About Bats

There is nothing to fear from the presence of the only flying mammal in Massachusetts. Bats are intriguing mammals and expert pollinators and seed dispersers that seldom cause problems for humans and are very beneficial to have around. These highly social animals are nocturnal and use a type of natural sonar called echolocation to perform one of the most important ecosystem services of any animal: pest suppression. They are the primary predators of night-flying insects, including the disease-carrying insects we find in our backyards. They have a high metabolism so bats can eat up to 125% of their body weight in insects in a single night. Seventy percent of bat species worldwide are insectivores, and over 99% of bats found in the United States eat insects.

Did you know? Tequila is produced from agave plants, which rely on bats as their primary pollinators.

MassWildlife bat boxes

Throughout Massachusetts there are nine species of bats, five of which are considered endangered. Bats are among the slowest reproducing mammals based on their size, usually having only one pup each year. This, along with habitat destruction, pesticides, and climate change are threatening all species of bat. Currently, one of the greatest threats to bats in Massachusetts is White-nose Syndrome (WNS), a fungal disease that has caused devastating mortality of bats that spend their winters hibernating in caves and mines. Bat houses provide clean homes for bats that are free of white-nose syndrome. MassWildlife has launched a new initiative to install bat houses across the state. Artificial roost sites (like bat houses) are tools for mitigation, conservation, and habitat enhancements for sensitive bat species.

Like most wild animals, bats prefer to avoid contact with humans. But in situations where bats and humans come into close proximity, it is important to understand how to prevent negative outcomes for humans and bats.

POSSIBLE CONFLICTS & SOLUTIONS

Conflicts with bats usually involve either a bat accidentally entering living areas or bats roosting in buildings or homes. Bats typically roost in higher places, thus the term “bats in the belfry,” making the attic the most common place to find them. If you should accidentally encounter a bat, remain calm and remove children and pets from the area. Bats are not normally aggressive, and will try to avoid contact with humans and pets.

If you have found a single bat inside a house/structure and…

There has been no human contact:  Give the bat a way out and it will leave. If it is safe to do so, close all interior doors so that the bat is isolated in one area. Then, open all windows and doors leading to the outdoors in the area where the bat is located. When doing this, stay close to the walls because bats fly in u-shaped patterns, flying lower in the center of the room. Once the bat is out of the room, locate its access point and close it off.

There has been contact:  If it is safe to do so, close all interior doors so the bat is isolated in one area but do not open any windows or doors leading to the outdoors. Exit the structure immediately thereafter and call a local animal control officer or the board of health for assistance with catching the bat so that the bat can be tested for rabies. Do not attempt to catch the bat yourself! Follow up with your physician.

Contact is questionable: i.e., someone was sleeping/children or mentally challenged persons were present. The Centers for Disease Control recommends that if a bat is discovered in a room with a sleeping person, it should be captured by local or state authorities and submitted for rabies testing because a bite can be so insignificant it can be overlooked. Follow contact instructions above.

Bats often enter rooms through an open window or door, but they can also enter through places like chimneys, openings in interior walls that lead to attics or basements, or openings in outer walls of the house. If you find one bat inside your home, check and make sure there is not a bat colony living somewhere else in the house (usually the attic). Bats do not make or enlarge holes, but rather use pre-existing openings to enter buildings. They can enter a hole as small as 1/2 inch wide! Thoroughly inspect the exterior of the building for any openings, a hole that is used by bats is often discolored from body-oil residue. You can also find out where bats are roosting by watching for them at sunset when they emerge to feed.

If you have located a bat colony in your home and if you decide to exclude the animals, first find all the points where they are gaining entry. Seal all these entryways with hardware cloth or sheet metal, except the largest or most often used. Once all but one of the entryways are sealed, attach bird netting or flexible plastic strips with staples or duct tape over the last opening (leave the bottom open) to create a one-way exit. The bats will leave to feed and not be able to regain entry. Leave the one-way exit in place for several nights to be sure that all bats are gone, as not all bats leave the roost every night. After all bats have left, permanently seal the remaining hole. The months of May through August are not a good time to try to solve bat colony problems because it is likely that young bats will be present and they can’t leave the roost. The most ideal time is winter, after the bats have left to hibernate. Before this, you can try to coerce the bats into leaving by lighting the area continuously and using fans to cool the attic, which can make the temperature inhospitable to them. If you have a suitable area outside to install a bat house, you can encourage the bats to stay in your yard by giving them somewhere safe to live.

PUBLIC HEALTH CONCERNS

Although bats have been commonly associated with the transmission of rabies, the incidence of rabies in bat populations in the northeast has been estimated to be less than one-half of one percent. Bats with rabies generally are not aggressive and do not bite unless provoked. Nonetheless, if you have unknown contact with a bat it is necessary to have the bat tested for rabies and to notify your physician.

Areas that contain large accumulations of bat or bird droppings may harbor histoplasmosis fungi spores, which can cause infection in humans. To prevent exposure, avoid soil contaminated with bat droppings. If it is necessary to be in such areas, wear gloves, work boots, and a face mask or self-containing breathing apparatus, and contain exposed clothing in a bag until washing.

• MSPCA Bat Fact Sheet (pdf)
• Check out the Centers for Disease Control (CDC)’s site on bats and rabies
• BATCON: Learn about bat conservation and issues affecting bats
• Learn more about white-nose syndrome in bats