Why attract bats?
Although often maligned, bats are actually an important ally for gardeners. They are the primary predators of night-flying insects, including moths, beetles, and mosquitoes. By controlling these insect populations, bats help keep garden pests, such as cutworms or corn earworms, under control.
All bats in Canada are insectivorous, meaning they eat insects. They are very efficient hunters – most consume up to 50% of their body weight in insects each night. Little Brown Bats, the most common bat in Canada, can catch hundreds of mosquitoes in just one hour. Many insects have developed the ability to hear bats even at great distances, so that the mere presence of bats in an area will vanquish insect pests.
Bats are proficient hunters because of their prowess at using echolocation. They send out pulses of sound that echo off objects allowing them to locate and identify their prey. They are so skilled in both echolocation and maneuverability that they can rapidly detect and avoid even the most delicate of obstacles. (The myth that bats get caught in people’s hair is just that – a myth.)
How to attracts bats
Bats are attracted to an area if it meets their need for food, water, and shelter. The presence of a fairly large source of fresh water, especially a stream, river, or lake, is one of the key indicators of good bat habitat. These areas provide not only fresh water, but also an excellent supply of insects.
A number of bat species in the Ottawa area are known to use bat houses, in particular the Little Brown Bat and the Big Brown Bat.
The success of a bat house in attracting inhabitants depends on a number of factors:
- The roosting cavity should be about 2 cm (3/4″) deep.
- Houses should be painted a dark colour to absorb heat for greater warmth. Use a water-based paint or stain.
- Proper caulking prevents drafts and keeps the inside temperature stable.
- Houses should be located to receive maximum sun exposure (houses placed on trees often do not receive sufficient sunshine).
- Protect bats by ensuring there are no nearby limbs that allow easy access for predators. Mounting the roosting box on the side of a house or on a tall pole provides the best protection.
- Bat houses should be 5–10 metres from the ground with a clear path to the entrance, i.e., no tree branches or structures obstructing flight.
- Do not place bat houses near bright lights (some bats even fear to venture out on nights with a full moon).
Bat house. Bats enter from the bottom. There are five vertical dividers, etched laterally for easy climbing and holding. Photo D. Gordon E. Robertson.
Even the most spectacular, well-placed house will not attract bats if it is in an area that fails to provide them with food and water. If you know there are bats in your area and have provided a well-constructed bat house, but have had no bat tenants for 2 years, try moving the house to a new spot – especially one with more sun. If, despite all efforts, the house remains empty, it may be that bats in your area have all the roosts they require.
Bats should be considered an important visitor to any garden. Whether you actively encourage them to make your yard their home, or simply leave them to live in peace, they will reward you with their wonderful ability to purge your garden of insect pests.
Detailed instructions for builing a four-chambered nursery bat box are available on the web site of Bat Conservation International: Four-chamber Nursery House
Recognizing our Canadian bats
In Canada, 18 species of bats have been identified; eight within 50 km of Parliament Hill. Because they fly at twilight or in the dark, bats are extremely difficult to identify by sight. Sound-recording equipment is reliable for identifying only three local species, all of which are rare or uncommon. Size can be a determinant, but most experts prefer to examine them in the hand for positive identification.
All bats are medium to dark brown in colour. Local species range from the Little Brown Bat with a forearm size of 38 mm to the Hoary Bat with a forearm over 51 mm. The following species are found in our region. An asterisk marks the ones that migrate.
Occasionally bats may be seen during daylight hours; photo D. Gordon E. Robertson
- Eastern Small-footed Bat (Myotis leibii) rare
- Little Brown Bat (Myotis lucifuga) common
- Northern Long-eared Bat (Myotis septentrionalis) uncommon
- Silver-haired Bat* (Lasionycteris noctivagans) uncommon
- Northern Pipistrelle (Pipistrellus sublavus) rare
- Big Brown Bat (Eptesicus fuscus) very common
- Eastern Red Bat* (Lasiurus borealis) rare
- Hoary Bat* (Lasiurus cinereus) uncommon