Bats

Bats constitute nearly one-quarter of all the known mammalian species in the world. Like all mammals, bats are furbearing animals that feed their young milk produced in mammary glands.

Bats are nocturnal, meaning they are active primarily at night. They are also the only mammals to have achieved true flight, and are equipped with special adaptations that allow this:

bat

Living with Bats

Bats are generally shy and gentle creatures by nature, but they can often be misunderstood by people who encounter them. Better knowledge of bats is an essential tool in promoting their conservation.

Bat Houses

Did you know that bats can make great neighbours? Learn how you can build a bat-friendly habitat in your backyard!

Monitoring Alberta’s Bat Populations

Alberta is participating in a North American bat monitoring program. This program was initiated because of the declines in bat populations in eastern North America due to White-nose Syndrome (WNS). WNS is slowly moving west, so it is important that we learn as much about our bats as possible. Most of the monitoring will be with acoustic detectors, and we are hoping to locate maternity colonies in buildings (where females have their young every year) to monitor those also.

If you know of a maternity colony, please contact Lisa Wilkinson, Provincial Bat Specialist, at:

For further information on the bat monitoring program, see the US Forest Service website at:

Frequently Asked Questions About Bats

Flight and Navigation

How Do Bats Fly?

Bats possess several unique characteristics that allow them to achieve true flight:

  • The bones of the hand are elongated to support the thin double membrane of skin which forms the wings. The scientific name for the group — Order Chiroptera, means "hand-wing".
  • In most cases, there is also a membrane between the hind legs and the tail. This arrangement provides for amazing manoeuvrability, so that most bats are more adept at flying than many birds.
  • The flight membranes are also used to collect insects before they are eaten and to catch the newborn bats at birth. Some bats use their wings as raincoats while others use them as blankets.

although well adapted for flying, bats spend most of their lives hanging upside down asleep.

How Do Bats Find Their Way in the Dark?

The navigational system of bats consists of a highly developed sonar or echo-location system.

  • Ultrasonic sound waves produced in rapid pulses ranging from 20 to more than 500 pulses per second are bounced off objects around the bat.
  • Interpretation of the returning sound waves (the echo) allows the bat to determine the distance, speed, direction, texture, and size of an object.
  • This system of echo-location is extremely precise and individual bats have a remarkable ability to identify their own signals and avoid confusion even when surrounded by thousands of other echo-locating bats.

Vision is also important in navigating at short range. The aphorism "blind as a bat" has no factual basis.

Bats and the Food Chain

What Do Bats Eat?

All bat species in Alberta are insectivorous and feed almost exclusively on flying insects. In fact, they are the only major predator of night-flying insects. Baby bats of course eat only the milk produced by their mother.

As bats have a high metabolic rate, they must feed voraciously in order to meet the high energy demands of flight, thermoregulation, and reproduction.

  • Bats are very efficient feeders. Some species specialize in catching insects in mid-air, while others glean them from leaves and other flat surfaces.
  • A typical colony of little brown bats (Myotis lucifugus) can consume up to 50 kilograms (110 pounds) of insects during one summer. An individual little brown bat has been reported catching and consuming 900 insects in an hour!
  • In Alberta bats eat a wide range of insects, largely moths and beetles that are active at night.
  • Many of the insect species that bats eat are considered forest or agricultural pests or are a nuisance to people (such as black flies and mosquitoes)

Some prey species, particularly moths, have developed methods of detecting bat sonar and respond with patterns of evasive behaviour to try to avoid the predator. A few even produce their own sonar in an attempt to jam that of the bat or to warn of their distastefulness.

All bats also need to drink water.

  • They sleep in hot dry places all day and need to re-hydrate soon after they wake up each evening. Water also helps them digest the dry crunchy insects.
  • To get a drink, a bat flies low over a pond or lake or stream and simply opens its mouth and scoops up a mouthful of water.
  • Unfortunately, sometimes bats try this at uncovered rain barrels and they can’t swoop up in time to get out. These bats are often juveniles and some times they drown in the barrel.

What Eats Bats?

Very few animals eat bats as a main part of their diet. Their nocturnal habits (flying at night) keep most bats safe from being eaten by species that hunt during the day. In Alberta the major predators on bats are great horned owls (Bubo virginianus) and magpies (Pica pica).

  • Great horned owls will sometimes sit on a fencepost or traffic sign near a bat summer roost at dusk (just as the sun goes down). When the bats come out for their evening flight, the owls will try to pick off a few bats for supper.
  • Magpies sometimes pick off roosting bats that are sleeping during the day on the side of a building in the fall. These usually are juvenile bats.

In some tropical locations, humans eat bats as a delicacy. They make them into soup.

Bats in Alberta are not at risk of being eaten by people. However, people do pose a significant risk for destroying individual bats or the roosts and habitats in which many bats live.

Energy Conservation

How Do Bats Conserve Energy?

Energy-efficiency is a major guiding principle in many aspects of bat biology, including but not limited to a bat’s structure, behaviour, and daily and seasonal activities.

Structure

  • Bat bones are very light and their muscles are very efficient; this helps in flying.
  • Bats have a specialized form of fat that contains far more energy per gram than the fat of other mammals. No one has ever seen a ‘fat’ bat.
  • Bats sleep upside down for very long periods, days or weeks, without falling down. They use a special locking mechanism in their ankles that keeps their toes curled. It is similar to the mechanism in a horse’s knee that lets it sleep while standing up.

Behaviour

  • Have you ever wondered why bats always hang upside down? It is far more energy-efficient to go down than to go up, so bats use gravity to start their flight. They simply uncurl the toes on their back legs, open their wings as they drop towards the ground, and start to fly.

    This also is why bat houses have the entrance on the bottom of the house rather than on the side.

  • Bats avoid flying in cold, wet, or really hot weather. This means they do not have to try to keep warm or stay cool. (Although bats are pretty COOL anyway!)

Daily and Seasonal Activities

  • Bats sleep during the day and are active at night. By sleeping through the long hot summer days, bats conserve energy and also avoid competition with birds that eat insects during the day.
  • In Alberta, bats are near the northern limit of their distributional range. Since their insect food is abundant in summer but absent in winter, bats exhibit a seasonal pattern in their life history.
  • Bats in Alberta are all migratory, although the extent of migration differs among species. Individuals never spend summer and winter in the same roost.
  • Bats rely on the summer sun to heat the roost and, thus, promote the rapid growth of young bats. Indeed, young bats are some of the fastest growing mammals in the world.
  • Rather than maintain a steady body temperature like most other warm-blooded animals, bats can withstand a wide range of body temperatures. This allows them to take advantage of solar heat energy on warm days, while on cold days their body temperature drops as they enter a state of torpor to conserve energy.
  • Torpor is used in both summer and winter - whenever the environmental temperature dictates that it is better to be cool than to use extra energy to stay warm.
  • Bats are consummate aerial acrobats and are designed to conserve energy in all aspects of their flight dynamics.

Life Span and Mortality

How Long Can Bats Live?

although some bats may survive more than 30 years, as with many mammal species, most die in their first or second year.

  • In 2009, Fish and Wildlife bat surveyors in Cadomin Cave found and photographed a bat that was originally banded as an adult in the cave in 1975. This makes the bat at least 34 years old!

What Are Common Causes of Bat Deaths?

Diseases

Like other wildlife, bats can be vulnerable to disease. Traditionally, small numbers of bats have died from exposure to rabies.

In recent years, however, a more serious bat disease concern known as White-nose Syndrome has emerged. This disease has killed thousands of bats in Eastern North America, prompting preventative measures in places like Alberta which have not yet seen any cases.

Other Causes of Bat Mortality

Bats die for a lot of reasons other than disease. While natural predators take a toll on bat populations, additional mortality is associated with domestic cats, humans and wind turbines.

Humans

Unfortunately, many bats are killed by people, either intentionally by homeowners and vandals, or unintentionally by people destroying buildings and other roost sites.

Also, disturbing bats during winter can cause them to use up energy and die before the end of winter.

Domestic Cats

Contrary to what you might think, domestic cats kill a large number of bats, in addition to the millions of small birds that they kill each year. The usual scenario with bats is as follows:

  • Someone finds large numbers, often 10, 20 or more dead bats in their yard.
  • They call a Fish and Wildlife office concerned about possible disease killing the local bats.
  • Someone collects a sample of the bats and submits them to the Fish and Wildlife Diagnostic lab for examination and to try to determine the cause of death.

Invariably we find that all the bats suffered bite-related trauma. The bite evidence is consistent with having been bitten and killed by a domestic cat. The cats apparently carry the bats home to the yard to show off their trophy.

Wind Turbines

There is growing concern for the relatively high mortality of bats in association with wind energy facilities wherever they occur. Bat death appears to be related to abnormally low air pressure near the rotating blades of the turbines.

The research paper reporting these findings can be found at:

With the growing number of wind-energy generators in southern Alberta, the risk to migrating bats must be addressed. Through a co-operative consultative process the Fish and Wildlife Division, industry, and bat specialists developed:

Species, Habitat and Distribution

What Kinds of Bats Can Be Found in Alberta?

Nine species of bats have been identified in Alberta:

Only two species are encountered frequently by people: big brown bat and little brown bat.

The remaining species reside as solitary individuals where people seldom see them, or else they are easily confused with the two common species.

Where Can Bats Be Found in Alberta?

During the summer:

  • Bats can be found throughout Alberta in most habitat types, although they are scarce in the mountains and open prairies.
  • They are widely distributed in the northern forests, western foothills, and central parklands.
  • They occur often along large prairie rivers.
  • Bats live in rural and urban settings, even in Alberta’s large cities. In fact, a good place to watch bats is around street lights late in a summer evening as they hunt insects attracted to the lights.

During the winter:

  • Like many wild species (and some people), most bats leave Alberta in the winter.
  • Those bats that do not leave often stay in caves and mines in the foothills and mountains.
  • Some bats stay in rock cliffs along large prairie rivers.
  • Bats are rarely seen in Alberta in the winter because they spend all their time asleep.

There are far fewer bats in Alberta during the winter than there are during the summer. Frosts that kill the flying insects are their cue to leave in the fall. This usually occurs in mid to late September.

Warming temperatures and the reappearance of flying insects are the cue for bats to come back in the spring. This usually happens in early May.

Species, Habitat and Distribution

What Do Bats Do in the Winter?

Some bats stay in Alberta. Others migrate to southern locations. Bats are true hibernators and regardless of where they are, our bats go to sleep in the winter. They spend from five to seven months in a state of torpor (deep sleep).

  • In Alberta, hibernating bats have been found in natural caves in the mountains and foothills, in nooks and crannies in the rock cliffs along some rivers, and a few individuals of one species occasionally overwinter in buildings that are ‘not too hot and not too cold, not too wet and not too dry’.
  • Hibernating bats do not feed or drink, and their body temperature and metabolic rates decrease markedly. This energy-efficient state allows them to sleep away the long northern winters.
  • They may wake up now and again for short periods but very quickly go back to sleep.
  • Since bats cannot replace their stored energy (there are no flying insects available during the winter), they must conserve what they have and make it last all winter.
  • Disturbing bats during winter can cause the death of many bats that run out of energy and starve. When they are disturbed, bats wake up and try to avoid whatever disturbed them. This uses up large amounts of energy that cannot be replaced.
  • In Alberta it is illegal to disturb bat (or snake) hibernation sites between September 1 and April 30 each year.

There is little information about the winter habits of bats in Alberta and it is not known specifically where the majority of our bats spend the winter.

Where Do Bats Roost in the Summer?

There are basically two types of bats in Alberta in the summer: those that roost in colonies in buildings and those that live alone in trees or rock crevices.

Buildings

  • Numerically, there are far more bats that live in buildings. They gather in colonies that range from a few bats to a few hundred bats in one building.
  • Colonies can be found in houses, barns, garages, hospitals, hi-raise apartments, shopping malls, and just about any type of building.
  • Within the building, they prefer small dark spaces that are poorly ventilated and heat up during the day. The optimum temperature in these roosts is 39° to 42°C (102.2° to 107.6°F).
  • Bats can only enter a building by going through a hole that already exists, such as a crack or a vent. They cannot chew holes into or inside a building.
  • Roosting sites usually are within a few hundred metres of a source of water. The water provides moisture for drinking, which the bats obtain by swooping low over the surface. It also supplies an aquatic habitat to support high concentrations of insects.

Within buildings, bats commonly live:

  • In eaves and attics
  • In walls and roofs
  • Behind soffits and facing boards
  • Around chimneys

They may take up temporary roosts:

  • Behind shutters and sliding doors
  • Under shingles and sidings or even in the open on walls
  • Under or between thick cedar shakes
  • Inside closed patio umbrellas!

Trees and Rocks

We do not know nearly as much about bats that live among trees and rocks. We do know:

  • Individual bats often go back to the very same tree summer after summer.
  • Tree bats roost among the leaves or needles, under the bark, or in cracks and holes in tree trunks, often in old woodpecker nests or frost fractures.
  • Bats in rock cliffs may use the same cave or crevice year after year.

Publications

Web Resources

  • Alberta Bat Action Team

    The Alberta Bat Action Team (ABAT) is a working group dedicated to improving bat species conservation and management in Alberta.

  • Human-Wildlife Conflict: Bats

    Information from Alberta’s Fish and Wildlife Officers about how to reduce conflicts between bats and humans.

  • Research Licences and Permits

    Information for wildlife researchers on research permits and protocols. Bat related information includes Class Protocol #004: Bat Capture, Handling and Release.

  • Sensitive Species Inventory Guidelines

    Information for wildlife managers to improve data collection on sensitive species in Alberta, including bats. Bat related guidelines include:

    • Bat inventory protocols
    • Bat survey data sheets
    • Bats and wind survey protocol

Wildlife Diseases

Learn about the diseases and parasites associated with Alberta’s bat species.

One disease of particular concern is White-nose Syndrome, which has impacted bat populations in Eastern North America. Efforts are underway to educate the public and prevent the spread of this disease to bats in Alberta.

 

Page Information

Updated: Oct 19, 2015