Introduction to Ontario’s Bats

By: Michael Allen Bryden

As the sun sets and dusk rolls in, you see a small black figure fly overhead in the sky, but that’s not a bird. You notice the erratic flight pattern of the figure and realize it could only be one thing. When the night comes in, the bats come out to play. Bats get a bad rep, but it is entirely undeserved. Very few bats in the world portray a vampire’s blood-sucking behavior, and you’ll be delighted to know that all of Ontario’s bat species do not drink blood. Ontario is home to 8 species of native bats, all of which are nocturnal aerial insectivores, meaning insect-eaters during nighttime. Not only do bats assist us in pest control, but they act as pollinators, pollinating important food crops and spreading seeds that one day become new trees. 

Roosting

During the day, bats are found hanging upside down within a roost. Most species of bats in Ontario roost in tight  spaces found in rock faces, loose bark, hollow trees, walls, attics, and bat boxes. These concealed places are not always immediately visible to the outside world. Guano, the name for bat poop, is often found beneath bat roosts projecting a strong smell of ammonia. Colonies found within these roosts can range anywhere from a few bats to thousands of individuals. Other bat species, such as Hoary Bat and Eastern Red Bat) form a different strategy, roosting in the foliage high up in trees. These species are often found roosting alone or in small groups. 

Feeding 

Being insectivores, bats have been known to eat moths, flies, beetles, dragonflies, and mosquitoes. In order to locate their prey in the dark, bats use a highly developed sense called echolocation. While echolocating, bats produce a series of high-frequency chirps that bounce around their surroundings and return back to their ears. Through interpreting these echoes, bats are able to visualize their environment. Although these chirps radiate at a frequency so high they often can not be heard by humans, they are unique to each species, and can often be identified by their frequency using acoustic recordings. How frequently a bat calls determines the accuracy of how they interrupt their surroundings. When they are hunting, bats emit a search phase pulse at regular intervals, but once they locate their prey, the chirps will increase in frequency until they are so close together that they sound like a buzz. This is known as a “feeding buzz” and allows the bat to hone in on its prey with as much accuracy as it possibly can. 

Reproduction

Very little is known about the reproduction practice of the Hoary Bat, Eastern Red Bat, and the Silver-haired Bat, but for the other species, the mating season begins in mid-August. During this time of year, bats congregate into large groups in abandoned mines or caves. These locations are known as swarming sites where bats gather to mate. Although little is known about swarming, it is known that very few bats roost within these sites during the day. Ontario’s bats are promiscuous, which means they mate with multiple partners in a single mating season.  Females are pregnant for 6-13 weeks depending on the species and start to give birth in early June. This is possible because of a female bat’s ability to store sperm in their reproductive tract during hibernation, and begin to ovulate and become pregnant the following spring. 

Compared to many other small mammals, bats have a very small litter size, with females usually giving birth to only a single pup each season. In the beginning, female bats sometimes carry their young while they fly and a small number of pups keep this manageable. This is different for one particular species, the Eastern Red Bat, which can have up to 5 pups a season. Around three to four weeks of age, the pups learn how to fly and begin their lives on their own. 

Overwintering

Due to the cold temperatures, and lack of insects, winter is an inhabitable time for bats in Ontario. To deal with this, bats in Ontario migrate. Cave bats migrate short distances to hibernate in other parts of the province, usually the Canadian Shield. These species of bats hibernate in caves or abandoned mines that remain above freezing temperatures. Provincially, 5 species, the Big Brown Bat, the Tricolored Bat, the Little Brown Myotis, the Northern Long-eared Myotis, and the Eastern Small-footed Myotis do so by entering an inactive state known as torpor. In this state, their metabolism slows and their body temperature drops to temperatures similar to that of their surroundings. In order for bats to maintain the energy needed to survive this torpor state all winter it is important that they are not disturbed. Disturbing a bat during hibernation will cause them to awake out of this state and burn important fat energy storage. On the other hand, Tree bats, which are the Hoary Bat, the Eastern Red Bat, and the Silver-hair Bat, migrate long distances to warmer climates for the colder season. These species are thought to migrate to the southern reaches of the United States and remain there until spring when the warmer weather returns. 

Ontario Bat Identification 

Ontario’s bats can be divided into two categories of cave bats, those who hibernate within their home range, and tree bats, those who migrate south for the winter. 

(The following 8 photos are credited to Brock Fenton)

Tree bats 

 

Silver-haired Bat (Lasionycteris noctivagans)

Medium-sized bat 9-11.5 cm in length  26-31 cm wingspan 6-14 grams in weight  Dark brown or black overall with white-tipped hairs on its back that give it a frosted look

Hoary Bat (Lasiurus cinereus)

Ontario’s largest bat (still weighs less than a chipmunk) 10-15 cm in length 34-42 cm wingspan 19-35 grams in weight White-tipped hairs contrasting with grey body fur Yellowish or toffee-colured face and throat Short round ears with black edges

Eastern Red Bat (Lasiurus borealis)

Medium-sized bat 8.5-12.5 cm in length 28-33 cm wingspan 7-18 grams in weight Yellowish orange to red fur White tipped hairs that give off a frosted appearance

 

Cave Bats

 

Big Brown Bat (Eptesicus fuscus)

Medium-sized bat 9-13 cm in length 32-39 cm wingspan 11-26 grams in weight Long dark brown fur evenly coloured across the back Lighter coloured underside Black hairless ear and wing membrane

Tricolored Bat (Perimyotis subflavus)

One of Ontario’s smallest bats 7-10 cm in length  19-26 cm wingspan 5-8 grams in weight Golden to greyish-brown appearance Back hairs are tricoloured with a dark brown base, yellowish-brown midsection, and dusky grey tips

Little Brown Myotis (Myotis lucifugus)

Small-sized bat 6-10 cm in length 21-27 cm wingspan 5-14 grams in weight Brown glossy fur on back and light fur chin to tail on the underside  Part of the difficult-to-identify Myotis complex

Northern Long-eared Myotis (Myotis septentrionalis)

Small-sized bat 7-10 cm in length 21-26 cm wingspan 6-9 grams Dull yellowish-brown fur with a pale grey underside Long rounded ears Part of the difficult-to-identify Myotis complex

Eastern Small-footed Myotis (Myotis leibii)

Smallest bat in Ontario 7-9 cm in length 21-25 cm wingspan 3-7 grams Coppery brown on the back and top of the head Black around the muzzle and eyes that creates a masked appearance  Part of the difficult-to-identify Myotis complex

 

What you can do to help

 

In 2006, a Eurasian fungus made its way to North American that causes white-nose syndrome (WNS) in bats. Over the years this disease has killed millions of hibernating bats and caused the most dramatic population decline of any group of mammals ever observed. Nationally, Northern Long-eared Myotis, Little Brown Myotis, and the Tricolored Bat species are labeled as endangered and provincially the Eastern Small-footed Myotis, as well as the previous three, are considered endangered. Recently land conversion for residential development in bat-friendly areas, and the introduction of insecticides, is removing food for bats. Night lighting is also affecting predator-prey patterns. 

 

If you would like to help protect local bat populations you can… 

• Avoid disturbing bats, especially while hibernating
• Provide critical roosting habitat by building a bat box (https://www.nwf.org/Garden-for-Wildlife/Cover/Build-a-Bat-House)
• Become involved in bat monitoring and protection (https://batwatch.ca/)
• Prevent the spread of WNS by disinfecting your clothes before entering potential bat hibernation sites (i.e. caves)
• Reduce night lighting by capping lights, using low wattage bulbs, installing motion sensors or timers on outdoor lights
• Don’t use insecticides, but instead let bats do theri amazing job at curtailing mosquito populations (some bats can consume up to 4000 in one night).