While there has been substantial work conducted on Little Brown bat (Myotis lucifugus) maternity colonies, there is a lack of research on females inhabiting the Canadian portion of the Rocky Mountains. The environment is challenging as colder, wetter nights and a shorter summer season reduce prey availability while increasing energetic costs. I therefore hypothesized that reproductive females would reduce their energy expenditure (torpor, movement and roost switching) and/or energy intake would increase (multiple foraging bouts, foraging during sub-optimal conditions). I identified reproductive timing, use of torpor, and movement of females in a large (n=700+) maternity colony located around the Kananaskis Lakes. For reproductive individuals, I predicted that compared to lower elevation populations: gestation would be longer, distance travelled between roosts would be shorter, roost switching would be more frequent and bats would use consistent, short torpor bouts. To accomplish this, I caught individuals and attached 29 temperature-sensitive radio transmitters to adult females from May to August 2021, noting their reproductive status (Pregnant, Lactating, Post-Lactating, Non-Reproductive). I recorded tagged individuals’ presence and skin temperature, and recorded bat box temperatures. Day-roosts were located by following tagged females, and nightly emergence was conducted multiple times a week to record changes in colony size.
Results/Conclusions
From the main roost, three bat boxes located at the Peter Lougheed Discovery Centre, females consistently emerged before sunset and in inclement weather (sleet and rain) with multiple foraging bouts during the night. Confirmed day roosts included buildings, bat boxes and rock faces, with similar frequencies of roost switching in the various reproductive groups. The majority of females' day roosts were within a 5km range throughout the season. The estimated gestation time was between 59 and 82 days. This is longer than the 50-60 average for the species but is similar to the 49-89 days of females in the mountains of Yellowstone National Park. While there was no significant difference between reproductive stages in the amount of torpor used per day, pregnant females did not spend more than 29% (n=4) while non-reproductive females spent as much as 99% of the day in torpor (n=11). These data provide insights into the additional challenges reproductive female Little Brown bats face in the Rocky Mountains and confirm my predictions regarding an extended gestation period and foraging behaviour. It also highlights the importance of buildings in the mountains as alternate roosts and their potential in sustaining populations.
