Monitoring Mysterious Mammals: Meet TRCA’s Bat Team

Under the cover of darkness, Toronto and Region Conservation Authority (TRCA) records bat echolocation calls using specialized devices that can “hear” the high-frequency sounds that bats emit for navigation.

little brown bat — Eastern Red Bat, one of eight bat species found in Ontario.

This detective work occurs in June and July, overlapping the breeding periods of eight Ontario bat species.

During this short window, biologists from TRCA’s Terrestrial Monitoring team must work swiftly and efficiently to deploy recording devices at multiple locations across the Toronto region.

This effort is a race against time, as the team must complete breeding bird surveys occurring simultaneously.

TRCA biologist sets up a bat meter, or Autonomous Recording Unit, high up in the trees in an area believed to be suitable for bat roosting (i.e. where they sleep during the day). Bats like to roost in larger trees with peeling bark, holes, or cracks that are located near water. Locations such as these can provide ample hunting opportunities for mosquitos, beetles, moths, and other night-flying insects. These bat meters record bat echolocation sounds for approximately 10 days before the data is downloaded for analysis.

Analyzing the Data

The valuable information gained about these mysterious mammals is worth the hustle. Since 2017, TRCA has been capturing bat echolocation sounds across the jurisdiction to gain insights into where and when different bat species are present, and to understand their general ecology.

With training and support from the Toronto Zoo, TRCA has developed the technical expertise necessary to analyze this data, allowing for a better understanding of bats in the Toronto region.

Our goal for the 2024 field season was to continue filling data gaps in areas where monitoring had not previously been conducted.

spectogram displaying visual pattern of bat calls — The unique visual pattern of bat calls, as seen in spectrograms, help to identify different bat species. The visual above is of the Big Brown Bat. Registrations are the individual calls the recorders pick up. This means it could be one individual flying back and forth producing many calls, or multiple bats of the same species making just a few calls. The recorders can’t tell us how many bats are in the area, but they can confirm the presence or absence of species.

Understanding Bat Presence in the Toronto Region

Before collecting this data, little was known about bats in Toronto region.

We only knew that some, such as Big Brown Bat and the Myotis species, spend their entire life cycle in Southern Ontario, while others, such as the Eastern Red, Silver-haired, and Hoary breed within the region but migrate south in the fall.

Threats to Bats

Bats in Ontario face numerous threats, with four of the eight species listed as endangered.

Habitat loss due to the destruction of mature forests that are used for roosting (shelter) and raising young, along with wetlands for foraging, pose the most significant risk.

Additionally, white-nosed syndrome – a fungal disease spreading among bats in North America, along with slow reproduction rates and the impact of wind turbines, further endanger these species. Learn more.

Surprising Discoveries

TRCA’s monitoring efforts have yielded some surprising findings.

For example, Hoary and Silver-haired Bats are more prevalent in the Toronto region than previously thought, especially in urban or urbanizing areas.

Furthermore, the endangered Eastern Small-footed Myotis Bat was discovered in the northern reaches of the Humber River watershed.

The only bat species not yet found during TRCA surveys is the Tri-coloured Bat, although this species has been documented by the Toronto Zoo in Rouge National Urban Park.

graphic illustrating the bat species found by TRCA bat monitors over the last five years — This graphic illustrates that Big Brown Bats are the most common species found throughout Toronto region, although it is considered a Species of Urban Concern, meaning it occurs throughout the region but could show declines if urban impacts are not mitigated effectively. Bats generally tend to be more present in the more rural, undeveloped areas of our regional landscape – however, it is good news to see that many species persist in the more urbanized areas.

Thanks to the expanded dataset, TRCA has applied local conservation ranks and scores for the first time to regional bat species, with seven of the eight species now ranked as Regional Species of Conservation Concern.

This proactive approach aims to alert conservation managers to potential local species declines and losses in the future, guiding conservation and management decisions.

Continuous long-term monitoring will assist TRCA in updating the status of regional bat species over time.

Monitoring Built Bat Boxes

TRCA is also making a difference by creating suitable homes for bats to breed and raise their young through habitat restoration, including installing bat rocket boxes.

These boxes provide alternate roosting sites in the absence of mature trees. The monitoring of these bat boxes involves nightly checks throughout the summer to assess occupancy and the condition of the boxes.

Data collected from these efforts will help determine the success of bat boxes in supporting local bat populations and inform future habitat restoration initiatives.

The box design includes two sections that bats can easily move between to find their preferred temperature throughout the day. Inside ledges also allows for plenty of places to roost.

The box is made of pine and painted black to help maintain the right temperatures.

The video below is an example of a spacious bat box, which can accommodate up to 200 roosting Little Brown Bats. This is the only known occurrence so far, but we hope the rocket boxes become more popular with the bat community.

How You Can Help

Bats play a key role in our ecosystem by controlling insect populations, which helps to protect crops and forests. Here’s how you can contribute to bat conservation:

Read the Toronto Zoo Bat Conservation Guide.

Follow the Canadian Wildlife Federation’s instructions for building a bat box on your property.

If you’re a teacher, sign up your class for TRCA’s Bat Program at Lake St. George Field Centre.

Check out local events for Bat Week (October 24 to 31)!

Learn More

Stay Connected

Scientific data collection and research informs decisions affecting the natural areas and watercourses within our region. Connect with TRCA online.