Bat Boxes

Bat boxes can be a great way to help out your local bats! They can provide needed roosts in areas where there are none, they can attract helpful, insect eating bats to the community, and they can be great educational tools. Bat boxes however can be tricky. One commonly repeated story is about the bat house that has remained unused for years. This can be discouraging and may put you off conservation all together. There are numerous reasons why a bat box may go unused but likely, it’s simply that the box does not meet the roosting requirements for the local species and the bats are choosing to roost elsewhere. Most species have very specific conditions they need for roosting and different bat box designs will provide different conditions that will be favored by different species. What may be good for one species in a certain area may not be good for different species or even the same species in a different area. Bats in the south and other hot dry areas are typically looking for areas that will keep them cool in a hot area. Bats on BC’s coastal region will typically be looking for roosts that will keep them warm and dry in a wet, cold area. Bat boxes designed with southern and eastern US bat species in mind may not provide BC’s bats with the requirements they need. More research is emerging comparing different bat box designs that may be more suitable for bats in BC’s south coast region.

The ‘Nursery Box’
The nursery box is one of the most commonly available bat house designs. Also sometimes known as a mammoth box, for the variation tested at Mammoth Cave National Park, this bat box is an chambered box that is open at the bottom. Inside the box, vertical slats give bats a place to roost and different sized boxes can be used to accommodate larger or smaller numbers of bats. These boxes are the cheapest and simplest to build with plans freely available on the web (including our Links & Resources section). Nursery boxes are also the lowest priced and most commonly available bat boxes for purchase online. Recent research conducted in Washington state and BC have found that the nursery design is not the most effective bat box for the region and recommends either modifying the design of your nursery house to make it more suitable for Pacific Coast bats or using an alternative bat box design.

The ‘Rocket Box’
The ‘rocket box’ is a bat box designed and tested by Dan Dourson and John Macgregor in the Daniel Boone National Forest in eastern Kentucky. The original design for the box was a tall covered box that fit over a wooden pole. The design worked well because it allowed the the bats to move about freely within the structure to cooler or warmer areas, depending on preference. The design proved to have a high success rate and has since become popular to install in Kentucky and elsewhere in North America. The design has since been expanded to add a second chamber on the outside (doubling the capacity) and has proven to be very successful (.pdf) during recent testing in the pacific coast region compared to nursery boxes.

The ‘Uncle George’
The ‘Uncle George’ slatted bat box is a more recent design created by Greg Falxa (Cascadia Research), “Uncle George” Carlson, and Sanders Freed. The Uncle George differs from the previous two designs in that rather than having a singular open bottom cavity for bats to enter, it instead has an open ‘slatted’ face designed to mimic peeling bark or loose building shingles. The creators and authors of the Cascadia Research study in Fort Louis, Washington believe the Uncle George boxes may be more ‘acoustically attractive to bats’ and recommend ‘installing them alongside the larger rocket boxes to speed discovery and usage’. The Uncle George box had a very high success rate during the study (65% overall total usage compared to 45% for dual chambered rocked boxes and 10% for the mammoth boxes) and looks like a promising design choice for use in BC’s south coast. The cost of the Uncle George design falls midway between the dual chambered rocket box and the mammoth box.

Other Designs

Many different bat box designs exist and as bats are very adaptable and resourceful animals all manner of structures have been known to be used as bat roosts. These designs have varying success to cost ratios and may not be the most practical choice. But if you’re really enthusiastic about bats these may be what you’re looking for.

The Bat Condo can probably be best described as a miniature barn on stilts. The bat condo is open on both sides to allow bats to enter from either side and it is spacious enough to hold more than 6,000 mother bats and their young. It was designed specifically for housing little brown myotis maternity colonies but its size and price may be too much for most except the battiest bat lover.

This interesting design combines a nursery style bat box with a bird house. This is perfect for the nature enthusiast who likes to provide habitat to many species but may not have much space.

These suburban bat house designs are intended for excluding bats from a home in the suburbs while providing an alternative roosting site.

Mounting the Bat Box
While design may play a key role in whether a bat box will be used or not, how and where a bat box is mounted can also greatly affect whether a box will be used. Bat boxes in BC’s south coast need to provide warmth for roosting bats so it’s recommended that bat boxes be a dark colour or black and that they are south facing to absorb the maximum amount of sunlight. Bat boxes also need to be mounted high. A common problem with many bat boxes is that they are not mounted high enough. The minimum recommended hight for mounting bat boxes is 3.7 metres (12′) and higher is even better. Another way is to mount a bat box nearby to an entrance way where bats are being excluded from before sealing the entrance. With some luck if the bat box is similar enough to its previous roost the bats will move to the house. Bats are very good at finding places to roost and are very picky about where they roost. Researching the needs of the species you’re trying to attract, choosing a proper design and mounting your box in the correct location are crucial if you want your bat box to be used. Remember though an empty bat box can be just as important for the course of bat research as a lived in one. But following these guidelines can help you get the most out of your bat box!