Researcher discusses the mysteries of bat migration
- 3 days ago
- 5 min read
Lisa Timpf
Advocate Contributor
When we think of migration, birds and monarch butterflies are the species that might come to mind. Though less is known about their migration patterns, bats also migrate.
Amanda Armstrong, a candidate for Master of Science in Biology and Physiology at the University of Waterloo, has conducted research at Lont Point Bird Observatory. Her studies revolved around a long-distance migrating species called the silver-haired bat.
Armstrong, who was a Harry B. Barrett Bursary recipient for 2025-26, shared some of her findings with Norfolk Nature members at the group’s speaker night on March 10.
Bats “are very under-studied,” Armstrong notes.
Unlike bird banding, which has a whole procedure that is shared among researchers, bat research is less formalized, and there’s less sharing of information. Despite these challenges, Armstrong and other researchers from University of Waterloo are trying to learn more.
Ontario has eight bat species, seven of which are classified as endangered, with the big brown bat the only one not on the endangered list. Ontario’s bats show two different migration patterns.
Five species, the big brown bat, little brown bat, eastern small-footed bat, tricolored bat, and the northern long-eared bat are regional migrants, migrating relatively short distances to hibernation sites like caves, abandoned mines, or sometimes buildings. Lowering their metabolism during hibernation enables bats to survive during the winter, when food is scarce.
The remaining three species, the hoary bat, the eastern red bat, the silver-haired bat, travel long distances to migration sites. Some of these long-distance migrants fly as far as Mexico. The long-distance travelers, Armstrong said, “tend to be fluffier” than the other bat species.
Researchers believe that’s because they fly at high altitudes, encountering colder temperatures, so the fur helps fend off the cold.
Bat species in Ontario encounter two main threats: White-Nose Syndrome and mortality from wind energy facilities. White-Nose Syndrome came to North America from Europe. This ailment, caused by a fungus, causes bats to wake up in the middle of their hibernation, depleting their energy and essentially causing them to starve. This ailment has caused bat populations to plummet.
The positive news, says Armstrong, is that bats that manage to survive a bout of White-Nose Syndrome make adaptations to help them get through any future bouts of the illness. One of these is the ability to sustain more mass.
Wind energy facilities also take a toll on migrating bats. The Canadian Wildlife Federation website notes, “it is estimated that tens of thousands of bats are killed each year in Canada by collisions, with occurrences spiking during the migration period between late summer and early fall.”
The migrating bats “are especially at risk of collisions and turbine-related barotrauma, which is tissue damage caused by sudden drops in pressure around the blades,” the website notes. The Canadian Wildlife Federation lists a number of actions that can be taken to reduce the risk of bat deaths at wind turbine sites.
Armstrong notes that while researchers can get counts of short-distance migrating bats by tallying the number in a cave or other hibernation site, long-distance migrating bats are more difficult to study.
Bats are nocturnal, and difficult to see. In addition, due to their size and physical make-up, it’s been hard to put tracking devices on them, though there have been some advances in lighter-weight trackers. Bats are also cryptic, Armstrong says, hiding in small crevices or under bark. Adding to the difficulty is the fact that bats’ migration routes vary from year to year.
Bats that migrate long distances make stopovers on their migration journey, as it’s dangerous for them to be active during the day when predators are active. Long Point makes a good place to study migrating bats because it serves as a funnel point. Bats are seeking the shortest place to cross the lake, making Long Point a natural route.
Last fall, Armstrong and other researchers were able to capture, measure, and log 140 silver-haired bats, 14 eastern red bats, and two hoary bats at Long Point.
Most of the bats Armstrong caught were youngsters. Though it’s hard to be certain why that was the case, she had a couple of possible explanations. One is that older bats may have learned that it’s possible to migrate south without crossing the lake by follow a longer route that takes them over land. Or, older bats may better able to make the crossing without stopping at Long Point.
Armstrong wanted to discover whether migrating bats forage to refuel as part of the stopover, or whether they just stop and rest. Her research confirms that bats do eat while making a rest stop.
While migration was the focus of her talk, Armstrong shared interesting facts about bats and their prey. Certain moths that taste bad to bats make clicking sounds. When a bat hears these sounds, it veers away rather than eating that particular moth. But other moths that are more savory have evolved to mimic the clicking behaviour to persuade bats to leave them off the menu.
Bats use echolocation to locate prey. In the case of silver-haired bats, high-frequency, ultrasonic sound is emitted through the mouth and taken in by the ears. But it’s not a constant, Armstrong says.
As they draw closer to prey, the sounds bats make increase in frequency, coming closer together. This increased frequency lets the bat gathers information about the object they are pursuing and pinpoint its location. Just before they reach the insect, there is a “feeding buzz” where the sounds come very close together.
Though bats are sometimes reviled or feared, Armstrong’s talk portrayed bats as fascinating creatures. By helping to control insects, bats have an important role to play in ecosystems.
They are also helpful to humans, consuming insects like mosquitoes, or “pest” insects that harm crops. Though there is still much to learn about bats’ migration behaviour, the work of Armstrong and other researchers is bringing important information to light.
One of Armstrong’s fellow researchers discovered that migrating bats seek out clusters of trees, and gravitate to the tallest of these trees when it’s time to sleep. Though silver-haired bats, as solitary creatures, don’t migrate in groups, bats stopping in the same area all will be drawn to the tallest tree, meaning several bats might be found together.
Bats can see groupings of trees from the high altitudes where they are flying during migration. In the long term, knowledge about preferred stopover habitat may help researchers identify habitat that should be preserved.
Norfolk Nature offers a number of nature-related talks and field events free of charge. Details about upcoming events can be found at their web site, https://norfolknature.org/
Comments