Washington D.C. Bats
Before you get too upset about the bats in your house, open your mind to the following facts: bats are the only flying mammal in the world, and bats are very beneficial in that they can eat over 500 flying insects per hour all night long. Over 40 species of bats live in North America - and there's not a vampire among them! Bats need a safe place to roost in the daytime and much of their natural habitat is dwindling. While they do get into occupied dwellings, there is a safe, effective, and responsible way to deal with the problem.
Like other mammals, a very small percentage of bats contract rabies (figures issued by health departments may show a higher percentage since sick bats are easier to catch than healthy bats). Exposure to the rabies virus is remote if contact with bats is avoided and pets are properly vaccinated.
Histoplasmosis is an airborne fungus disease that can grow in pigeon and bat droppings (guano), but usually the guano must have contact with moist soil, which is normally not present in a dry attic environment.
Human inhalation is usually the result of stirring up dust that contains contaminated fungus spores, therefore it is not recommended to clean up bat guano unless there is a serious odor or health problem. Bat guano should only be cleaned up by trained personnel with the proper safety equipment.
Bats are host to ectoparasites such as bat bugs (a close relative of the bed bug). Fortunately ectoparasites associated with bats are usually host specific, and rarely bite pets or humans. Ectoparasites can be controlled by an insecticide treatment to the roost after the bats are evicted.
Humans object to the bat's noise (squeaking, scratching, crawling in attics and walls), stains, and odors caused by urine and droppings. Most bat complaints occur in July and August when bats enter houses via overhangs, eaves, unscreened vents, end construction gaps. Bats can squeeze through holes 3/8" wide (a dime sized hole). They occasionally enter the house through chimneys and open windows, and many actually get lost and enter the building interior after migrating through the structure to seek a preferred temperature zone.
Biology and Habits of House Bats
Bats are nocturnal (active at night) and have a 6 - 12" wingspan. They are insectivores (eat insects), and some species eat up to half their body weights each night in flying insects. Bats usually breed in fall or winter. Pregnant females congregate in maternity colonies until birth occurs between April and July. There are usually 1- 2 young that begin flying at 3 - 5 weeks of age.
Large colonies are usually found in caves and mines, while bats that live in trees are solitary. These bats are not normally found in structures, although a few species of bats will enter buildings to roost. Little brown bats commonly invade structures in the spring and summer, while big brown bats use buildings year-round for raising young and hibernation. Mexican free-tailed bats and pallid bats occasionallyenter structures and are found primarily in the Southwest U.S.
Individual bats that get into the living space of a house can often be let out by opening the doors and/or windows. Exclusion is the number one priority in bat management. Thorough exclusion of all holes larger than 1/4" is needed at all potential openings, especially in the top half of the building, and bat control should be left up to professionals. Contact the professionals at your local Critter Control office for further information on bat removal and control.
Poisoning bats is illegal and usually leads to an increased number of contacts with people and pets in the vicinity. Repellents are generally ineffective against bats and may even drive bats further into the structure.
Bats, despite their obvious value, are unjustifiably persecuted. Public education on bat conservation and responsible bat control methods are needed. Check to see if the local Critter Control office offers installation of bat houses to keep the bats around after they are evicted from inside the structure.
For further information on bat removal call Bat Conservation International at (512) 327-9721. We recommend reading "America's Neighborhood Bats" by Dr. Merlin Tuttle for information on how to live in harmony with these winged wonders.