Bats: Migration

Summary: To migrate or not to migrate? How do bats deal with cooling temperatures? Join Kiersten as she travels through bat migration.

 

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean

 

Show Notes: 

“America’s Neighborhood Bats,” by Merlin Tuttle

“The Bats of Europe and north America,” by Wilfried Schooner and Eckard Grimmberger

“Flying-Foxes - The bush refugees” by Martin Pueschel

Backyard Bats Project: https://www.azgfd.com/wildlife-conservation/living-with-wildlife/backyard-bats-project/ 

Music written and performed by Katherine Camp

Bats: Migration

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

The fifth thing I like about bats is migration. Yes! Bats do migrate, well some bats migrate. Have you ever wondered why you see bats in the spring and summer and not in the winter? Many microbats either migrate or hibernate, while megabats may migrate from area to area following the fruiting and flowering seasons.

In this episode we will investigate the ways bats cope with colder weather in temperate regions or the non-fruiting season is tropical areas.

Let’s start with a quick definition of migration. Migration is a mass movement of living creatures from one area to another. It is often seen seasonally and can be influenced by available resources. Birds will migrate north in spring following available food resources and seeking optimum breeding grounds. They will migrate south again for the winter as the northern regions cool down diminishing food resources. Male tarantulas will migrate much shorter distances in fall searching for female mates. Bats that rely on insects can either migrate from northern regions to southern regions where the insects are still active in, or hibernate in place during the colder months of the year.

The insectivorous bat species of North America choose one of these two options. The Mexican Free-tailed bat, one of the most plentiful species in southern United States, also known as the Brazilian Free-tailed Bat, is a migrator. They will spend the warmer parts of the year in the United States traveling as far north as Northern California all the way across the country to South Carolina. Here they hunt insects at night and roost in caves or bridge overpasses during the day. They travel and roost in huge colonies and some roosts can number in the millions. It’s quite a sight to see them exit their roosts come sundown. If you are ever in an area where you can do this, do it. It is something you don’t want to miss in your lifetime.

Come colder temps in late fall when insect activity begins to slow, Mexican Free-tailed bats begin to depart. They are heading to Central and South America, following warmer temperatures. They will find caves and other enclosed spaces to spend their days until spring and summer roll around again when they will head north .

The Big Brown Bat, another insectivorous species found in North America, is a permanent resident where it is found. And they are found all over North America from Mexico to the northern border of some Canadian provinces. They are much more tolerant of colder temperatures and will hibernate as opposed to migrate. As insect activity wanes they will search for secure hibernating structures. We call these hibernaculums, and Big Brown Bats are not terribly picky. When I was researching my thesis, I found Big Brown Bats in the cave where I filmed the Tri-colored Bats. They were much closer to the entrance of the cave where temperatures were colder and less humid than the interior where the Tri-coloreds where found.

Big Browns will hibernate in groups, small or large, or as individuals in caves, abandoned or little used buildings, attics, walls, even under tree bark. They are generalists that are quite adaptable to their environment, which is why they are one of the most widespread bats in North America.

Not all migrators are insectivorous bats. The Lesser Long-nosed Bat migrates from southern Mexico to the Southwestern states of the US. They are nectar eaters and they follow the blooming flowers. They don’t come up too far into the United States but they love the flowering cactus and agave plants of the lower desert regions. They come up just after the rainy season in spring that jumpstarts the blooming season in the desert. There is actually a Community Science Project called Backyard Bats that is ongoing in Arizona with the Arizona Game and Fish Department. This project asks you to monitor your hummingbird feeders overnight to determine if nectar is going down during the night. If it is you may have visiting bats! For those of you in Arizona, I will leave a link in the show notes so you can participate in this project.

European bats have similar choices when dealing with changing temperatures. The Lesser Horseshoe Bat found in Europe is a permanent resident where they are found. They utilize hibernaculums in the winter and separate roosts in the warmer months. So, we could consider them short distance migrators. They travel only about 5 to 10 kilometers or 3 to 6 miles between the different sites. They are active during peak insect activity.

The Greater Mouse-eared Bat, an insectivorous bat found in Central Europe, is classified as a partial migrant. Partial migrants fly over 100 kilometers, or 62 miles, from winter to spring roosts. 

What about fruit-eating bats that don’t have to worry about changing seasonal temperatures? They migrate. They don’t migrate as far as some of our insectivorous friends in North America, but they still travel following food. They are a bit more like permanent residents because they stay in the same region, but they travel around that region following the blooms and fruits in trees. Most will roost together so you can see large groups of bats flying through the sky searching for ripening fruits. This movement is impacted by available food and also by the rainy season.

To migrate or not to migrate? Another amazing adaptation that makes bats even more fascinating.

Thanks for traveling with me through this episode because my fifth favorite thing about bats is migration.

  If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

 

Join me next week for another episode about bats!

 

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.