BULLDOG BATS: Noctilionidae

PHYSICAL CHARACTERISTICS

Bulldog bats' lips are similar in appearance to a bulldog's. The lips are thick and the upper one hangs over the bottom lip, forming pouches. Their upper lip is split in the middle. The nose, which sticks out slightly over the lip, is long and thick. The ears are pointed and relatively large. Both species have long legs, and large feet with well-developed claws. The bats have long, narrow wings. They also have a visible tail. Bulldog bats have a strong odor, often described as fishy.

Bulldog bats are relatively large bats, having a combined head and body length that ranges from approximately 2.2 to 5.2 inches (5.7 to 13.2 centimeters). Males are larger than females.

Bulldog bat fur is typically short and slightly curly. Fur colors range from bright orange to orange-brown and gray-brown. There can be a pale stripe running down their backs. The undersides of these bats are lighter in color. At one point researchers thought that male bulldog bats were different in color than females. Males were said to be bright yellow, brown, and orange, and females a brown or gray color. Research has shown that fur color may vary among the species as a whole, and is not necessarily distinct between the sexes.

GEOGRAPHIC RANGE

Bulldog bats are found in Mexico, Central America, and South America as far south as Argentina. The greater bulldog bat also lives on islands in the West Indies.

HABITAT

Bulldog bats are found living near water and in other moist habitats. Greater bulldog bats generally roost, settle or rest, in dark caves, often located on the seashore, and the hollows of trees. Lesser bulldog bats roost in hollow trees, and in buildings.

DIET

Both species of bulldog bats eat insects, but greater bulldog bats feed primarily on fish, along with frogs and crustaceans, freshwater and saltwater animals with no backbone, such as shrimp. The greater bulldog bat is one of only a handful of bats known to eat fish. Lesser bulldog bats feed primarily on insects.

BEHAVIOR AND REPRODUCTION

Like all bats, bulldog bats rest during the day. While bulldog bats may sometimes leave their roost in the late afternoon, they are most likely to begin foraging for food at dusk, sunset. Both species catch their prey, animals hunted for food, using echolocation (eck-oh-loh-KAY-shun), the technique of detecting objects from calling out sounds and listening to the echo reflected from the object. These bats use echolocation to detect prey in flight, on the surface of the water, or directly below the water's surface.

After bulldog bats catch their prey they either eat the insect in flight or tuck away the partially-chewed food in their cheeks. These bats have pouches in their cheeks that can stretch to hold extra food. By storing the food, bulldog bats do not have to return to their roost after each catch. Mother and father bulldog bats can store food in their cheeks to bring to their young.

Bulldog bats are found living in colonies or groups of about thirty individuals up to several hundred. One kind of colony has young male bats. Another type of colony is made up of males, females, and their young. When they begin foraging for food, groups of up to fifteen leave their colony at the same time.

FLYING WITH BIRDS

Look closely at a group of pelicans during the day and you might spot a few greater bulldog bats, or fisherman bats, in their midst. While these bats generally feed at dusk and during the night, observers have also seen them in the late afternoon flying alongside pelicans over water. Pelicans are large aquatic birds that eat fish. The bats probably catch small fish disturbed by the pelicans.

Female bulldog bats generally give birth to one offspring once a year. In general, bulldog bats mate in November and December, and then give birth in April through June. Births have also been recorded in the fall. The newborns can fly and become independent after one month. Both the male and female look after the baby, an unusual behavior for bats.

BULLDOG BATS AND PEOPLE

Bulldog bats eat insects that many people may consider pests. Water pollutants and habitat destruction are likely to harm the population of bulldog bats.

CONSERVATION STATUS

Bulldog bat species are not listed as threatened.

GREATER BULLDOG BAT (Noctilio leporinus): SPECIES ACCOUNT

Physical characteristics: The greater bulldog bat, also called the fishing bat, is a relatively large bat. These bats have a wingspan of almost three feet (1 meter), and a combined head and body length ranging from 4.6 to 5 inches (11.9 to 12.7 centimeters) Males are larger than females. Their feet and claws are much larger than the lesser bulldog bats, and their claws are very sharp. The fur is short and repels water.

Geographic range: Greater bulldog bats are found in parts of Central and South America, and throughout many islands on the Caribbean.

Habitat: Greater bulldog bats live in lowland and moist habitats that are near a water source, including the seashore, lakes, river basins, and ponds.

Diet: Greater bulldog bats eat primarily fish. They also eat crab and insects, including winged ants, crickets, and scarab beetles.

Behavior and reproduction: Greater bulldog bats typically roost in caves near a water source and in tree hollows. They roost in colonies of up to several hundred individuals bats. Each colony may have a distinctive odor. They emerge at dusk to forage for food in groups of five to fifteen.

Greater bulldog bats use echolocation to detect the ripples along the water's surface, which indicates a fish swimming. Groups of these bats zigzag low over the water and send out chirpy echolocation calls. The bats can track fish movement by predicting their speed and direction. Then they drag their sharp claws through the ripples and snatch the fish with their large, sharp claws. Once out of the water, the fish is carried to a perch, where the bat eats it. Greater bulldog bats may also capture insects and crustaceans on the surface of the water. Prey is either eaten in flight, stored in its cheeks, or carried to a roost to be eaten.

These bats have powerful wings. If they drop into the water while they are foraging they can use their wings like paddles. Once they have gained enough speed in the water the bat lifts itself up into flight.

Female greater bulldog bats generally have a single offspring each year. The breeding season may vary regionally. In the Northern Hemisphere, mating typically begin in November and the young are born in May and June.

Greater bulldog bats and people: The health of a population of greater bulldog bats may act as an indication of water pollution.

Conservation status: Greater bulldog bats are not listed as 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.

Nowak, Ronald M. "Bulldog Bats, or Fisherman Bats." Walker's Mammals of the World 5.1 Online. Baltimore: Johns Hopkins University Press, 1997. http://www.press.jhu.edu/books/walkers_mammals_of_the_world/chiroptera/chiroptera.noctilionidae.noctilio.html (accessed on June 22, 2004).

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

Richardson, Phil. Bats. London: Whittet Books, 1985.

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:

Pennisi, Elizabeth. "Gone Batty: Illuminating the Murky World of Tropical Bats." Science News (April 30, 1994): 284.

Schnitzler, Hans-Ulrich, and Elisabeth K. V. Kalko. "Echolocation by Insect-Eating Bats." BioScience (July 2001): 557.

Web sites:

Myers, P. "Noctilionidae." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Noctilionidae.html (accessed on June 22, 2004).

Pederson, Scott. "Bulldog or Fisherman Bat: Noctilio leporinus." Bathead. http://biomicro.sdstate.edu/pederses/guidenlep.html (accessed on June 22, 2004).

Simmons, Nancy. "Noctilio albiventris minor, Lesser Bulldog Bat." DigiMorph. http://digimorph.org/specimens/Noctilio_albiventris/whole (accessed on June 22, 2004).