Bring In The Bats

By: Kevin Plessner

We have a bat problem in Maryland, but the problem is probably not what you think. Unfortunately, the bat population has been decimated in our state and the loss of our bat population has brought dire consequences for our community and our ecology. Due to the various myths and fears that people commonly have about bats, I think that a good place to begin to tell our bat story would be with a brief description of what a bat is, and more importantly, what it isn’t.

What is a Bat?

Contrary to popular belief, bats are not rodents. In fact, bats are more closely related to humans than they are to mice! They are the only mammals that have developed true flight, therefore they are put in their own scientific order: Chiroptera (hand-wing). There are ten species of bats in Maryland and each one of them eats exclusively insects (bat species in other parts of the world also commonly eat fruit and pollen in addition to insects). There is no such thing as a “vampire bat” in Maryland (or even in North America).

Why Do We Want Bats?

In Maryland and other parts of the world, insect-eating bats are the primary predators of night-flying insects including moths, beetles, gnats, mosquitoes, and flies.  In fact, one little brown bat in Maryland can eat several thousand insects each night. Insect-eating bats reduce pests and therefore reduce our use of pesticides. That means bats directly make our air and water cleaner and help us to protect wildlife. Pesticides lead to increased food costs and can lead to health issues in humans.  With fewer bats, insect populations will continue to grow. Rising insect populations increase our dependence on pesticides and rising food production costs. Escalating insect populations also increase the chance for mosquito and other insect-borne diseases (such as the Zika virus).

In other parts of the world, nectar-feeding bats help pollinate plants, including those that provide food for humans. Fruit-eating bats help to spread seeds. Humans have also found bat guano (feces) to be very useful to be used as fertilizer and making gasohol. Bacteria in their guano are helpful in improving soaps and antibiotics as well.

Bats are crucial to gardeners and farmers, playing an important role by eating thousands of pest insects that feed on the crops we grow such as the tomato horned worm, corn earworm and various types of beetles. Unfortunately, due to many years of fear and misunderstanding, bat populations around the world are decreasing and some are nearly extinct.

Vampire Bat Myths

So-called “vampire bats” have been portrayed as scary and vicious animals seeking to suck the blood of unsuspecting people. This is certainly not the case – bats do not suck human blood. There are only 3 species of bats that have a taste for blood (primarily of cows, chickens and other animals) – and they all live in Central and South America.

Interestingly, it is in the mouths of these tiny mammals that scientists have found a powerful drug for the treatment of blood clotting diseases. The saliva of a vampire bat contains a special clot busting protein that has been synthesized and the resulting drug is called desmoteplase or DSPA after the scientific name for the common vampire bat Desmodus rotundus. This drug is being used in trials to treat thromboemboli (loose blood clots in the body) which may block important blood vessels in the lungs (pulmonary embolism) and brain (stroke) and can result in death. Initial trials have shown that the drug works much more quickly and effectively at breaking up pulmonary blood clots than traditional treatments. Thanks to increasing research into bat biology and medicine you too may one day be saved by the bite of a vampire bat.

Is there Anything I Can Do to Help? Build a Bat House!!

Bat houses in Maryland and most other places have been proven to provide a habitat for bats. If you build them a home, they will help you by eating your unwanted mosquitos and other insect pests.

As the human population continues to grow, human-wildlife altercations will also increase.  Bats prefer to live in dead trees during the summer. Without natural habitat, however, bats will take up residence in human-made buildings since their natural habitat is no longer available. Mounting a bat house on a pole, tree or the side of a structure is the best way for us to provide a suitable alternative to our homes. Unless alternative housing is available, bats will continue to adapt to living in our homes.  This greatly increases the chance of human-bat contact. It is to the benefit of the health of the community to place up bat houses to provide alternatives.  

Here are some of the benefits to putting up a bat house:

·        Bat houses give bats a home and in turn they will eat thousands of insects for you each night.

·        Bat houses give bats an alternative to our homes, thus reducing the chance of human to bat contact.

·        Bat populations have decreased significantly in recent years and bat houses can help provide them with a safe and secure habitat for bats to roost during the day and to raise their young.

·        If you choose, you can use the guano (bat poop) for your garden. Place a potted plant under the bat to collect the guano, it's high in nitrogen and plants love it.

·        Fewer insects means fewer mosquitos, termites and other insects, which means less pesticides, a healthier ecosystem and therefore a healthier Linthicum.

Bat houses should be mounted at least 12 to 15 feet off the ground, and facing an open, sunny location. They work best if placed on a pole, the side of building, or a tall mature tree with a lot of trunk space. I have provided some links to bat house building plans below, but they are also available online and in local stores (Amazon, Home Depot and Walmart to name a few) and are relatively inexpensive to build.

It’s important to note that in Maryland, bats generally hibernate during the cold winter months from September or October until March, April or May. The temperature will determine how soon they go into hibernation and how soon they emerge from hibernation.  During mid-fall they leave their summer roosting site and fly from a few miles to a few hundred miles to their hibernation site (the hibernation site must be cool but remain above freezing).

Wait, I Heard that Bats Can Give Me Rabies…

Rabies is a fatal disease transmitted from one animal to another by biting. Rabies kills about 30,000 people in the world each year. However, 99% of these cases are transmitted by dogs—rabies in bats is not common. Over the last 50 years, only about 40 people in the United States have died from rabies contracted from a wild bat, even though hundreds of millions of bats live in this country and millions of these animals roost in buildings frequented by humans. 

The last reported death in Maryland attributed to bat rabies occurred in 1976. A 55-year old woman was bitten on the hand by a bat; the species was later identified as Silver-haired Bat/Eastern Pipistrelle Bat (this species has not been shown to reside in bat houses in Maryland). Rabies data from 1991-2000 provided by the Maryland State Department of Health and Mental Hygiene show that skunks, raccoons and foxes have the highest prevalence of rabies in Maryland. In addition, bats are not “carriers” of rabies—when a bat gets the disease, it will die.  Bats also tend to become paralyzed with the disease, often avoiding the aggressive form of rabies.

Statistically, more people are killed by lightning strikes and dog attacks than rabid bats. That being said, there are several ways to further reduce the chance of coming in contact with an infected wild bat.  It is always recommended that all dogs and cats (indoor and outdoor) be vaccinated against rabies, wild bats be humanely evicted from living quarters and alternative housing be provided (e.g. a bat house). 

Will A Bat Attack Me?

Picking up a bat with bare hands is the most common way in which people are bitten.  Most animals will bite in self-defense, and bats are not an exception.  Avoid contact with all wild animals by keeping a safe distance.  If bitten by any wild mammal or stray dog or cat, contact your physician and Animal Control to have the animal sent for testing. If you have been bitten by a bat, wash the wound with soap and water and call your county health agency immediately. Prompt medical treatment and a series of five shots in the arm can prevent a person from contracting rabies. For more information on rabies and wildlife and when to consider post-exposure treatment, visit the Centers for Disease Control website.

Keep these things in mind if you come across a bat:

1.      Don't panic!

2.      If the bat is outside, leave it alone.

3.      Bats do not attack people. They are afraid of humans, viewing us as predators, and will avoid us when possible.

4.      Like any wild animal, a bat can bite if threatened. If you need to relocate the bat, do not touch a bat with your bare hands. Call Animal Control.

5.      Bats are protected and important animals that play a key role in balancing ecosystems.  We should try to never cause harm to bats.

The Following Websites Contain Simple Bat Box Plans:


Acknowledgements: Statistics and facts contained in this article were provided by the Maryland Department of Natural Resources, the Organization for Bat Conservation and the Maryland State Department of Health and Mental Hygiene.