Canadian Bat Box Project

Karen Vanderwolf with Trent University is leading a national bat box project in Canada in partnership with the Wildlife Conservation Society and the Canadian Wildlife Federation. There is very little information in the literature on bat boxes in Canada and which box designs are best for our northern climate. However, there are existing unpublished datasets on bat box usage and microclimate in several provinces. They plan to assemble existing datasets and generate new data into a peer-reviewed publication.

European studies indicate the preferred interior shape and volume of bat boxes varies by species, but this has never been examined in Canada. Of the 18 species of bats that regularly occur in Canada, 13 have been documented using bat boxes in the United States. Little is known about what bat species use bat boxes in Canada. Myotis yumanensis, Eptesicus fuscus, and M. lucifugus are known to use bat boxes to raise their young in Canada, and Lasiurus borealis has been sporadically reported roosting in boxes.

Little brown myotis emerging from a bat box (photo compilation) – by Jordi Segers

For heterothermic bats that live in cold climates, such as Canada, roosts with a warm microclimate are important because juvenile growth is dependent on roost temperature, both during gestation and lactation. Consequently, many bat box recommendations in Canada are designed to increase interior temperatures by painting boxes dark colors and mounting boxes in locations that maximize sun exposure. However, as in Europe, there is increasing concern in Canada that bat boxes can overheat, potentially leading to bat mortality.

The overarching goal of the study is to gather data on what types of bat boxes people in Canada are currently using (styles, dimensions, # chambers, mounting conditions, etc.), the microclimates of different boxes, and determine the number of bats of what species use boxes to answer the following main questions:

1. Which bat species in Canada use bat boxes to roost in and which species use boxes to raise pups?
2. Do different bat species in Canada prefer different types of bat boxes/box microclimates/box mounting conditions? Are there regional differences?
3. Do bat boxes overheat in Canada (>40 ºC) and if so, what styles of bat box overheat under what mounting conditions in which regions?
4. Is there mortality from overheating bat boxes across Canada?

Since this project has a national scope, it will rely heavily on citizen science and regional collaborators. Participants will be recruited from batwatch.ca, existing provincial community bat programs, local bat researchers, naturalists clubs, Parks Canada, and through promotion of the project in the media. Citizen scientists are asked to fill out an online survey (multiple choice questions about their boxes) and conduct emergence counts in summers 2021 and 2022. Further participation includes installing a microclimate logger and collecting guano for species identification and other research. The survey is here and can be viewed in English or French.

Hot bat box temperatures can be documented with loggers, but this does not indicate what effect these temperatures have on bats. As part of the bat count (emergence counts) protocol, citizen scientists are asked to examine their boxes during the day on hot days to see if bats ‘bulge’ out the bottom or if bats are outside the box or on the ground (dead or alive).

Determining if bats are reproducing in bat boxes requires assessing bats in-hand for evidence of pregnancy or lactation and cannot be done by citizen scientists. Therefore, assessing reproduction in bat boxes must be done by trained biologists. Given the national scale of the project, this will be possible for only a subset of bat boxes. Fieldwork is planned, if possible, in summers 2021 and 2022 although citizen scientists will be able to monitor boxes in their backyards and collect microclimate data regardless of lockdowns.

If you know anyone with a bat box, regardless of whether the box is known to have bats, please encourage them to fill out our survey. If you have an existing unpublished dataset or wish to collaborate with us on this project, please contact Karen Vanderwolf at kjvanderw@gmail.com

For more details, visit the project webpage.

Little brown myotis roosting in a bat box – photo by Jordi Segers

Submitted by Karen Vanderwolf, PhD candidate, Trent University.

This guest blog is part of our Bat Monthly newsletter of October 2020. Click here to read the full newsletter.