Written by Maria MacRae
Illustration by Michel Poirier

The little brown bat is the most common and widespread of Canada's nineteen species of bats. They are found across Canada to the northern edge of the boreal forest.

One of the smaller Canadian bats, little browns weigh only seven to fourteen grams and have a wingspan of 22-27 centimetres. This species of bat is the one most closely associated with humans, as it is the most likely to take up residence in buildings.

Little brown bats play an important role as predators of night flying insects. They are very efficient hunters capable of catching over 1000 insects in just one hour. Little brown bats concentrate on insects that have an aquatic larval stage, such as mosquitoes, midges, and mayflies. Consequently, they prefer roosts in the vicinity of water. Although they prefer to forage over water, they will also hunt in open areas where they catch moths, beetles, and other flying insects.

Contrary to the myth that bats are blind, little brown bats have excellent vision. Although echolocation is important, they also use visual cues, especially during long distance migration. Echolocation, the use of high frequency sounds to navigate, is used for finding and catching prey. Their skill in echolocation is such that they are able to avoid obstacles as fine as a human hair. (It is a myth that bats get caught in human hair.)

There are a number of predators that feed on little brown bats, such as raccoons, hawks, owls, and snakes. They are dependant, therefore, on finding roosts that provide protection from these predators while still being close to food and water sources. Little brown bats form a strong attachment to their maternity site and will return year after year to the same location.

In the winter, little brown bats move to caves and mines for hibernation. They find an area of the cave with high humidity and a constant temperature slightly above freezing. Forced to survive the winter on their stores of fat, bats slow their heartbeat from approximately 200 beats per minute to as low as 20 beats per minute to conserve energy. It is important that they are not disturbed while hibernating as this causes them to waste precious fat reserves. Extra arousals can leave them with insufficient energy to survive the winter.

Pesticides harm bats through direct contact and by limiting their food supply. Some farmers have been able to reduce their dependence on pesticides by welcoming bat colonies to their land. They provide artificial roosting sites for the bats, which in turn devour insect pests.

If you would like to help bats in your area you can provide roosting sites by putting up a bat house. Little brown bats are one of the bats most likely to use bat houses.