AMERICAN LEAF-NOSED BATS: Phyllostomidae

PHYSICAL CHARACTERISTICS

American leaf-nosed bats, also called New World leaf-nosed bats, are made up of diverse species. They range from small to large, with a combined head and body length of 1.6 to 5.3 inches (4 to 13.5 centimeters). This family includes the largest species of bat in the Western Hemisphere, the spectral vampire bat. These bats have a wingspan of about 3 feet (1 meter).

Some species have visible tails that are as long as 2.2 inches (5.5 centimeters), and others have no tail. These bats have noseleafs, meaning fleshy protrusions on the nose. Some of these species have noseleafs that are almost as long as the head, such as the sword-nosed bat. In most species, the noseleaf is a relatively simple structure shaped like a spear. Many species have bumps, warts, and other protrusions on the head near the noseleaf or on the chin.

The size and shape of these bats' heads vary widely and reflect their diverse feeding habits. Fruit-eating bats, for example, may have a medium-sized noseleaf, flat faces, and wide teeth to crush fruit. Bats in this family that lap up nectar (sweet liquid produced by plants) have a small noseleaf, long tongue, and small teeth. Species in this family that eat meat are generally large and have sharp teeth.

Fur color of American leaf-nosed bats is generally brown or gray, with the exception of one species, the white bat. Some species have color patterns that include stripes on the head or back, or white tufts of fur on the shoulders.

GEOGRAPHIC RANGE

These bats are also called New World leafnosed bats because of where they are found. The New World is made up of North America, Central America, and South America. American leaf-nosed bats are found in the southwestern United States south to northern Argentina, the West Indies, and central Chile.

HABITAT

Most American leaf-nosed bats live in the forest. They can live in forests that range from the dry to the tropical (hot and humid). Some species live in deserts. Many species roost (settle or rest) in caves or the hollows of trees. Other roosts include hollow logs, under tree roots, mines, tree foliage, and houses. Some species form tents out of leaves, settling under the tent for protection and rest.

DIET

American leaf-nosed bats eat a broad range of foods and groups in the family are generally categorized by diet. Most species eat animals, with the smaller species eating insects and other arthropods (a group of invertebrates that have a segmented body and jointed limbs) and the larger species feeding on frogs, lizards, birds, and other bats. Other species eat nectar and fruit. Some bats frequently eat insects and fruit. Just three species feed on blood.

BEHAVIOR AND REPRODUCTION

American leaf-nosed bats typically form colonies (groups), yet the numbers in the groups vary widely both within and among species. Sizes of groups range from pairs to colonies made up of several hundred thousand individuals.

BLOOD-SUCKING STORIES

Long before Bram Stoker's Dracula was published in 1897, there were stories about vampires. In many human cultures, vampires are people who return from the dead to feed on the blood of living people. When Spanish explorers spotted vampire bats when they came to Central and South America in the 1500s, they noticed how their feeding off the blood of other animals was similar to the vampires of their own legends. A few hundred years later European explorers traveling in the New World discovered these bats and brought them back to Europe. The bats were given the common name vampire bats, after the vampire myths. Stoker, who lived in England, was one of the people fascinated with the stories of vampire bats and incorporated them into his story. With the popularity of the novel, bats in general soon became associated with the blood-sucking vampires and this stigma continues in modern day.

All species of American leaf-nosed bats use echolocation (eck-oh-loh-KAY-shun) to detect objects and catch their prey (animals hunted for food). Echolocation is when an animal emits (sends out) high-pitched sounds that bounce off an object and return to the animal, which can then tell where the object is. These bats emit echolocation calls through their nose rather than their mouth.

Mating and reproduction vary widely among the species. Spectral vampire bats mate monogamously (muh-NAH-guh-mus-lee), meaning a male and female mate only with one another. The most common mating system is harem polygynous (HARE-um puh-LIJ-uh-nus), meaning one male mates with multiple females. Females in this family have one offspring either once or twice a year.

AMERICAN LEAF-NOSED BATS AND PEOPLE

Many of these bats are important pollinators for plants, meaning they disperse pollen, the fine grains that contain the male reproductive cells of seed plants. These bats help forests' and plants' continued survival. Through deforestation and destroying these bats' natural habitat, people have caused the decline in many of these bats' populations. Much of the negative myths and superstitions about bats come from the three species in this family that feed on blood. These vampire bats are considered pests to many farmers and feared for the spread of rabies.

BATTY FOLKLORE

Ancient artwork and hieroglyphics (high-ruh-GLI-fix; a writing system that uses pictures instead of letters) have shown that many cultures in the New World had stories about bats in this family. Representations of bats show these bats have a characteristic noseleaf. Many show bat traits added to a human figure. In New World myth and art, the underworld, the world of the dead, was one of the most important themes. Bat imagery was common because bats share several themes in the underworld, such as they are active in the dark, and they roost in caves, which were considered openings to the underworld. Vampire bats specifically were also part of folklore for the Mayans, who revered a vampire bat god. "Camazotz," the death bat, killed dying men on their way to the center of the Earth. Hieroglyphics and graphic drawings of the vampire bat are found throughout the Maya ruins in southern Mexico, Guatemala, and Honduras.

CONSERVATION STATUS

Out of the seventy-one listed species, the 2003 IUCN Red List categorizes four species as Endangered (facing a very high risk of extinction, or dying out, in the wild) and twenty-five species as Vulnerable (facing a high risk of extinction in the wild).

CALIFORNIA LEAF-NOSED BAT (Macrotus californicus): SPECIES ACCOUNTS

Physical characteristics: California leaf-nosed bats are small to medium sized, with a head and body length combined of 2.1 to 2.5 inches (5.3 to 6.4 centimeters). They have a visible tail that ranges from 1.4 to 1.6 inches (3.5 to 4.1 centimeters). These bats have a large noseleaf, large ears, and broad wings. Their fur is brown or gray. The underside is lighter, typically a brown or tan color.

Geographic range: California leaf-nosed bats are one of only a few species of this family found in the United States. These bats are found in southern California and Arizona, as well as northwestern Mexico. There is also a record of the bat being found in Texas.

Habitat: California leaf-nosed bats live in arid (extremely dry) habitats. They roost in caves, mines, and abandoned buildings. They often roost in well-lit areas. They select mines and caves that stay warm in the winter months due to the heat from the Earth.

Diet: These bats eat insects, such as crickets, moths, beetles, and a variety of other arthropods.

Behavior and reproduction: California leafnosed bats gather in colonies of hundreds to thousands. Smaller groups have also been found.

To locate prey, California leaf-nosed bats use both echolocation and the sounds made by the prey. They also can use vision to find prey, and when they do, they stop producing echolocation calls. They capture their prey both while flying and from gleaning, picking the prey off surfaces such as vegetation and the ground. After they catch it, they take the prey to a roost to eat. They only eat certain parts of the prey, dropping legs, wings, and other parts of the insect on the ground.

These bats mate in August, September, and October. Males attract females by flapping their wings and vocal sounds. Females form maternity colonies, and the female has one offspring the following spring.

California leaf-nosed bats and people: The disturbance of these bats' natural habitats through mining has caused a decrease in these bats' population.

Conservation status: The California leaf-nosed bat is listed as Vulnerable. ∎

VAMPIRE BAT (Desmodus rotundus): SPECIES ACCOUNTS

Physical characteristics: Vampire bats have a combined head and body length of about 2.7 to 3.7 inches (6.8 to 9.3 centimeters). One of these bats' striking features is their pointed front teeth. These bats have dark grayish brown fur, which is lighter on the underside. Ears are pointy and there is no visible tail. The thumb is clawed. Females are generally larger than males.

Geographic range: Vampire bats are found in northern Mexico to central Chile, Argentina, Uruguay, and Trinidad.

Habitat: Vampire bats live in warm climates, in both tropical and subtropical (nearly tropical, with warm temperatures and little rainfall) areas. They are commonly found where there is plenty of livestock. These bats are found roosting in caves, mines, tree hollows, and occasionally abandoned buildings.

Diet: Vampire bats feed on blood. These bats need about 2 tablespoons (29.6 milliliters) of blood each day; this is about 60 percent of the bat's body weight. Bats need to feed nightly.

Behavior and reproduction: Vampire bats are social animals; they roost in colonies that can range from twenty to 100 individuals. Much larger colonies of thousands have also been found.

Vampire bats approach their intended food source stealthily. They can walk, run, and hop along the ground, using their strong hind limbs and thumbs. At night, when vampire bats emerge to hunt for food, their victims are often sleeping. The bat will land beside the sleeping animal and then climb up until it finds a feeding spot. With its sharp front incisor teeth, the bat pierces the animal's skin and laps up blood from the wound. Vampire bats have chemicals in their saliva that stops blood from clotting. The bite rarely wakes a sleeping victim.

These bats occasionally will share the blood with other bats from its colony. After one female grooms another, the female being groomed may regurgitate (re-GER-jih-tate; throw up) part of her blood meal for the grooming female. It is also common to see females regurgitate food for their offspring.

Vampire bats mate year round. Females typically give birth to one offspring in April to May, or October to November. The offspring remain with their mothers for several months after they are weaned. They often share blood from the same wounds with their mothers.

Vampire bats and people: The fact that these bats feed on blood, combined with mythological stories about vampires, has caused many people to fear all bats. While the fears are largely myths, vampire bats can transmit rabies to humans and animals. These bats have caused tens of millions of dollars of damage to livestock farmers by transmitting rabies. They are considered pests in many livestock areas where they live. Also, researchers are investigating the anti-clotting properties of these bats' saliva to help with people who have strokes, in which a blood clot in the bloodstream cuts off blood supply to a part of the brain.

Conservation status: In areas with lots of livestock, vampire bats flourish. These are not considered threatened animals. ∎

PALLAS'S LONG-TONGUED BAT (Glossophaga soricina): SPECIES ACCOUNTS

Physical characteristics: Pallas's long-tongued bat is named for its most distinctive feature: its long tongue. It is a relatively small bat, with a head and body length combined of 1.8 to 2.3 inches (4.5 to 5.9 centimeters). Its visible tail is short, only about a quarter of an inch (0.6 centimeters). Fur color is dark brown to reddish brown, and the underside is paler. These bats have a long, narrow snout, small eyes, and short, rounded ears.

Geographic range: Pallas's long-tongued bats are found in northern Mexico, Paraguay, northern Argentina, Trinidad, Grenada, and Jamaica.

Habitat: These bats live in lowland habitats. They are more commonly found in dry forests than in wet forests. Bats roost in a variety of sites, including caves, hollows in trees, mines, and abandoned houses.

Diet: Pallas's long-tongued bats feed on nectar, pollen, and insects. When those foods are scarce, they will eat fruit as well.

Behavior and reproduction: Pallas's long-tongued bats often share their roosting sites with other species. They are social animals, forming colonies of several hundred individuals to a few thousand. Smaller colonies have also been found. The bats use their long, narrow tongues to lap nectar from plants. Individuals forage for food independently.

Females give birth to a single offspring twice each year. Females form maternity colonies. The seasons of birth vary depending upon where the bats live. In Costa Rica, births occur in December to February, then in April to June.

Pallas's long-tongued bat and people: Pallas's long-tongued bats are important to the ecosystem because of their role in dispersing seeds as well as pollinating night-blooming cacti (KACK-tie or KACK-tee; plural of cactus) and many other species of plants.

Conservation status: These bats are not threatened. ∎

WHITE BAT (Ectophylla alba): SPECIES ACCOUNTS

Physical characteristics: These bats are relatively small, with a combined head and body length of 1.6 to 1.9 inches (4 to 4.7 centimeters). They are named for the color of their fur. The hair over their entire body is white to a light gray tinge. A ring of dark gray hair surrounds the eyes. Ears and noseleaf are yellow.

Geographic range: White bats are found from eastern Honduras to western Panama.

Habitat: White bats live in moist or wet tropical forests. They roost in makeshift tents about 6.5 feet (2 meters) above the ground.

Diet: White bats eat figs and other fruits.

Behavior and reproduction: White bats modify leaves of plants in the relatively low-growing plants of forests to make roosts. These bats chew the large leaves, nipping the center so that the two sides of the leaf fold downward to form a "tent," under which the bats gather. The bats have been found roosting singly and in groups of two, four, and six.

White bat females apparently bear only a single young. In Costa Rica, females give birth in April. The males were observed sharing a tent with females until the young were born.

White bats and people: There is no known connection between white bats and people.

Conservation status: The IUCN Red List categorizes the white bat as Near Threatened, or close to becoming threatened. ∎

FOR MORE INFORMATION

Books:

Fenton, M. Brock. Bats. New York: Checkmark Press, 2001.

Fenton, M. Brock. The Bat: Wings in the Night Sky. Buffalo, NY: Firefly Books, 1998.

Raabe, Emily. Vampire Bats. New York: Powerkids Press, 2003.

Ruff, Sue, and Don E. Wilson. Bats. New York: Benchmark Books, 2001.

Schober, Wilfried, and Eckard Grimmberger. The Bats of Europe and North America. Neptune City, NJ: T.F.H. Publications, Inc., 1997.

Periodicals:

Clayton, Julie. "Wanted: Bloodsuckers; After Millions of Years of Bloody Enmity, Humans are Turning to Leeches, Ticks and Vampire Bats for Help. Julie Clayton Meets Our New Medical Allies." New Scientist (July 13, 2001): 42.

"Discovering Bats Beyond the Belfry." Business Times (November 9, 2001).

Seppa, N. "Compound in Bat Saliva May Aid Stroke Patients." Science News (January 18, 2003): 37.

"Stroke Patients get Vampire's Kiss." Current Science (April 11, 2003): 13.

"Vampire Bats Don't Learn From Bad Lunch." Science News (March 15, 2003): 173.

Web sites:

"The Secret Life of Bats." Fathom. http://www.fathom.com/course/21701775/session5.html (accessed on June 21, 2004).

Tomlinson, Denise. "Natural History of the Vampire Bat." The Organization for Bat Conservation at Cranbrook Institute of Science. http://www.batconservation.org/content/meetourbats/vampire.htm (accessed on June 21, 2004).

"Phyllostomidae." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Phyllostomidae.html (accessed on June 21, 2004).

"Vampire Bats." NationalGeographic.com. http://www.nationalgeographic.com/kids/creature_feature/0110/vampirebats.html (accessed on June 21, 2004).