Bats

Bats are one of a select group of animals who have earned a well-deserved reversal of public opinion.

Not long ago, these diminutive creatures—they typically weigh no more than a few ounces—inspired such universal dread in humans that thousands were indiscriminately killed each year. Today, bats enjoy widespread favor due to an increasing awareness of their ecological benefits. Thanks to the individuals and organizations who have championed them, we now know that bats rarely cause problems for humans and frequently help control insect pests.

There are more than 40 species of bats found throughout Canada and the United States, all belonging to the order Chiroptera, the only group of mammals that are capable of flight. All common North American bats are nocturnal and feed on insects, which they usually catch in flight. They detect their prey by echolocation, which is the remarkable ability to emit high-frequency sounds—outside of human hearing—to discern objects by the sound reflected back to the bat. This sense is so acute that some species can detect objects no wider than a human hair. Different species of bats eat different types of insects, but as a group, all bats are considered beneficial because many of the insects eaten can be nuisance species.

Almost all bats migrate, often collecting in groups to hibernate in caves. Most species give birth to a single pup in May, and the newborn often clings to the mother while she hunts. As they grow too large to be carried, offspring are left behind. Attics are often used as nurseries because they maintain the desired temperatures for raising pups—although bats tend to have species-specific requirements. For example, big brown bats prefer that nursery colony temperatures not exceed 95°F, while little brown bats prefer the 110°F to
120°F range.

Problems and Solutions

Typically, conflicts between humans and bats only occur with a few species, including the little brown, big brown, evening, pallid, and free-tailed bats. These species often roost in houses (usually attics), sometimes for years, without being noticed by humans. Occasionally, an individual bat is found inside a house, flying around and landing on curtains or furniture.

The rule with any bat encounter is to remain calm and keep pets and children away. Keep as near to a wall as possible when moving around the room. Close interior doors and provide the bat with an exit by opening an outside door or window. Leather (not cotton) work gloves are adequate protection from a bat's teeth and will allow a person to safely and gently pick up a bat and release him outside, out of harm's way. Be prepared for the bat to vocalize loudly when he is picked up.

After the bat has been set free, it's important to find out how he entered the house. If open doors and windows can be ruled out, then it's likely the bat has been roosting within the outer walls of the house and has found a route to the living space. Common entry points include gaps around air conditioners, chimneys, and openings in interior walls that lead to attics or cellars. Inspect thoroughly, as bats can fit through openings as small as half an inch.

The key to excluding a bat colony from a building is to find any and all openings that the animals are using. A "bat watch" at dusk can help you find the entrances. Watch closely from before sunset until about 30 minutes after sunset. The best strategy is to let the bats leave on their own, then deny them reentry. However, bats should only be evicted when it is known that there are no young present. With that thought in mind, it is best not to solve bat colony problems from May through August. Waiting until they have left for winter hibernation also allows the exclusion to be done carefully and deliberately.

Public Health

Although bats are more commonly associated with the transmission of rabies to people than any other type of animal, the incidence of this disease in bat populations is estimated to be less than one-half of one percent. Rabid bats generally do not become aggressive and do not bite without provocation, but any bat may bite in self-defense if handled with bare hands. As we advise with any situation involving potential exposure to rabies, consultation with your physician and local health authorities is the recommended course of action.