The BAT-PATROL

Enlarge Image Image Gallery

Build a better bat house, and you can say goodnight to summer mosquitoes.

By Rob Miles

Even the most stalwart outdoorsperson might feel a chill when encountering a bat swooping around the yard at dusk. Perhaps it's a natural reaction to fear flying things we can't see well, or maybe we're conditioned by lore and legend to abhor these furry fliers. In either case, bats share the floor with spiders when it comes to inspiring unwarranted fear.

Bats' nocturnal nature has made them a poor subject for study in the past, but a great deal of progress as been made in the last 20 years in researching the nearly 1,000 different varieties. It's clear to many people now that bats play an important role in nature and are largely beneficial to humans around the world - their appetite for insects being only one of the services they provide.

Like birds, bats play a critical role in seed dispersal. For example, fruit bats living in the tropics excrete seeds from the ripe fruit they eat. They do this in flight, often a considerable distance from the parent tree. The seeds, packed into their own fertilizer (See Guano Basics ), then grow into new fruit trees, regenerating the vulnerable rainforests. Some bats also drink nectar from flowers and - like hummingbirds, bees, and butterflies - pollinate the flowers. The saguaro and organ-pipe cactuses, which grow in the southwestern United States, depend on long-tongued bats for their pollination and survival. The cactuses, as nocturnal as the bats, flower only at night, and their configurations make it impossible for any creature but bats to access the nectar.

The most obvious contribution bats make to hu mans is their unparalleled insect consumption. Many bats, and almost all in the United States, thrive on an insect diet. A bat can eat up to 1,200 mosquito-sized insects every hour, and each bat usually eats 6,000 to 8,000 insects each night.

Their appetite for mosquitoes certainly makes a back yard more comfortable. Bats are opportunistic, and their lack of discretion benefits everyone. Some of their favorite prey include crop-destroying moths, cucumber beetles, flies, and gnats.

Unfortunately, about 40 percent of bat populations worldwide are in danger of going extinct. Several characteristics of bats cause them to be vulnerable. First, they are slow at reproducing. Most give birth to only one pup a year, which means they cannot quickly rebuild their populations. Second, most bats roost in large colonies. Bats living in temperate climate zones hibernate in caves or mines during the winter. During the summer, maternity roosts can house several million female bats and their offspring. Like putting all of your eggs in one basket, putting all your bats in one cave can result in disaster if the shelter is disturbed or destroyed.