according to the Integrated Taxonomic Information System (ITIS), is:
- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Mammalia
- Order: Chiroptera
- Suborder: Megachiroptera, Microchiroptera
- Family: There are 16 families in the suborder Microchiroptera, and only one in Macrochiroptera: Pteropodidae, which includes flying foxes and Old World fruit bats.
- Genera: There are 187 genera of bats.
- Species: There are more than 950, and perhaps as many as 1,200 species of bats.
Many bat species around the world are threatened with extinction. The Red List from the International Union for Conservation of Nature identifies more than 250 species as endangered, vulnerable or "near threatened."
Bulmer's fruit bat is the world's most endangered bat. It is only found in one cave in Papua New Guinea. According to the Red List, there are only around 160 individuals left in this colony.
A fungus that causes a disease called white-nose syndrome has devastated bats in North America. This white, powdery-looking fungus, a member of a group of cold-loving fungi calledGeomyces, coats the muzzles, ears and wings of bats and has meant death for hundreds of thousands of the animals in the northeastern United States. [Related: Devastating Disease Found in Endangered Gray Bats]
Bats "see" using echolocation. The animals make high-frequency yells and analyze the location of objects around them by perceiving how the sound bounces back off the object. Research at the University of Bristol in the United Kingdom, published in 2011 in the journal Behavioral Processes, shows that the angle at which sound bounces back can tell the bat the object's size. To discover this, the researchers studied flight patterns of the bats after objects were placed in the animals' paths.
Some horseshoe bats can hover and pluck insects from spider webs, according to the BBC.
An anticoagulant in vampire bat saliva has been adapted for use in increasing blood flow in patients with stroke or heart disease.
- San Diego Zoo: Bat
- Smithsonian Encyclopedia: Bats
- National Geographic: Vampire Bats
- BBC Nature: Bats
- Bat Conservation International