Living with the Big Brown Bat

Jasmin Rubinic

Instructor: Michael Grattan

English Composition

                          Living with the Big Brown Bat (Eptesicus Fuscus)

When the sun goes down and the day slowly ends, they come out and fill the sky – bats. Some people don’t mind them and even enjoy watching them dancing high up in the sky, while others get uncomfortable and scared. Bats have been around for a long time, and for some reason, we humans seem to be fascinated by them. We write stories and make movies about them and even created a bat superhero! As long as bats are far away, they are tolerated. But what happens when they come to live either on the inside or on the outside of our homes? All of a sudden, the previous fascination turns into panic and disgust. Species like the Big Brown Bat seem to prefer human build structures as their roosting location and, once they moved in, they are not easy to get rid of. When I discovered that a maternity colony of Big Brown Bats picked our house as their new home, I became curious and started to wonder if they would pose any kind of harm to me and my family. In order to make the decision to either evict them from our attic or let them stay, I started to read about these animals.  Research suggests that Big Brown Bats not only prefer and benefit from living in human built structures, but humans can benefit from living with bats as well.  

Just the thought of having bats living in the same building is not comforting for many people. We are under the assumption that bats will attack us, get tangled in our hair, expose us to diseases and even bite us to get our blood. What most people don’t realize is that the majority of bats native to the United States are insectivores. This means that they exclusively eat insects, and have no desire to go after our blood. In fact, there are only three species in Latin America that are “vampires”, but we will come to those later. The main reason that these animals are so misunderstood by most of us is because we don’t take the time to learn more about them.  On the website of the National Park Service of New Mexico, bats are described as warm- blooded mammals.  They give birth to live young called pups. They don’t have feathers but fur, and they, just like us humans, breast feed their young (National Park Service, New Mexico). Bat Conservation International states on their website, batcon.org, that there are over 1200 species of bats, which makes up one fifth of all mammal species. The diversity is incredible: While the flying fox can get a wing span of 6 feet, the smallest bat, the bumblebee bat, weighs less than a penny.

     Bats have many traits that are beneficial to humans as well as to nature itself, but they can also pose a risk to humans. While the benefits will be discussed later on, the risks can’t be left out. Humans might feel that bats are a threat due to the diseases they might carry and there are, indeed, multiple fatal diseases that can be associated to bats in general. The Centers for Disease Control and Prevention caution humans not to handle bats, due to several risks involved. The best known disease carried by bats is rabies. This deadly disease can be transmitted by a bite of a rabid bat or when the animal’s saliva comes in contact with a human’s mouth, eyes, nose or a fresh would. Another dangerous disease transmitted by bats that can be found on the The Centers for Disease Control and Prevention’s website:  Histoplasmosis. This disease usually affects the lungs and has no other apparent symptoms. It is caused by fungal spores that occur in soil that is exposed to guano, or bat droppings. (The Centers for Disease Control and Prevention).  Even though this might appear concerning to most of us, bats have more benefits than they cause harm.

     Now that we have the basics of the bat covered, we should focus our attention on the Big Brown Bat, or Eptesicus Fuscus. This species ranges from northern Canada to Mexico, and can be found in various habitats, such as wooded areas, low land deserts and forests. With a wing span of 12-16 inches and an average weight of 0.5 – 1.2 ounces, the Big Brown Bat is considered one of the larger bat species in the United States. Their fur color ranges from brown to copper with their belly being lighter than the rest of the body.  Their ears are small and rounded and, just like their wings are black in color. The Big Brown Bat can reach speeds of up to 40 mph when flying and can live up to 18 – 20 years (Desert Museum).

Due to us humans slowly but steadily taking over the natural habitat of bats, today, the Big Brown Bat can be mostly found in human build structures, such as barns, bridges and houses, instead of hollow trees and natural caves.  A study on the roosting behavior of Big Brown Bats, conducted by Corey Lausen and Roberts Barclay, and published in the Journal of Mammalogy, suggests that Bats prefer roosting in human built structures.

 This study was conducted on three maternity colonies of big brown bats (Eptesicus fuscus) in southeastern Alberta and focusses on the benefits of living in a building. All three colonies roosted in different structures ranging from buildings to natural roosts. During pregnancy, bats roosting in buildings were more active, which translates into more active days for fetal development. It was observed that bats roosting in buildings gave birth earlier than bats roosting in rock crevices. During the study, predators, such as owls, raccoons and snakes were observed in the rock roosts, but not in the building roosts. This suggested that rock roosting bats need use shallower torpor (a state of not being active). Bats roosting in buildings are believed to use less energy while due to the warmer environment and achieve lover body temperatures in colder weather. The study concludes on the proposition that the overall advantages of living in a building, compared to natural roosts, lead to long term success in reproduction (Barclay, Lausen).

Bats living in buildings are usually not invasive and disappear after the pups are old enough to fly. Unlike mice and other rodents, bats cannot chew and are not as destructive. If kept out of living spaces of houses, the bat can be more beneficial than harmful.  A study conducted by Agosta Salvator and David Morton, focusses on the diet of the Big Brown Bat.  

This study was conducted on three maternity colonies in Pennsylvania and Western Maryland. Using fecal samples from different colonies, the researchers determined that there are variations in the diets among the three maternity colonies, depending on the location they were living, as well as temporal variations within the maternity groups. The found data was compared with data previously collected from a maternity colony in Indiana. The results were overall similar, showing beetles as the main food source.