Welcome to the end of Spooky Season! With all of the Halloween decorations that have bats in them, I thought that this would be a great time to talk about these amazing creatures. While all of the species of bats that live in MN are insectivores, bats are also excellent pollinators and seed dispersers world wide. Often given a bad reputation in stories, shows, and movies, bats are wonderful members of their biotic community. Without them, we would have more insects, less fruit, and less flowering plants.
Bats are the most numerous mammals after rodents, composing an estimated 20% of the worldwide mammal population. They are the only mammals capable of true flight (as opposed to gliding) thanks to highly modified hands. Bat wings are more flexible than bird wings, allowing them to be very agile fliers. They live 3.5 times longer than other mammals of similar size and bat sizes cover an impressively wide range. The smallest bat in the world, Kitti’s Hog-nosed Bat, is about the size and weight of a bumblebee. The largest bat in the world, the Golden Crowned Flying Fox, weighs 3.5 pounds and has a wingspan of 5’7”.
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Bats have one pregnancy a year, usually birthing a single pup. Birthing is done in a horizontal or head up position so that gravity can assist with the delivery. The pup can be up to 40% of the mother’s body weight at birth. The pelvic girdle is attached by a ligament allowing it to expand to accommodate the pup. Pups are born rear-end first and then are cradled by the mother in her wing and tail membranes. Some scientists speculate that this prevents the wings getting tangled during birth.
Bat populations are in decline worldwide due to habitat loss and the rise of disease. Climate change is also affecting bats, with changing temperatures resulting in populations leaving previous ranges to move to more hospitable ones. Evening Bats, which were previously thought to only live as far north as Illinois, have been found moving steadily north into MN and were found in Ramsey County in 2016. (https://www.dnr.state.mn.us/mammals/bats.html)
The Big Brown Bat is the most common species of bat found in MN. They commonly roost in buildings in the Summer and will return to these roosts year after year. These seasonal roosts are referred to as maternity roosts or maternity sites. Big Brown Bats are often seen in urban areas roosting in buildings, barns, bridges, bat boxes, and tree cavities. They are the only bats in MN who can hibernate in buildings, but will also overwinter in caves and mines. While Big Brown Bats are susceptible to White Nose Syndrome, it has not affected their population as much as other MN bats. White Nose Syndrome has devastated some of our state’s bat populations.
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White Nose Syndrome is caused by the fungus Pseudogymnoascus destructans, or Pd for short. (https://www.whitenosesyndrome.org/static-page/what-is-white-nose-syndrome) This fungus prefers to grow in cold, moist places. The overwintering sites for many North American bats fit these criteria very well. When the fungus infects a colony it will grow on the faces and exposed (not furry) parts of the body. This is very irritating to the bat and results in them coming out of hibernation early as their body temperature rises to fight off the fungus. The higher body temperature burns off their food reserves that they need to survive the winter. The bats are often unable to re-enter hibernation and are observed engaging in erratic behavior. This erratic behavior has led to the name White Nose Syndrome. For more information on White Nose Syndrome and the fungus that causes it, please visit the White-Nose Syndrome Response Team website at https://www.whitenosesyndrome.org/. I strongly encourage you to educate yourself on White Nose Syndrome prevention to help protect our bats the next time you visit a cave, mine, or other known roosting site.
I hope that you have enjoyed learning about bats! While they are tucked away for hibernation now (or they soon will be), these wonderful creatures will grace our skies again in the Spring once the insects return. Have a great day, and Happy Halloween!