|Arizona is home to 28 species of bats, more than almost any other state. Bats are the only true flying mammals and are valuable human allies. Worldwide, they are primary predators of vast numbers of insect pests, saving farmers and foresters billions of dollars annually and helping to control insect-spread human diseases. For example, large colonies of Mexican free-tailed bats (Tadarida brasiliensis) eat hundreds of tons of moths each week, especially the moths that prey on cotton crops.
Although bats play key roles in keeping insect populations in balance, they are North America's most rapidly declining land mammals. Declines are often caused by human fear and persecution, and each of us can help by learning how to live with these animals.
Description and Habits
- Fist-sized or smaller, with short fur and thin wings, many have large ears
- Brown, gray, yellow, red, some with frost-tipped fur, spots or dark eye mask
- Similar eyesight to humans
- Many eat insects in flight and can eat more than 1,000 insects in an hour, including mosquitoes
- Some species drink nectar and can drain a hummingbird feeder overnight
- Use echolocation, emitting sound to locate solid objects
- Hang upside-down to rest in dark, secluded “roosts” during daytime; leave roost to forage for food at night and may temporarily roost to digest food and groom
- Some hibernate during winter (October through April), and some stay active year-round
- Most have one or two live young each year, usually between May and July
- Females nurse offspring and form maternity roosts that can contain hundreds or thousands of bats
Potential Conflicts with Humans and Pets
While some people appreciate bats and the ways they benefit us, others fear bats because a small percentage of them can expose humans and pets to rabies. Bats should always be kept out of places where people live indoors. Bat guano (feces) can present disease and odor problems. However, bats are generally harmless to humans and are extremely beneficial for controlling insects and mosquitoes and pollinating some plants. Bats are vulnerable to disturbances by people because of their roosting habits and slow reproductive rate.
What Attracts Them?
If bats are in an area, it is probably because they are finding food, water or shelter.
- Food can include insects that congregate in areas near lights, agricultural or playing fields, ponds or other water sources. Nectar-feeding bats may be attracted to flowering agaves and hummingbird feeders.
- Water sources can include any pool, pond or lake with a long flying corridor that bats can skim.
- Shelter can include rough surfaces for hanging. A bump of only 1/16 inch is enough. Bats can squeeze into holes as small as 3/8 inch and are attracted to spaces inside buildings and attics, under bridges, in culverts, behind siding on buildings, in palm trees, and under eaves and porch or patio awnings.
Bats should never be allowed to remain in human living areas. However, bats roosting on the porch, in the yard, or in a bat house are far more beneficial than harmful, and the small amount of guano can be cleaned up or used as fertilizer, in exchange for the reduction in flying insects and mosquitoes. The following ideas can help you coexist with bats or exclude them if necessary.
In an emergency:
- If a person or pet is bitten by a bat, immediately wash the wound, attempt to capture the animal while wearing leather gloves, and contact your local county health department right away. The bat may have rabies and must be tested to determine whether the bite victim needs rabies shots.
- If a bat is in human possession, please call your local Arizona Game and Fish Department regional office during weekday business hours. After hours and weekends, call the Arizona Game and Fish Department radio dispatcher at (623) 236-7201.
Solutions to common problems:
A bat inside a building is probably just lost.
- Close the interior doors to confine the animal to one room or section of the building (making sure all pets and children are out of the area).
- After dark, open all doors and windows to let the bat fly outside on its own.
- Turn inside lights off to help bats find open windows and doors.
- If the bat does not leave on its own after several hours, put on leather gloves, and then place a box, coffee can or glass jar over the bat when it is on a wall. Slide a lid or piece of stiff paper over the top; then release the bat outside while it is still dark.
- Hold the bat up high to allow it to fly away, or place it on the edge of a tall building, fence or tree branch (otherwise it may not be able to fly up from the ground).
- Handle bats gently to avoid injury to the bat, and never handle bats with your bare hands.
- If a bat cannot leave an indoor space on its own or be let out easily, please call a wildlife control business.
- Bat on a building during the day
Migrating bats may roost temporarily as they move through an area. This happens most often during spring and fall. Bats roost in cracks, crevices, beams or holes.
- These bats will usually only be around for a few days, or maybe up to a week or so, and it is best to leave them alone.
- After the bats move on, seal cracks or holes with foam, weather stripping or other materials if desired.
- Never exclude bats between May and September unless you are sure no young are left behind.
- Young bats are left alone all night while their mothers search for food and should not be disturbed. If the mothers do not appear by daylight, contact either the Arizona Game and Fish Department Wildlife Center at Adobe Mountain at (623) 582-9806 or a licensed wildlife rehabilitator.
- Bat on a building at night
Bats roosting during the night are generally digesting insects caught nearby and will leave within a few hours. “Night roosting” bats are attracted to porches, patios and overhangs.
- Clean up the guano during the day, and then check the area the next morning to find out if the bats are indeed night roosting or if a day roost is present.
- Guano makes an excellent garden fertilizer; place sand beneath the roost to make cleanup easier.
- Discourage unwanted night-roosting bats by:
- Changing temperature - leave a light on in the area during the night;
- Changing humidity - leave a fan on overnight to blow air directly toward the bat roost site;
- Tying mylar balloons so they bump against the roosting area;
- Covering wood, stucco or problem areas with metal or plastic sheeting.
- Bat on the ground
A bat on the ground that acts sick or unable to move may have rabies.
- If a bat is on the ground and sick or unable to move, then leave it alone, keep pets and children away, and contact your local county health department immediately.
- Most bats cannot fly up from ground level. If a bat has been knocked down during a storm and does not seem sick or injured, then use a stick to gently raise it to a tree limb. At nightfall, the bat should fly away.
- If a bat is injured or a baby bat is on the ground, then contact the local Arizona Game and Fish Department office for instructions. NEVER handle a bat with bare hands.
At least seven species of bats roost in crevices under some bridges in Arizona.
- Contact your local Arizona Game and Fish Department office or e-mail the Bat Project at email@example.com for advice before maintaining or removing a bridge.
Remember, removal is usually a last resort:
Bats are protected by state law, and disturbing a colony of bats where babies are present can result in dead bats and large fines. Bats reproduce slowly compared to other small mammals, and their benefits usually outweigh any harm they might cause. Bats should never be allowed to remain inside human living areas, but bats outside can be tolerated and even encouraged.
To prevent further problems:
- Remove bug lights and water sources, and turn off outside lights at night to avoid attracting bats.
- Bat-proof your home – This is the safest, most permanent way of keeping out unwanted bats:
- Consider allowing the bats to remain if they are not inside the living quarters of the house or causing property damage.
- Never exclude bats during the summer months (May to September). This is the maternity period, when bats leave their young in the roost to forage for food, and young bats could be trapped inside and separated from their mothers.
- Find entry and exit points.
- If you cannot see into the opening to determine whether all bats are gone, then hang lightweight wire screening or hardware cloth over the entry and exit holes, attaching it on the top and sides, but leave the bottom loose and open. Bats inside can crawl out, but will not be able to re-enter.
- Wait a few days (or weeksduring winter when bats are less active) to allow all of the bats to leave. Then, permanently cover the entry hole with lightweight wire screening, metal sheeting or hardware cloth.
- When all animals are gone, and well after darkness has fallen, patch up entryways (remember, bats can squeeze though openings as small as 3/8 inch).
- For help or advice with excluding bats from your house or property, please contact a wildlife control business.
- Install one or more bat houses on your property as an alternative for bats roosting in your buildings. Plans are available online at batcon.org, or check with your local Arizona Game and Fish Department office to see if free bat houses are available. You can even monitor your bat house (click the link for “Research Data Form”) to help the department learn the best techniques for making bat houses most effective in Arizona.
Possible Health Concerns:
- Rabies - Bats are one of the known rabies vector species in Arizona, although less than 1 percent of wild bats are likely to have rabies at any given time. Symptoms of a rabid bat include inability to fly, flying during daylight, lethargy and paralysis. Most bats, even if sick, will not attack a person, but bats may bite if handled. If a live bat is on or near the ground, then leave it alone, keep pets and children away, and contact the local county health or animal control agency. Anyone bitten by a bat should immediately seek medical attention. If possible, the bat responsible for the bite should be captured and tested for rabies.
- Histoplasmosis – This disease is caused by a fungus (Histoplasma capsulatum) that lives in soil enriched by bird or bat droppings. The fungus is rare in dry Western climates, although it has been found in Arizona. It could be present in dry, hot attics of buildings. Infection is caused by inhalation of airborne spores in dust enriched by animal droppings. The vast majority of histoplasmosis cases in humans is asymptomatic or results in only flu-like symptoms, though a few individuals may become seriously ill, especially if exposed to large quantities of spore-laden dust. The disease can be avoided by not breathing dust suspected of being enriched by animal feces. (Text from Bat Conservation International Web site.)
Laws and Policies
- All bats in Arizona are protected and cannot be collected or killed. Proper exclusions may be performed where necessary.
- It is unlawful to use pesticides or other chemicals directly on bats.
- Bat exclusions should be done only with the advice of the Arizona Game and Fish Department or a wildlife control business, and should not be attempted during the maternity season (generally May through September) to avoid separating mothers from their young.