Bats

Bat Facts

Classification:

Kingdom: Animalia

Subkingdom: Metazoa

Phylum: Chordata

Subphylum: Vertebrata

Class: Mammalia

Subclass: Theria

Order: Chiroptera (bats)

Suborders: Megachiroptera (flying foxes), Microchiroptera (bats)

Families: Craseonycteridae (hog-nosed bats), Desmodontinae (vampire bats), Emballonuridae (sheath-tailed bats), Furipteridae (thumbless bats), Hipposideridae (Old World leaf-nosed bats), Megadermatidae (false vampire bats), Molossidae (free-tailed bats), Mormoopidae (leaf-chinned bats), Mystacinidae (short-tailed bats), Myzopodidae (sucker-footed bats), Natalidae (funnel-eared bats), Noctilionidae (bulldog bats), Nycteridae (slit-faced bats), Phyllostomidae (New World leaf-nosed bats), Pteropodidae (flying foxes), Rhinolophidae (horseshoe bats), Rhinopomatidae (mouse-tailed bats), Thyropteridae (disk-winged bats), Vespertilionidae (common or vesper bats)

Geographical location: Every continent except Antarctica

Habitat: Mostly forests and deserts; some grasslands

Gestational period: Three to ten months, with delayed implantation

Life span: Generally three to five years; up to thirty years in captivity

Special anatomy: Head, body, tail; two wings supported by upper arms, forearms, and hands; knee joints that bend backward, enabling the bat to hang upside down and still be ready to take flight easily

Bats are difficult to study because of their secretive, nocturnal habits and flight capabilities. Although over twelve hundred species have been identified and cataloged, additional species continue to be discovered. This occurs primarily in the South American rainforests. The classification of bats continues to improve.

Bats are the most widely distributed kind of terrestrial mammal. They are found from Alaska to the tip of Argentina and from near the Arctic Circle to South Africa. They occur widely throughout the tropical regions and in the temperate zones.

Physical Characteristics of Bats

Although bats range in size from tiny hog-nosed bats that weigh less than a penny to flying foxes whose wing spans exceed five feet, the majority of bats tend to be small. Despite variation in size, all species of bat share the same body form, with certain similarities in fur, skin, wings, teeth, reproductive system and patterns, and visual and hearing systems.

The bat’s skin is black or dark grayish brown in color, with tiny transparent hairs on the membrane surface. Most bats have small eyes, perhaps encouraging the misconception that bats are blind, while their auditory system is developed to an extraordinary degree.

Of the bats who feed on animals, some feed on insects and whole animals; vampire bats, which occur from Mexico to Argentina, feed only on the blood. Plant-eating bats feed on fruit and flowers.

Female bats give birth at their roost site, frequently while hanging upside down. They are placental mammals, meaning that the fetus fully develops within the female's uterus. Bat young are born in a breech presentation and are helpless until they are large enough to fly. Brown bats reach adult size and begin to fly at three to four weeks of age.

The Behavior of Bats

The major behavioral pattern of bats is nocturnal activity. During nocturnal flight, bats are protected from being visually spotted by predators and from exposure to the sun and high temperatures, which promote heat absorption and the loss of body water necessary for temperature regulation.

Bats routinely seek shelter during the daylight hours. Caves provide protection from the sun and predators and allow bats to conserve energy under consistent temperature and moisture conditions. Bats also shelter in tree cavities, crevices, buildings, and trees.

While tropical bats are active all year round, bats in temperate regions hibernate during the winter in order to accommodate the diminished food supply. Most hibernating bats spend the summer feeding heavily on insects, building up enough fat to provide energy during hibernation. During hibernation, the bat allows its body temperature to fall to that of the surrounding air, and as its pulse and breathing rates slow down, it essentially enters a state of suspended animation.

The sole characteristic that sets bats apart from other mammals is flight. Some bats fly high, fast, and far, while others fly more slowly, maneuvering around obstacles, catching their prey on the wing, or plucking it from the ground. Soaring is uncommon in bats, as is swift flight in comparison with birds. Bats fly in flocks, sometimes numbering in the thousands, a precaution against predators.

Microchiropteran bats use echolocation, a pulse system of high-frequency sounds and their echoes, to navigate and to locate food. Bats emit sound, and then analyze the data from the returning echoes. This provides them information on direction and distance to the target. Best suited to short distances, echolocation is so accurate that some bats appear able to distinguish among individual species of insects.

Bats are allies of human beings in controlling the insect population. Most species of bats in the United States feed on beetles, moths, and crickets, many of which destroy vegetation and damage agricultural interests. Recent studies also suggest important uses for the anticoagulant compounds found in vampire bats’ saliva that hinder the clotting of blood.

In February 2006, cases of white-nose syndrome (WNS), a deadly fungal disease, began appearing among the North American bat population; it was first identified the following winter. The disease is caused by the cryophilic fungus Pseudogymnoascus destructans (formerly Geomyces destructans), which thrives in the cold, damp environments in which bats prefer to hibernate, and has demonstrated a 90 to 100 percent mortality rate, mainly among the Myotis lucifugus, or little brown bat. The fungus drains hibernating bats' energy and fat stores too quickly, leading to their deaths. As of 2016, WNS was known to affect seven hibernating species in the United States and Canada, with five others known to carry the fungus without developing the disease. Scientists have found that exposure to the bacterium Rhodococcus rhodochrous prevents the growth of the fungus and increases infected bats' chances of survival, although as of 2016 the researchers had yet to figure out a method of delivering this treatment outside of laboratory conditions. The fungus has also been found to be vulnerable to short bursts of ultraviolet light, but the issue of how to deliver this treatment to the bats remains. Bats in areas heavily affected by WNS have also adapted by putting on more weight before hibernating, leaving them better able to survive the strain the fungus puts on their systems.

In 2023 researchers have expressed concern about declining bat populations. One report suggested more than half of bat species in North America were at serious risk. Climate change and drought were believed to be major contributors to this situation as well as encroachments into natural bat habitats. As bats provide essential services to human populations, such as insect control and pollination of food plants, such a population decline would also have multiple adverse effects on human populations.

Principal Terms

insectivorous: depending on insects for food

mammary glands: glands in female mammals that secrete milk

nocturnal: active during the night

placental: a type of mammal whose young are enclosed in a membrane inside the mother’s body during pregnancy

terrestrial: relating to the earth

vertebrate: an animal that has a spinal column

Bibliography

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