Recent observations suggest possible problems associated with bat houses, and a need to revisit how to help bats out with artificial roost structures.
In fact, existing approaches may only meet some of the varied needs of bats and could, in some cases, be unsafe for bats in an era of a rapidly warming climate. In light of climate change, are batboxes actually getting too hot and creating habitat sinks rather than benefiting bats?
Installation of bat boxes is frequently suggested by bat conservation groups as a conservation or enhancement tool for citizens wishing to assist bat populations. However, it is unknown if boxes are beneficial or detrimental to local bat populations. It is possible that these small, isolated roost structures may be counter-productive to conservation and recovery efforts, especially if they do not provide an appropriate range of microclimates for maternity colonies and could thus lead to mortalities or lower reproductive success.
The Project:
Goals and Objectives:
1. To investigate roosting ecology and the characteristics of building versus box roosts. Specifically, we will quantify the reproductive success for Little Brown Myotis and Yuma Myotis in buildings and bat boxes, and document microclimates offered in these structures. We will also examine the use of satellite roosts (roost switching behaviour) to determine if this plays an important role in bat box occupancy during extreme ambient temperatures, and whether heat-stress related mortalities or behaviours are observed.
2. Through partnerships and collaborations develop a continental guidance document for use of bat boxes in North America. Specifically, WCS Canada has been asked to develop the US-Canada Bat Box Best Management Practices for the two countries’ WNS Conservation and Recovery Working Groups.
Methodology & activities:
We will compare roosts within and among two study areas which differ in habitat and thus climate. The Okanagan region of B.C. is a dry, hot climate, and the Kootenay region of B.C. has a moister, more moderate climate. Our objectives are to: 1) characterize roost use; 2) describe temperature and humidity profiles at roost sites and; 3) compare reproductive success based on roost type for focal taxa, in two different types of roosts (buildings, and box roosts). There is growing popularity of bat ‘condos’ and ‘mini-condos’ in B.C., thus we will additionally describe microclimate profiles of ‘bat condos’ and compare to building and bat box roosts to determine whether condo designs may represent a more appropriate mitigation option for bat population recovery than bat boxes.
To develop the international Bat Box BMP, we will partner with Canadian Wildlife Health Cooperative (CWHC), and recruit other experts in the field for a ‘Bat Box BMP Development Committee’. This international committee will compile literature, published and grey, and guide upcoming research efforts to fill critical knowledge gaps about bat boxes that will be needed to underpin science-based recommendations.
We will document roost switching of focal taxa by radio-tracking individuals from known maternity colony sites (building roost and box roost). This will enable us to determine what roosting options exist for bats at our study sites and follow their roost selections throughout the reproductive season. Data loggers will be deployed at focal sites to record micro-climate conditions within each roost type as well as ambient conditions. Roosts will be thoroughly described including size, orientation, structural design, and surrounding habitat. Occupancy monitors (custom-made) have already been designed and tested by WCS Canada, and are currently deployed at select sites in B.C., allowing roost occupancy to be overlaid with microclimate profiles.
Existing data from Annual Bat Counts (by B.C. Community Bat Regional Programs) will be included in the investigation of roost characteristics, colony trend, and reproductive success. We will capture bats at strategic times throughout the reproductive season to determine the timing of parturition, percentage of adult females successfully raising a pup, and how quickly pups grow to adult size. We will use capture data from a minimum of two field sessions per year to assess reproductive success for focal taxa as it relates to roost type. Capture data and roost counts will be supplemented with use of acoustic roostloggers which will provide continuous monitoring of activity levels throughout each night of the reproductive season, quantifying activity patterns for determining roost use, lactation, fledging, etc.
To specifically examine whether bats experience heat stress, we will collect guano samples from bat boxes and building roosts throughout the summer and particularly during periods of extreme temperatures. These samples will be analyzed by University of Saskatchewan (collaborator Dr. Vikram Misra) to determine the relative number of viruses that are shed by roosting bats (boxes vs. buildings) when exposed to varying roost microclimates and specifically in bat boxes when temperatures may exceed that of those in building roosts.
Progress to Date:
Susan Dulc, MSc student at Thompson Rivers University under the supervision of Dr. Karl Larsen and adjunct professor Dr. Cori Lausen, has one field season so far (2019) and has collected valuable information about bats roosting in bat boxes versus buildings. After one more field season she will be in a position to compare and contrast reproductive success, roost microclimates, heat stress events, parasite loads, and more.
Results are anticipated to be applicable at local, regional, and national levels to inform population recovery actions. In particular, these results will underpin some of the recommendations in the international Bat Box BMP. To date there are more than 50 biologists who have joined the international committee to develop this guidance document.
Funders and Collaborators:
This project is made possible by the generous funding from the US Fish and Wildlife Service, Environment Canada-Habitat Stewardship Program, Regional District of Central Kootenay-Kootenay Lake Local Conservation Fund, and Edmonton Community Foundation.
Partners in this project include: Thompson Rivers University (Dr. Karl Larsen) with MSc. student Susan Dulc, University of Saskatchewan (Dr. Vikram Misra), , BC Government (Dr. Leigh Anne Isaac, Dr. Glenna McGregor), and the Canadian Wildlife Health Cooperative (Jordi Segers).
We thank Emily deFreitas for spearheading the BMP data collection efforts, and to the many people who have already contributed data and time to the development of the BMP.
Links to Articles and Webinars:
Hot houses: the race to save bats from overheating as temperatures rise. February 24, 2021. The Guardian.
What's the Best Way to Welcome Bats to the Neighborhood? The Goldilocks Approach. September, 2019. The Relevator.
Roosts for Tomorrow. November, 2019. Canadian Wildlife Health Cooperative Webinar.
Bat Boxes: Back to Basics. March 2020. Kootenay Conservation Program Webinar.
The Goldilocks Approach: Use of Bat Boxes in a Changing Landscape and Environment. October 2020. Bat Matters Conference 2020.
Buildings vs. Bat Boxes. June 2021. Conference Poster. WNS National Webinar, USFWS.