The bat species of North and South America, and their contribution to our environment including construction ideas for bat boxes and preferred habitat.
While walking to your car one warm summer evening you notice a tiny creature fluttering noiselessly in the night sky. You realize that it's a bat - should you (A) run away screaming to prevent it from becoming tangled in you hair or, (B) be grateful the bat is up there devouring those night-flying insects that can make you life miserable.
If you chose (B), then you were right on the mark!
Through the ages bats have acquired an undeservedly bad reputation, when in fact these fascinating creatures are an important part of our ecosystem. Contrary to popular belief, bats are not blind, they don't become tangled in human hair, and rarely transmit disease to other animals or humans - in fact, bats generally only bite when they are threatened or provoked and less than one-half of one percent of American bats contract rabies. Although we've all heard the old saying "blind as a bat" bats are actually not blind at all, they swoop and dive using a sophisticated combination of sight and echolocation for guidance.
Bats live in each of the fifty states and across the globe with the exception of the polar regions). Within the four families of bats living in the United States there are forty-five different species - each one performing a vital function within its own environment. Bats are one of the most important natural enemies of night-flying insects in the world. One North American "little brown bat" can devour as many as 1,200 mosquito sized insects in only an hour and the "Mexican free-tailed bats" of Bracken Cave, Texas are known to consume over a million tons of insects every night. However, insects are not always the chosen diet of bats. Some species of bats prefer to dine on centipedes, scorpions, or small fish, and some choose fruit or the nectar of tropical trees and flowers.
In Arizona, desert dwelling bats pollinate several species of giant cacti including the saguaro as they feed on the cactus nectar. Many tropical flowers and trees are pollinated, and their seeds dispersed through the distribution of bat guano; in fact, the seed production of the agave plant (the source of tequila) would decrease to one-three thousandth of it's normal rate without the assistance of nectar eating bats.
Although bats fly, they are not birds at all - but mammals. There are nearly 1,000 distinct types of bats which account for almost twenty-five percent of all species of mammals on earth. Bats generally produce only one offspring per year, and because of this slow reproductive rate, forty to fifty percent of the American bat population is in jeopardy of extinction. Bats are devoted to their families, sometimes risking their own lives by sharing food with orphaned youngsters in the same roost. A good example of "bat devotion" is the Mexican free-tailed bat. They raise their young in colonies numbering in the millions - and are still able to locate and nurse their own offspring among the several hundred bats clustered per each square foot of cave space.
Occasionally a family of bats may establish their roost in the attic of a home and although upsetting to the homeowner, bats are fairly easy to evict. In the evening watch closely around any suspected attic openings until you can determine where the bats are entering, then cover the opening with a piece of bird netting (available at garden centers). This will allow the bats to exit the attic, but not to return to their roost. Take care not to block out the adult bats during the time of year when they are raising their young (this information is available from your Department of Agriculture or county extension agent).
Installing a bat house near your home will establish an excellent natural pest control team and reduce your dependence on harmful chemicals used to control insect populations. Before you begin, there are a few rules to learn for successfully attracting a bat colony. Most bats prefer to live within one-half mile of a water source, and they also want their home located where it will receive 6 - 10 hours of sunlight each day (for warmth). Ideally the bat house should be mounted on a pole 15 to 20 feet above the ground (higher is better) in an area that has no branches of obstructions to flight. Bat houses mounted under eaves, in the shade, or nailed to tree trunks are usually colder, more susceptible to predators and less appealing to house-hunting bats.
A suitable bat house should be at least 2 feet tall and 14 or more inches wide with a roughened (or screen-covered) landing platform extending 3 to 6 inches below the house. Multi-chambered houses (3 - 4 chambers) are a good idea and will accommodate a larger family. The chambers should be 3/4 to 1-inch wide depending on the species of bat common to your region and can be constructed from 1 / 4 inch plywood, roughened or covered with 1/8 inch mesh HDPE (plastic) netting.
A Bottomless Bird House
The ideal bat box will include an exterior plywood front, back and top with 1" thick cedar sides (never use pressure treated wood). Caulk all seams, especially the roof, and screw the house together with all-purpose screws making sure no sharp points extend into the living quarters.
If mid-summer temperatures in your area rise to 85 F or above you should incorporate ventilation slots in the front and rear walls of the house to prevent overheating. Remember, bats like a temperature between 85 and 95 F during the warm summer months and can overheat without sufficient ventilation. Rear vents should be ½ inch wide by 6 inches high and spaced about six inches from the bottom of the house. The single front vent should extend from side to side about six inches above the bottom.
Complete the house with at least two coats of exterior paint. Black is most often used in colder climates since it absorbs heat but dark gray or even green are suitable colors in warmer climates.
When the bat box is securely mounted it may take some time for a bat to move in - - but be patient, and check the box occasionally to look for new arrivals and remove unwanted wasp nests. Reptiles are also a problem, and you might want to install a guard (available from bird house suppliers or garden centers) if climbing snakes live in your area.
Once a bat family moves into their new home, just sit back and enjoy watching one of our most under-appreciated neighbors!
