Species At Risk

Little Brown Bat

(Myotis lucifugus)


Little Brown Bat


Little brown bats have glossy brown fur and usually weigh between four and 11 grams – about as much as a Canadian loonie or toonie. They are typically four or five centimetres long, with a wingspan of 22 to 27 centimetres. Little brown bats look similar to northern long-eared bats. They can be distinguished by the fleshy projection that covers the entrance to the ear. In little brown bats, the projection is long and thin, but rounded at the tip.

Little brown bats eat insects. They feed at night and are most active in the two or three hours after sunset. The female little brown bat usually gives birth to only one young, which is able to fly and obtain its own food when just three weeks old.

Action we are taking:


The little brown bat is widespread in southern Ontario and found as far north as Moose Factory and Favourable Lake. Outside Ontario, this bat is found across Canada (except in Nunavut) and most of the United States.


Bats are nocturnal. During the day they roost in trees and buildings. They often select attics, abandoned buildings and barns for summer colonies where they can raise their young. Bats can squeeze through very tiny spaces (as small as six millimetres across) and this is how they access many roosting areas.

Little brown bats hibernate from October or November to March or April, most often in caves or abandoned mines that are humid and remain above freezing.


Little brown bats are threatened by a disease known as white nose syndrome, caused by a fungus which is believed to have been inadvertently brought from Europe to North America. The fungus grows in humid cold environments, such as the caves and mines where little brown bats hibernate. The syndrome affects bats by disrupting their hibernation cycle, so that they use up body fat supplies before the spring when they can once again find food sources. It is also thought that the fungus affects the wing membrane, which helps to maintain water balance in bats. Because of this, thirst may wake bats up from hibernation, which may be why those infected with white nose syndrome can be seen flying outside caves and mines during the winter.

In Ontario, bat populations dropped by more than 90 per cent in eight hibernation sites with more than two years’ exposure to white nose syndrome. Bats at more than three quarters of Ontario’s hibernation sites are at high risk of disappearing due to white nose syndrome. Mass die-offs mean that there are no individuals left to reproduce.


The little brown bat (Little Brown Myotis) is listed as endangered under Ontario’s Endangered Species Act.

How You Can Help

  • Don’t enter non-commercial caves and abandoned mines where bats may be present. Avoid visiting caves and abandoned mines where white nose syndrome has been identified.
  • Bat proof your home. If a bat flies into your home, deal with it humanely. For tips, check out MNR’s Bats in your House fact sheet. [add link to new web page/fact sheet]. If you think you have a colony of bats living in your attic or barn, MNR has information on how to deal with it.
  • Consider building a bat box for your property. Learn more about how to build one and where to set it up. [SAR Branch providing URL]
  • Report any unusual bat behaviour or deaths to the Canadian Cooperative Wildlife Health Centre at 1-866-673-4781 or the Natural Resources Information Centre at 1-800-667-1940.
  • If you spot a little brown bat, report your sighting to the Natural Heritage Information Centre (http://nhic.mnr.gov.on.ca/MNR/nhic/species/species_report.cfm). Observations submitted by the public are very important in informing recovery planning, stewardship projects and other conservation initiatives for species at risk in Ontario. Whenever possible, include detailed location information and a photograph with your observation.
  • If you know of a bat colony, participate in MNR’s Summer Maternity Roost Monitoring Program [URL to follow – document not yet posted on MNR website].
  • Report any wildlife related infractions to 1-877-TIPS-MNR (847-7667).
  • Private landowners have an important role to play in species recovery. You may be eligible for stewardship programs that support protection and recovery of species at risk and their habitats. For more information contact the Ministry of Natural Resources at 1-800-667-1940.

Did you know?

Little brown bats are one of only two bat species in Ontario that are known to use human structures as summer maternity colony habitat.

Did you know?

Bats are the only mammals that can fly. Their wings are folds of skin stretched between elongated finger bones, the sides of the body, the hind limbs and the tail.

Did you know?

Although they usually live six or seven years, one little brown in Ontario was documented at 31 years old.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.