Bats at Ontario Parks

Today’s post comes from Natural Heritage Education Supervisor Alistair MacKenzie and Bat Stewardship Technician Heather Sanders.

Bats are the only mammal capable of true sustained flight, and with over 1,300 species and counting, they make up the second largest order of mammals.

Photo: Sherri & Brock Fenton

This is the order Chiroptera, meaning “hand wing” in Greek, and suitably their wings consist of elongated hand bones joined by a membrane of skin.

Most of us are familiar with the phrase “blind as a bat.” Bats are, in fact, not blind and have vision comparable to humans, but most species are nocturnal and use echolocation, a form of biological sonar, to supplement their nighttime vision.

Species of bats are found everywhere in the world except in the most remote Arctic and Antarctic regions, and therefore much variation is seen among different species.

Most bats eat fruit or insects, but some species have also been observed eating rodents, fish, frogs, birds, smaller bats, and the blood of livestock and birds.

Ontario’s bats

Little Brown Bat (Myotis lucifugus)

*Endangered in Canada*

Size: 4-11 g, average forearm size of 38 mm
Roosts: small, enclosed spaces including rock crevices, hollow trees, and human-made structures like houses, barns, and bat boxes
Diet: wide variety of insects, often found over water
Winter behaviour: hibernates in caves or abandoned mines
Fun fact: often found in houses, therefore frequently seen by humans

Big Brown Bat (Eptesicus fuscus)

Size: 10-21 g, average forearm size of 45 mm
Roosts: small cavities in hollow trees, rock crevices, and buildings
Diet: wide variety of insects, especially beetles
Winter behaviour: hibernates in caves, abandoned mines, or buildings
Fun fact: second largest bat species in Ontario; often found in houses and therefore frequently seen by humans

Eastern Red Bat (Lasiurus borealis)

Size: 8-18 g, average forearm size of 40 mm
Roosts: solitary in foliage
Diet: wide variety of insects, especially moths
Winter behaviour: migrates, but migration routes are unknown
Fun fact: high, fast fliers; often seen foraging around streetlights

Hoary Bat (Lasiurus cinereus)

Size: 18-39 g, average forearm size of 54 mm
Roosts: solitary in foliage
Diet: insects (especially moths), occasionally grass, small snakes, and small bats
Winter behaviour: migrates, likely to Mexico
Fun fact: largest bat species in Ontario; often seen foraging around streetlights

Tri-coloured Bat (Perimyotis subflavus)

*Endangered in Canada*

Size: 5-7 g, average forearm size of 35 mm
Roosts: small spaces or in foliage
Diet: wide variety of insects
Winter behaviour: hibernates in caves or abandoned mines
Fun fact: the only foliage roosting species in Ontario that roosts in groups

Silver-haired Bat (Lasionycteris noctivagans)

Size: 9-13 g, average forearm size of 41 mm
Roosts: cavities such as hollow trees
Diet: wide variety of insects, often over water
Winter behaviour: migrates, but migration routes are unknown
Fun fact: sometimes roosts on the outside of buildings during the fall migration

Eastern Small-footed Myotis (Myotis leibii)

*Endangered in Canada*

Size: 3-5 g, average forearm size of 32 mm
Roosts: few records exist in Ontario, but likely in small spaces such as area behind window shutters
Winter behaviour: hibernates in caves or abandoned mines
Fun fact: the least studied Ontario bat species; strongly resembles the Little Brown Myotis but is smaller with a dark facial mask

Northern Long-eared Myotis (Myotis septentrionalis)

*Endangered in Canada*

Size: 4-7 g, average forearm size of 36 mm
Roosts: in small crevices, under bark, or in human-made structures
Diet: wide variety of insects, including flightless insects and spiders
Winter behaviour: hibernates in caves or abandoned mines
Fun fact: the only bat in Ontario that has been observed gleaning (catching non-flying prey off of tree leaves, grasses, or the ground)

Why bats matter

Since bats are found almost everywhere in the world, they play an important role in many different types of ecosystems and provide many ecosystem services to humans.

Pest control

The majority of bat species are insectivorous, consuming up to their body weight in insects every night.

Many of these insects are damaging agricultural pests that wreak havoc on crops such as corn and rice. Research has shown that bats are worth billions of dollars a year in reduced crop damage and unneeded pesticide use, which means bats are helping our economy in addition to reducing the number of pesticides entering our ecosystems.

And more good news — bats also eat mosquitoes! One bat can consume up to 1,000 mosquitoes in one hour.


Many fruit- and nectar-feeding bats pollinate ecologically and economically important plants around the world.

In fact, over 500 species of flowers rely on bats as their major or exclusive pollinators, including bananas, peaches, cacti, and blue agave, the plant from which tequila is made!

Seed dispersal

batAs forests continue to disappear around the world, bats play a critical role in restoring natural areas by dispersing seeds of plants into clearings.

Unlike birds, who avoid flying over clearings for fear of exposure to predators, bats must cover large ranges at night to find food. This allows them to access areas unreached by other seed dispersers. In fact, seeds dropped by bats can account for up to 95% of first new growth!

Bats disperse seeds for many economically important plants as well, including cashews, figs, avocado, and papaya.

Threats to bats

Bats reproduce very slowly — females usually only give birth to one pup per year and as a result, it is extremely difficult for them to recover from substantial population declines.

Several major threats are causing significant losses to bat populations worldwide.

Habitat loss

Forests everywhere are disappearing at an alarming rate, usually as a result of timber harvesting, urbanization, or clearing for agriculture.

View of the forest looking up from the forest floor

Many bat species use forests to roost or forage for food. As these woodlands disappear, so too do the roosting sites and food supplies of these species. Other species roost in caves and are driven out by cavers, miners, or even tourists looking to snap a photo.

It is vital that bats are not disturbed when roosting; be sure to stay out of caves and plan maintenance work for buildings during times when bats are absent from buildings in the fall, winter, and spring whenever possible.

White-nose Syndrome

White-nose Syndrome (WNS), caused by a fungus called Pseudogymnoascus destructans, was first discovered in North America in late 2006. In infected hibernacula (caves where bats hibernate), the mortality rate can be as high as 80%-100%.

In total it’s estimated that WNS has killed approximately 10 million bats since 2006.

The fungus was found in Ontario caves in 2009, and continues to spread west. The four species of bats that are endangered in Ontario all hibernate in caves and have been affected by the disease. Learn more about White-nose Syndrome.

Pesticide use

Pesticides have been shown to have negative effects on many insectivorous animals, and bats are no exception. Pesticides are sprayed on plants or insects, then consumed by bats, storing them in their fat stores until winter.

During hibernation or migration, bats must utilize their saved fat stores. By this time, however, large amounts of pesticide can have accumulated in their stores, leading to pesticide poisoning.

In winter, this can mean excessive burning of fat stores and immunosuppression, making poisoned bats more susceptible to infection caused by the fungus responsible for White-nose Syndrome.

Even if a bat is able to survive winter poisoning symptoms, they are often plagued with reproductive problems such as stillbirths in the spring.

Learn more about threats to bats:

You can help bats!

To ensure Ontario’s bat species are around for future generations to enjoy, there are some simple things that you can do:

  • Build a bat box: Bat boxes are easily constructed (or purchased), and provide bats with critical roosting locations. Not only is this beneficial for your local bats, but you will be able to sit back and watch these amazing acrobats as they hunt for insects high above your backyard.
  • Give hibernating bats some peace and quiet: Entering caves or abandoned mines may disturb bats and reduce their ability to survive the winter.
  • Report any strange behaviour: If you see bats flying around during the daytime during the winter or see any dead bats, call the Canadian Cooperative Wildlife Health Centre, the Natural Heritage Information Centre or your local MNRF office.