Little Brown Bat (Myotis lucifugus)
Ontario, Canada

Nineteen species of bats have been recorded in Canada, and 17 of them are regular residents. In many ways bats are typical mammals: they are warm-blooded and they give birth to live young and suckle them. They differ from all other mammals, however, in their ability to fly. Their wings are folds of skin stretched between elongated fingerbones, the sides of the body, the hind limbs, and, in Canadian species, the tail. A resting bat usually hangs head downward and takes flight by releasing its toehold.

The little brown bat is the most common, and best-known bat in Ontario. It lives in all parts of Canada in large numbers.

Bat Viewing

Bats have a bad reputation. That is because ordinary people know so little about them. They fly mostly at night so people seldom see them. They are nocturnal. They often fly close to animals, including humans, since insects often collect near animals. They never fly into people's hair.

If you see what looks like a swift little black bird flying by you at dusk, it is probably a bat. Most small birds, like sparrows or finches, hide from owls by that time of the day. You may also see bats just after dark, near window lights or by moonlight. Little brown bats often swoop by a few times just above your head while catching insects. Sit down quietly and enjoy this interesting little mammal.

Many of the abondoned mines in the area are ideal places for bats to congregate and can be found hanging from the ceiling, in cracks and crevices of these mines.


The easiest way to describe a bat is to say it looks like a mouse with wings. With smaller eyes, large ears and larger mouths full of teeth, they look fiercer than mice. Bats are the only mammals that truly fly. Although the wings are often hairless and even transparent in places, the body of the bat is covered with soft fur.

Flying bats appear larger than resting bats because of their large wing area.

Overall colouration, brown; buffy gray underneath. Wings, bluish-gray.

wingspan of about 22cm

7.9 - 9.4 cm (3.1 - 3.7 in)

It is 8 to 9 cm long and weighs from 3.1 to 14.4 g depending on age and season of the year. The brown hair on its back has glossy, coppery tips, and its belly is buff-grey.

Bat Wings

Bat wings are made of greatly lengthened hand and arm bones covered by a wide membrane or skin. The skin is attached to the lower leg near the ankle so that the wing is almost as wide as the bat's body is long, from nose to toes. Using powerful muscles, the bat doesn't just flap its wings up and down like a bird. It swims through the air reaching forward in an action much like a breast stroke with up to 20 beats a second. It can also glide on air currents much like a gull or hawk. A claw, really an extended thumb, sticks out from the end of the forearm. The bat uses it to cling to whatever surface it lands on. A small bone, called the 'calcar, sticks out from both ankles in flight. It holds a tight skin called the 'interfemoral membrane' between the legs, covering most of the thin tail. The bat uses this membrane in gliding and catching insects. When it stops flying and lands, the bat folds its wings along its forearms and can walk, climb or swing with its clawed feet. Some can even swing from branch to branch. At rest, the bat hangs upside down from one or both hindfeet. While hanging from one hind foot, it can use the other to groom its fur and clean its teeth.


By day, bats roost in caves, mine tunnels, in the leaves of trees, in attics and under the roofs of barns or abandoned buildings and other building crevices. At dawn then fly out to catch insects.

The little brown bats live mostly near forests or clumps of trees where it hunts for insects at night. During the summer, the bats often roost in the attics of cottages or houses. In groups of from 50 to several hundred, females may give birth in barns. The males, unlike the females, usually roost alone, in any small hole they can find. Scientists know little about where male little brown bats use to roost except that they have different daytime and nighttime roosts. Little brown bats can stand temperatures as high as 61 degrees Celcius. They can live in hot attics that other bats cannot stand.

In late fall, the little brown bats often travel hundreds of miles from their warm-weather hunting areas to find winter roosts in which to hibernate. They must find caves or abandoned mines that stay a few degrees above freezing and have a humidity close to 80 percent (very damp). Most return to the same winter roost year after year. Male bats usually arrive first and make supersonic sounds to attract females. The female lands near the male and mates. Males and females mate with many different partners. This happens over several days. They mate until cool temperatures gradually put the bats into hibernation. The female holds the sperm in her body until spring.

Bats are primarily nocturnal creatures, sleeping during the day and hunting and feeding at night.

Ontario bats are only be active in the province during warmer months when insects are abundant. In winter, they either hibernate or fly thousands of miles south to warmer places. Most hibernate. Only a few species migrate south.

Hibernating bats have a problem. If the place where they hibernate falls below freezing, they die. If the cave or building is too warm, they will use up their store of fat too quickly and starve to death. Bats can wake up from hibernation very quickly. They can escape danger that way. Other Ontario animals that hibernate take much longer to wake up.


Brown Bat's feed on insects, all of the bats in Ontario only eat insects. usually caught in flight. They catch the insects in mid-air with their mouth, wing, or interfemoral membrane. They can flip the food from the wing or membrane into their mouths in mid-flight. If the insect is too large to swallow, they will land on their feet to eat it. Bats will take moths, mosquitoes, beetles, mayflies, caddis flies, and midges. Insectivorous species of bats typically consume 30 – 50% of their body weight in insects each night.

They fly out about dusk to a stream, pond or lake to get a drink. They drink by scooping the water up in their lower jaws, sitting beside the water. They can also scoop up water while flying over the water's surface.

Little brown bats are very beneficial to man since in a single minute they can eat seven or eight insects, including water insects that they skim off the water of ponds. If they happen to crash into the water, they can swim. This bat can fill its stomach in 15 minutes and empty its digestive system several times in a night between feedings.

Breeding Biology

Bats hibernating in one roost seem to give birth all on the same day. Young bats are unusual among mammals because they are born feet first. The mother feeds her one or two youngsters on rich milk and often carries them on her back while she flies looking for food.

Because it forages at night, the little brown bat is far less subject to predation than other species and does not need to reproduce in large numbers.

Little is known about the lives of adult males during the summer. They do not live in the nursery colonies with females and babies, and it is presumed they roost alone or in small groups in cracks and crevices.

Early in August adult males make nightly visits to the caves and mines that will serve as hibernation sites. They arrive at these locations after feeding and spend several hours underground.

As August progresses, more and more adult females and young join the males at these hibernacula, and by the middle of August the first matings take place. Most of the mating occurs before the population of hibernating bats builds up in September. The females store sperm in the uterus over the winter; ovulation and fertilization occur when the females leave hibernation in the spring.

In the summer female Little Brown Bats aggregate in colonies that often are located in the attics of buildings. Several hundred Little Brown Bats may inhabit one colony, moving into it sometime in April or May. Males do not live in the nursery colonies with females and babies.

Each female gives birth to only one young bat although twins are not uncommon, once each year. In spring, usually around the middle of June, after 50 or 60 days of gestation (development of an embro in a mother's body), an almost hairless youngster is born. Bats hibernating in one roost seem to give birth all on the same day. Young bats are unusual among mammals because they are born feet first.

The mother feeds her one or two youngsters on rich milk. For a few days, the young bat clings sideways across it mother's chest so that she will not be unbalanced and goes with her as she hunts insects through the night.

After a few days, females leave their babies in the roost each night when they go out to forage and unerringly select their own baby from the many others awaiting their mothers' return to give it more milk.

The female later leaves scent markings near the hidden roost. Scientists believe the scent markings help the young bat find its way back. The young bat can then make its first moves to explore. If the young bat falls from its perch, it will call out and the mother will carry it back to its roost.

Baby Little Brown Bats grow rapidly, increasing their wing area by 10 times in three weeks and starting to fly by the age of 18 days. By this time they have shed their milk teeth and begun to eat insects as well as their mothers' milk.

The months of July and August are spent in heavy feeding as the females and young build up their fat reserves for hibernation.


Besides people, the enemies of bats are owls, hawks, skunks, snakes, mink, raccoons, cats, and dogs.


Since they can live until they are 24 to 30 years old in the wild, they must be able to avoid their enemies fairly well. More little brown bats die from accidents and disease than by being eaten by a preditor. Usually bats live four to eight years.


Ontario bats have small eyes and poor vision but they do not bump into things. They use 'echolocation' in the air that works somewhat like sonar does underwater. The bat makes a series of high pitched sounds through its nose or slightly opened mouth. There could be 30 to 60 rapid squeaks a second. These sounds are very high pitched, 30 000 to 100 000 cycles per second. They are far beyond human hearing.

The squeaks bounce off even the tiniest insect back to the bat's enlarged ears, telling it exactly where the insect can be found. Muscles in the ears open and close rapidly, blocking out the sounds given off but picking up those echoed back. The bat can tell the size, exact location, and speed of any object. The bat can also tell the direction of movement and even thickness of the object. It can use this remarkable method of hearing to find any insect, plant, building, or possible enemy in total darkness. As well as these 'supersonic' sounds, the bats do make sounds that people can hear. Bats make these lower-pitched sounds when they are upset or excited. They also use them when mating.

Bats and People

The bat droppings are called guano and are rich in nitrates. Farmers in many countries collect it for fertilizer, but it is rarely collected in Canada. The guano, which can be smelly, is the main reason people fumigate their cottages, barns, and attics to be rid of the bats.

Bats benefit people by consuming great numbers of insects. Scientists estimate that a little brown bat, the commonest bat in Ontario, eats a gram of insects an hour while hunting. The little brown bat weighs only 3.5 to 6 g. Of course, it can eat more during spring and fall when there are more hours of darkness. It needs more food for raising young in the spring, and for putting on fat for winter hibernation. Scientists have studied blood circulation, wound healing, and the effects of gases using the thin wing of a living bat. Sometimes bats roost in poorly sealed attics and must be killed or forced out by fumigating.

After rodents, these are the second largest group of mammals in Canada or the world. The fact that few people remember seeing them should make you realize how little harm they do to people. No one knows how many bats there actually are in Ontario, but some scientists think there are as many bats as there are birds. Think what would happen to the number of insects if there were no bats.

Like all other mammals, bats are susceptible to rabies, a viral disease that causes progressive paralysis and death. The virus is usually transmitted by the bites of infected animals, as it is found in the saliva. The incidence of rabies in bats in Canada seems to be low, although there have been no studies of its general incidence in the bat population. Some species are more often found rabid than others, and there is geographic variation in the incidence of rabid bats. As a general precaution, people should avoid handling bats. Healthy bats will bite in self-defence; so will rabid ones. In some cases, rabid animals will attack without provocation. If you are bitten by a bat or any other mammal you should immediately contact your physician and Agriculture Canada personnel, who can arrange to have the animal that delivered the bite tested for rabies.