The Evironmentally Protective Night Creatures
by Timothy Roseth, edited by Katherine Roseth
Do you, or those you love, get the heebie-jeebies whenever you think of bats and other creepy crawlers? Learn how bats play an important role in protecting our environment and our gardens, and pass it on to your friends.
Environmental Impact
Bats play a critical role in maintaining a healthy environment. They are primary predators of night-flying insects and valuable seed dispensers. The little brown can consume several hundred mosquitoes in an hour. The misconception that bats get tangled in people's hair is more likely to be a bat pursuing a mosquito that's pursuing you. A colony of 150 big brown bats can protect farmers from hundreds of thousands of crop destroying insects in one summer. A colony of 20 million Mexican Free-Tailed bats in Bracken Cave, Texas consumes over 200 tons of insects per night. Farmers would have to rely on pesticides to combat crop-destroying insects without this consumption. Approximately 70% of bats are insect eaters. Some bats eat fish, rodents, small reptiles and amphibians.
Many of the old-world tropic bats consume fruit, filling a vital role of pollinating night flowering plants and seed dispersion. Seeds dropped by bats in tropical regions account for 95% of forest regrowth in cleared lands. Only three, of the 100 varieties of bats, live on fresh blood. Known as the vampire bat, these Latin American dwellers will take a tiny bite from a sleeping animal or human. An anticoagulant present in the bat saliva keeps the blood flowing while the bat laps it up. Usually the host is unaware that it is providing the meal. Feeding on humans is relatively rare, and the anticoagulant has been synthesized and is now used to treat human heart patients.
Local Residents
Minnesota is home to several species of bats that share similar traits. Most Minnesota bats migrate to more hospitable climates during the winter although some species stay until November or December. Bats rely on echolocation to find insects and avoid predators. This involves creating sound waves with their mouths or noses and then forming a mental picture from the waves bounced back from the object. A bat's ability to hang upside down allows it to roost in places out of a predator's reach. It also allows it to drop right into flight. A specialized tendon holds its toes in place so it does not expend any energy to remain in this position.
The little brown bat is brown (obviously) or russet to gray in coloration with a wingspan of 222 mm to 315 mm. It is often found in roosts including abandoned mines, caves, tree hollows and buildings close to water where it can feed on aquatic insects. One little brown can eat up to 600 mosquitoes an hour.
Similar in appearance but much larger is the, appropriately named, big brown bat. It is brown to copper colored with a wingspan of 325 mm to 350 mm. It roosts in generally the same places as the little brown. It is one of the most commonly encountered bats. The big brown has a voracious appetite for beetles and is quite valuable as a pest controller for crops.
The red bat is medium-sized with a wingspan of 290 mm to 332 mm. It has angora-like fur and coloration varying from bright orange to yellowish brown. Because it usually roosts in the foliage of deciduous trees, encounters with humans are rare. Flying at up to 40 m.p.h., the red bat can pursue a wide variety of insects, particularly moths. It has been known to congregate around corncribs to feed on the emerging grain moths.
The hoary bat is one of largest and most commonly found in America. Its wingspan is 380 mm to 410 mm. Its thick, darkly colored fur is tipped with white giving it a frosted appearance. Like the red bat, the hoary bat roosts in trees, preferring evergreens. It is also a big consumer of moths (although it will not forgo dining on mosquitoes). It is the most likely bat to bite when grounded and should be left alone.
The silver-haired bat is usually black or dark brown with silver-tipped fur. Its wingspan is 270mm to 310mm. It prefers to live in crevices, such as under tree bark or tree hollows. It emerges early in the evening to feed over ponds and streams or forest clearings on a wide variety of insects.
Rabies
Bats, like all mammals, can carry the rabies virus. However, unlike dogs, bats rarely become aggressive. They do not contract the virus at a rate higher than other warm-blooded animals. The infected bat usually dies due to infection. If you come across a sick or wounded bat, do not handle it. It may bite in self-defense. Although 90 to 95% of sick bats do not have rabies, if you are bitten or scratched it's best to have the bat tested for the virus. Bat rabies accounts for approximately one human death a year in the U.S. If you wish to protect yourself and your family from rabies, you should really vaccinate your dog.Bat Houses
These gentle creatures are rapidly losing habitats due to persecution, vandalism, and human encroachment. Intrusions into caves during the winter have caused hibernation disturbances that led to the mass-starvation of thousands of bats. Although bats are long-lived for their size, some up to 30 years of age, bats are exceptionally vulnerable to extinction because females produce only one pup a year. Consider installing a bat house. Putting up a bat house will not increase the likelihood of bats moving into your attic, but rather they can be especially useful as an alternative home if bats have taken up residence in your house. Bats can usually be persuaded to move to another location that better meets their needs. If a pest control company's first response is to use chemicals to eradicate bats, find a more environmentally responsible company.
Generally, bats prefer to live within several hundred yards of water, however some bachelor colonies will live up to two miles away. Bat houses can be mounted on the side of a building, on a pole, or in a tree. The houses should be located in a clear to allow for takeoffs and landings. Also, it should not be placed in an area that would expose it to predators such as raccoons or snakes. For these reasons, trees are generally less desirable than poles or buildings. In northern climates, mount the house as high as you can, between 12 and 15 feet if possible. It's best to paint or stain the bat house dark brown or black, and have the house face south. This will allow it to maximize heat absorption.
For more information about the specific construction of bat houses, please contact Bat Conservation International.
References: Bats of the WorldAmerican Neighborhood Bats