Bats are Your Friends - February 28, 2007
Jeff Schalau, Associate Agent, Agriculture & Natural Resources, Arizona Cooperative Extension, Yavapai County

Over the years, bats have been stigmatized by folklore and misinformation. It is not their goal in life to be tangled in your hair, suck your blood or give you rabies. They simply want to go about their business of feeding, roosting, and reproducing in the areas they have grown accustomed to over generations. There are 986 species of bats worldwide and in each case, they are key members of the ecosystems they live in. They are also interesting to scientists because they are the only mammals that can truly fly.

So, why are we discussing bats in a gardening column? Well, to put it bluntly, they help humans in ways we are only beginning to comprehend. Bats eat insects, pollinate plants, and disperse seeds. Most Arizona bats are insectivorous: eating mosquitoes, beetles, flying ants, roaches, moths, centipedes, crickets, grasshoppers, cicadas, and other insects that humans consider pests.

Some bat colonies in Texas have 20 million individuals, and consume 100,000 pounds of insects nightly. A few Arizona species feed on pollen and nectar of agave, saguaro, organ pipe, and other cactuses. This feeding behavior not only benefits the bats, but cross pollinates the flowers, which in turn, diversifies the gene pools of these plants. Many bats are known to feed on nectar, fruit, pollen, and insects. In recent years, scientists have learned much about bat habitat requirements and feeding habits of many 27 Arizona bat species.

Roosting habits most often trigger bat/human conflicts. Bats use structures to roost because they supply openings where bats can safely hide from predators and a favorable environment. Since bats do benefit us, we should try to respect them. They are only seasonal visitors to our area. Much information is available on safely excluding bats from attics, eaves, and crevices of houses. Bats can be excluded from chimneys and vents with half inch hardware cloth. Bats can potentially enter through a 3/4 inch diameter hole or an opening 3/8 inch by 7/8 inch. These entry points can be caulked with silicone, stuffed with steel wool, or simply taped.

Bat exclusion should not be attempted when flightless young are present (usually June or July). Bats usually have one (sometimes two) young per year. Unlike rodents they rely on a long lifespan maximize their reproductive potential rather than large litter sizes. If you decide to exclude them from one area, you can provide another area for them to roost: a bat house. These structures are commonly wooden boxes with one to three chambers inside where bats can enter and safely roost. The chambers have a restricted opening to allow bats to enter. Bat houses also have gaps between boards to provide ventilation. Many designs are available for purchase preassembled or as kits.

Bat colonies in attics and bat houses attached to houses can also create some health issues. Bat bugs are small insects related to bed bugs that live in conjunction with bats and other nesting birds such as feral pigeons and swallows. These insects are blood feeders that prefer bats and birds as their hosts. When the bats or birds leave or die, the bat bugs invade living areas through cracks and crevices. Bed bugs and bat bugs also may come from other infested homes by way of water pipes, gutters, through windows, along walls, etc. The bite of these bugs often is painless, but toxic saliva injected during feeding will later cause severe itching and an inflamed welt. If you suspect bat bugs or bed bugs, capture some samples and bring them to your local Cooperative Extension office.

Many people are concerned that rabies is transmitted by bats. Rabies is an infectious viral disease that invades the central nervous system of humans and other warm blooded animals. Most often it is noticed in dogs, cats, foxes, raccoons, skunks, coyotes, bats, and livestock. Worldwide, 30,000 fatal human rabies cases occur per year. Ninety-nine percent of these are from dogs. However, any bat moving slowly enough that you could catch is very likely sick. Contact Arizona Game and Fish or Yavapai County Animal Control if you find such an animal.

The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site:

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: July 16, 2009
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