BY TOM GILLESPIE

Special to The Pilot

It's likely that only snakes are more feared and more misunderstood than bats.

To help alleviate some of those fears and to help visitors better understand these unique nocturnal mammals, the North Carolina Zoo daily exhibits 15 common vampire bats in the park's Sonora Desert exhibit.

Vampire bats do not suck blood, but rather lap the blood at the site of the bleeding. They typically feed on the blood of domesticated animals such as cows, pigs and horses and require about two tablespoons of blood each day. Zoo visitors can view bat feedings and talk to the keepers at 3:30 p.m. each Saturday and Sunday and on holidays.

Bats are in the taxonomic order Chiroptera and have the same characteristics of most other mammals. Not surprisingly, the word Chiroptera comes from the Greek words cheir (meaning "hand") and pteron (meaning "wing"). It's hardly a stretch, considering that the bat's open wing is similar to an outspread human hand with a membrane between the fingers that also stretches between hand and body.

They give birth to live young (rather than laying eggs) and feed them with their milk. Bats' most distinguishing features are their forelimbs, which have developed as wings. This makes them the only mammal naturally capable of flight. Although some mammals, such as flying squirrels, might be erroneously thought of as fliers, they are actually gliders that can only travel limited distances through the air.

Present throughout most of the world, bats make up about 20 percent of all mammal species. The zoo's vampire bats are one of nearly 1,100 species worldwide. About 70 percent of all bat diets consist chiefly of insects and other small creatures, making them insectivores. A few species are carnivores (meat eaters), but most species are frugivores, feeding primarily or exclusively on fruits.

Bat colonies are well structured, with strong social bonds. They are often grooming each other and recognizing other colony bats with voice and smell. >Their social structure is imperative to their survival since hungry bats that have not found food that night or are forced to stay behind are sometimes fed from others through a process of regurgitation. >

Like snakes, bats help humans in many ways. In addition to pollinating flowers, bats also eat harmful insects. By some estimates, a single bat can consume as many as 1,200 mosquitoes per hour. Bat feces, called guano, is actually a strong natural fertilizer - so strong, in fact, that people who collect it often have to wear protective masks and clothing. Almost odorless, guano is also an ingredient in gunpowder because of its high levels of phosphorus and nitrogen.

Unfortunately, the cave mining of guano deposits can be deadly to the bat colonies themselves. In the wild, bats are highly vulnerable to disturbance to their roosts. Some species, especially those with low fat reserves, will starve to death when regularly disturbed and put into a panic state during their resting period. Many species will drop their young (called pups) when panicked, leading to further reductions in populations.

Common vampire bats (Desmodus rotundus), like those exhibited at the N.C. Zoo, are one of three species of bats that feed solely on blood, a dietary trait called hematophagy. All three species are native to North, South and Central America, ranging from the desert area of northern Mexico to Brazil, Chile and Argentina.

Compared with other bat species, vampire bats generally have a short tail membrane and small ears. Their front teeth are specialized for cutting, and their back teeth are much smaller than in other bats. Their digestive system is adapted to their liquid diet, and their saliva contains a substance called draculin. This saliva, a natural anticoagulant, is now being reproduced synthetically to help heart patients and has been an inspiration to researchers for stroke treatments.

Although vampire bats have been depicted in folklore and films as creepy blood-suckers, they are actually beneficial to man and nature and, like so many other animals thought to be nuisances, are a vital part of our ecosystem.

Tom Gillespie works for the public affairs office of the N.C. Zoo.