As the sun sinks below the horizon, bats release their footholds and drop headfirst from their perches. In a dark mass of beating wings, they emerge from caves and crevices to hunt for prey. They navigate through the night skies guided by sonar. Considering their unusual nature, is it any wonder that bats have found their way into the mythology of so many cultures?

The ancient Egyptians believed that a bat hung over the doorway could prevent the entry of demons that caused poor eyesight, fever and even baldness, according to Dr. Thomas H. Kunz of Boston University. Prior to the arrival of early European explorers, bat gods were important to many civilizations in Central America. Bats have also been used in voodoo worship in Africa. Perhaps the most famous legend is that of vampires that can transform themselves into bats. Interestingly, this myth shares a connection with the first European explorers in the New World. Stories of "human" vampires in Transylvania predate the discovery of the New World; bats only became part of the legend after Cortez visited Central American. There, the Spanish conquistadors first saw (vampire) bats that fed off the blood of livestock and wildlife.

Fortunately, in North America, bats consume not blood but, rather, vast quantities of mosquitoes and other insects. The common brown bat, for example, can consume thousands of mosquitoes each night! Bats play a role in maintaining a balanced ecosystem, which is especially important considering the recent introduction of West Nile virus to the American continent. This potentially deadly virus is transmitted to humans by mosquito bites. A healthy population of bats in your neighbourhood may be the most effective and certainly the cheapest form of mosquito control available. When bats move into our homes and garages however, we tend to view them as pests because they can create problems.

Odor

If bats have taken up residence in your home, you may notice whitish droppings around an opening where they enter and exit the building. They can eliminate wastes during mid-flight and also tend to soil their own roost. In fact, bats often return to the same roosts repeatedly and, over the years, some very potent ammonia odors can accumulate.

Sounds

Bats emit audible clicking or squeaking sounds. The sounds may bother dogs because they can hear the high frequency sounds beyond the range of normal human hearing. If bats have found their way into your home, you may also hear scrapping sounds in the walls as the bats fly in and out for feeding.

Disease

Bats try to avoid human contact so it is very unlikely that you will ever be bitten by one unless you try to handle a trapped or injured bat. If a bat has flown into your home or you find an injured bat on your property, do not attempt to handle it with your bare hands. As with most animals, stressful situations can lead to aggressive behavior including biting.

Rabies can be transmitted to humans by bites from bats although the incidence of infection in these animals is statically quite low. Estimates range from 0.5 percent to 2 percent. If you encounter an injured bat that is unable to fly, be extremely cautious, as rabies may be the cause of its physical weakness. If you are bitten, rinse the wound with soap and water then disinfect with a generous amount of rubbing alcohol. Call a doctor and your local public health department. An effort should also be made to capture the bat so that it can be tested for rabies.

Another health problem associated with bats is a lung disease called histoplasmosis. The disease is caused by a fungus that grows in the moist bat droppings (guano). If the air-borne spores of the fungus are inhaled, they can cause pneumonia-like symptoms. The likelihood of illness increases when the fungal spores are present in high concentrations as is the case when the bats roost in an enclosed area with little air circulation.

Evicting Bats from your Property

Considering the odor and health problems mentioned above, bats and people are not really meant to live in close proximity. It is best to appreciate them from a distance. If a colony of bats has decided to take up residence on your property, the following tips can help you evict them effectively and without harming these important wild creatures.

Using chemicals or poisons to repel or kill bats can be illegal (if the species is endangered or threatened) and also harmful to pets and children. Repellents such as mothballs and ammonia are generally ineffective for evicting bats because they often return when the chemicals have dissipated. Poisons may make the bats sick and fall to the ground where there is a greater chance that they will come in contact with curious pets and children. Shining bright incandescent or florescent light on the roost for several days can be an effective deterrent in some cases. Be sure that the bats have a way to exit the building. Keep a close watch for their departure, then seal up the entry/exit hole.

Sealing up the holes in a building is the most effective way to prevent bats from taking up residence in your house or other buildings. If bats are already roosting in the building, you want to ensure that you do not trap any bats inside. Timing is crucial. North American bats either hibernate for the winter or migrate south. In the spring and summer, female bats give birth and spend more time in the roost. Do not seal up the holes from May to July as you may trap and kill bats that are too young to fly. The best time to check for bats is in February. Take a careful look around your attic or and other dark, protected areas of your home where bats may colonize. If you do not find any bats, seal the entryways with flashing, plywood or other siding.

If you find bats during your inspection, the best approach is to install one-way exits. This can be accomplished by attaching a PVC tube that has a collapsible plastic extension on the end. Bats can exit through this device but they cannot reenter. Contact your local branch of Environment Canada or municipal animal control unit for advice and assistance with installing these devices. These organizations can also provide you with information about setting up bat boxes in your backyard to accommodate the evicted bats.

Just remember that although bats are pests to humans in some respects, they are also fascinating and complex creatures that can help us enjoy pest free summer nights!