Trees: The Original Bat House

roost tree

Bats in Alberta that use bat houses are typically those species that historically would have roosted in tree cavities. These cavities are most often found in old trees that have reached considerable size, and are beginning to show signs of decay. The most suitable trees are typically broken or have other structural defects, such as knot holes, woodpecker cavities, splits, cracks, and sloughing bark, which provide locations where bats can seek shelter and protection from predators. Many of these sites are also used for maternity colonies – sites where female bats come together to raise their pup. Some individual trees in Alberta have accommodated hundreds of roosting bats. In Alberta, trees most suitable for roosting appear to be large deciduous species, such as cottonwood, balsam poplar, and trembling aspen. Trees also provide important foraging habitat, and support rich insect communities needed to sustain bats.

All bat species in Alberta rely on trees for roosting and/or foraging, whereas only a few species will occupy bat houses. Therefore, the best plan for helping bats is to ensure the continued availability of bat friendly trees. Many human communities are situated along rivers or water bodies, which represent some of the most productive bat habitats in Alberta. Ensuring riparian areas remain healthy, and encouraging riparian restoration initiatives, will provide some of the greatest benefits for bats. See Planning Your Riparian Planting Project in Alberta (.pdf) for more information on restoring native riparian woodland habitat in Alberta.

In some areas, natural roosting habitat has been lost or degraded, or else trees are cut down for safety or aesthetic reasons before they become suitable for roosting. In these situations, artificial bat houses may be an appropriate option for providing alternative habitat for bats. Whenever possible, the installation of bat houses should be combined with the restoration of treed habitats. This will help ensure that alternative roosting habitat will continue to regenerate after the bat house falls into disrepair. There is much we do not know about how artificial bat houses affect our bat communities, so please consider contributing to our citizen science project.

Building and Installing a Bat House

Design Specifications

Many designs are available for building a bat house. In general, bat houses with more chambers offer a greater range of environmental conditions for bats to choose among, and should have a greater chance of being used. Multi-chambered bat houses, such as the BCI Two-chamber Rocket Box and the BCI Four-chamber Nursery House (see below), are better designed to allow bats to escape extreme daytime heat, which may lower the risk of pups dying while in the roost. Bats may regularly move roosts during the summer, so consider installing multiple bat houses and experiment with a variety of different designs and mounting options (such as different aspects or sunlight exposures).

Beware that many commercial bat houses are not optimally designed for bats in Alberta. These houses are often too small, lack multiple chambers, and are painted a colour other than black. This may result in roost conditions that are unlikely to support maternity colonies. See Building Homes for Bats for more information on suitable bat house designs.

Please read the Bat Houses in Alberta guide for recommendations on how to build and install bat houses appropriate for the Alberta climate

Also see Building Homes for Bats: A Guide for Bat Houses in British Columbia for comprehensive information on how to build and install a bat house in BC. Most information is also relevant for Alberta.

Bat Condo

Bat Condo Designs

Bat condos come the closest to replicating the high quality roosting conditions of buildings, and may be an ideal option if eviction of a large colony is planned. These designs can be quite costly, but may be an excellent project for conservation groups or companies with a keen interest in bat conservation.

Please Contact us if you are considering a bat condo project.

(Photo is of a bat condo in Creston, BC. Courtesy of the Community Bat Programs of BC)

Rocket Box

Rocket Box Bat House Designs

Offers multiple chambers and a wide range of roosting conditions needed to survive intense heat or cold. Bats can crawl to any side of the bat house, making it easy to find the right conditions for raising pups. Rocket boxes are mounted on a pole or post, and are not designed for mounting on the side of a building.

» Plans for the Bat Conservation International Two-Chamber Rocket Box (.pdf)

Multi-Chambered Bat House Picture

Multi-Chambered Bat House Designs

Multiple chambers offer a greater range of environmental conditions than single chamber designs, and are a good option for supporting maternity colonies. This is an ideal design for mounting on the side of a building (and excellent choice if you’re not concerned about bat poop), but are also suitable for pole/post mount options. Two houses can be mounted back-to-back on a single pole/post, which will allow bats to choose warmer or cooler aspects depending on weather conditions.

» Plans for the Bat Conservation International Four-Chamber Nursery House (.pdf)

Single-Chamber Bat House Designs

The easiest design, but having only a single chamber prevents bats from finding more optimal conditions during intense heat or cold. Because there is only a single chamber, mounting on the side of a building will likely be the most effective mounting option – this option effectively reduces the number of exterior walls, and helps buffer the internal roost temperature.

» Plans for the Bat Conservation International Single-Chamber Bat House (.pdf)

NOTE: Single-chambered designs are not recommended due to the increased risk of overheating. Larger, multi-chambered designs are preferred.