There are numerous styles of bat-houses on the market and not all of them are designed for BC. Some factors influencing the success of these designs are related to factors like size, vents, landing strip, etc. (as follows). Other factors to consider when selecting a style are cost, space available on your property, size of the bat colony (if bats are already present), and location options.
For detailed information on bat houses, see Building Homes for Bats: A Guide for Bat Houses in British Columbia
The most common bat-house is a bat-box. Bat-boxes are tall, rectangular compartments with at least one chamber, a landing strip, and an open bottom. Small bat-boxes are usually 40 cm wide and 60 cm high. They have only one chamber, providing a roost space for up to 50 bats. They do not support large colonies and must be mounted on a building. You can download plans to build a single-chambered bat-house here: Single chamber bat box.
The multiple-chambered (nursery) boxes offer more roosting space and the ability of bats to move with changes in temperature. Multiple-chambered bat boxes can hold over 200 bats, and are a more successful design for BC. A good set-up, especially for a large colony of bats, is to put two multi-chambered bat boxes back to back on a post. Designs for a multi-chambered bat-house can be downloaded here: Four chambered nursery bat box.
Rocket boxes are very successful. They are usually 1 m tall, and contain concentric roosting chambers of 20 mm (3/4”) around a 4” by 4” post. By increasing the number of square roosting chambers, the rocket box becomes wider and can house more bats. This bat-house style is usually built around a post, so installation simply requires fixing the post in the ground. These structures can also be adapted to be put on buildings. This bat-house style has been extremely successful on the coast of BC, especially for Yuma myotis, a common urban bat species. For plans on how to built a rocket box look here: Two-chambered rocket box plan.A simple rocket box design is built from a 4" by 4" post that has a wooden box over it. This design is easy to build and relatively cheap for materials. The success rate for this design in the Kootenays has not yet been determined. Let us know! Download the simple rocket box design here: Simple rocket box bat-house plan.
UNCLE GEORGE DESIGN
A relatively new “Uncle George design” is being experimented with in Oregon. This design has slats at various angles, rather than just vertically as in a typical nursery box. A study in Washington found that this design attracted bats more quickly than nursery boxes or rocket boxes. To date, however, no maternity colonies have occupied this bat house. If you’d like to try building this design, please let us know so we can work together to modify it for our area. Click here for box plans or click here to purchase
Bat condos and mini-condos are large structures that can potentially house thousands of bats. They are costly and time consuming to build but can house large colonies of bats (more than 6,000 in a fulls-sized condo). Bat condos can be considered when there are large bat colonies being evicted from a building, for wildlife and restoration projects, and for increased insect control. If you are considering building a bat condo, contact your local community bat program to discuss options.
There are many different designs, including ‘mini condos’, and ‘bat motels’. You can find basic mini-condo plans here. In BC, where climate is colder, the designs should be modified to partially close chambers to trap air and thus increase roosting temperatures. Decreasing gap size between roosting boards will also help trap warm moist air when bats are roosting as a group. Additionally, creating purposeful gaps between exterior boards or planks during construction can increase the variety of microclimates created for bats in the structure. Some modifications used in Kitimat can be found here (simple, modified).
There is still much to learn about successful bats houses in BC. Try experimenting by putting bat-houses in different locations, or staining one and not the other. Please share the information with us about what worked and what didn’t. Better yet, register your bat-house and be part of our interesting and valuable research. Remember, it is just as important to report bat-houses that were not successful in attracting bats as those that were.
A volunteer builds a 4 Chambered Maternity Colony box A "Rocket Box" type bat house