I have researched maternal colonies of northern long-eared bats (Myotis septentrionalis) on and off since 2017. I am fascinated with the roost-switching process in particular. Maternal females give birth and raise their pups in tree cavities, but they don’t just stick to one for the entire summer–they move almost daily, even while their pups are totally dependent on them and unable to fly.
So I knew that bats carry their pups somehow, even before I started monitoring these trees with cameras for my graduate research. The concept is already difficult. Bats can be born already weighing a third of their mother’s size, an extreme burden on any animal, let alone a flying one. Besides, bats don’t have much surface area to grip onto. Even though we know that they must do it, I wanted to see it for myself to understand better.
Seeing microbats carrying their young is practically impossible. They move at night and switch to new roosts as far as a kilometer away. I know that northern long-eared bats tend to use the same roost trees each year, though, even if we can’t predict exactly which one they will move to. So I decided to install game cameras at tree cavities that the bats had used before and set them to record during the summers of 2020 and 2021. My expectations were low: I suspected that recording fast-moving objects at night wouldn’t result in video quality high enough to see pups, but I wanted to record bat use of the tree cavities throughout the summer.
Camera 8 was a high activity site, and recorded bats using the cavity in 2020. But week after week in 2021, I returned to maintain the camera. The angle was wrong, or nothing triggered the camera. Perhaps the bats had abandoned that tree.
In the middle of July, I downloaded the latest batch of videos and saw the tiny thumbnails generated for each video. Holy cow, we recorded a lot of bats! In the first video I opened at random, something strange was up. Did the bats look lumpy? I slowed the video to 1/10th speed and couldn’t believe it. The lumps were unmistakably bat pups.
The quality was much better than I could have imagined. The pups appear to be hanging on by biting onto the mother’s nipple. With only one gripping point, it looks to be a very bumpy ride. And these bats sometimes carry their pups in this manner as far as a kilometer between trees!
I love researching bats because they continually surprise me. The more I learn, the more questions I have. How do they coordinate movements of entire colony of 50+ animals? How do they choose where they will go next?
Maybe I’ll have the opportunity to find out more someday–after all, I never thought I would get to see them carrying pups before now.