I remember sitting in my second grade classroom learning about how bats use echolocation to navigate. As a kid I found the story of echolocation as enchanting as any of the fairy tales that I had read. I remember running around the playground with my eyes closed hoping to discover a hidden talent for echolocation, which I painfully learned that I did not possess. I remember spending summer nights gazing up at the bats swooping around in the darkness above our house, which was located eight miles west of Cheney, Washington, a town of about 10,000 people. I remember the time a bat somehow made its way into our living room. I remember learning bat facts last summer from a park ranger in Sequoia National Park. The smallest can fit on your fingertip. The largest, called the giant golden-crowned flying fox, can have a wingspan of nearly 6 feet. Some are spotted like cows. Some drink cow’s blood. Some live off of nectar and have tongues that are up to a third of their body length long. They eat 1,000 mosquitos per hour. They will not fly into your hair.
I was lucky enough to grow up in an environment that instigated an appreciation for bats, rather than a hatred of them, although I think that most people grew up fearing bats. Perhaps it is their seemingly erratic flight patterns that cause people to believe that a nearby bat might, at any moment, go careening into their hair. Or perhaps it is the fact that they are active at night, when humans would typically be in the safety of shelter. Maybe that is what drove our neighbor boy to proudly show us the bat he had killed with his baseball bat when we were in the third grade. Maybe it is the plethora of horror stories involving vampires that gave people an irrational fear of bats. Maybe this is why, when I recently did a google search to find places to see bats in Salem, the majority of the links were either for bat removal or bat control.
I was lucky enough to grow up in an environment that instigated an appreciation for bats, rather than a hatred of them, although I think that most people grew up fearing bats. Perhaps it is their seemingly erratic flight patterns that cause people to believe that a nearby bat might, at any moment, go careening into their hair. Or perhaps it is the fact that they are active at night, when humans would typically be in the safety of shelter. Maybe that is what drove our neighbor boy to proudly show us the bat he had killed with his baseball bat when we were in the third grade. Maybe it is the plethora of horror stories involving vampires that gave people an irrational fear of bats. Maybe this is why, when I recently did a google search to find places to see bats in Salem, the majority of the links were either for bat removal or bat control.
With the fear of bats all around us I suppose it should not come as a shock that the damaging effect of our street lights on bats has received relatively little attention. As I’m sure you also learned in elementary school, bats are nocturnal, meaning that they did not evolve to be awake during the times when light is illuminating our world. Today, thanks to us, the world is illuminated 24/7. It has been hypothesized that artificial light interferes with bat’s echolocation (Buchler and Childs 1982), disrupts their circadian clocks (Erkert 1982), and subjects them to increased predation near artificial lights from predatory birds (Hartley and Hustler 1993).
In addition to the effect of artificial light on bats directly, it has had profound effects on the insects that compromise the bat’s diets. It is now commonplace for bats to feed on insects congregating around streetlights. Artificial light effects each member of the food web in a unique way, causing an intense overall disturbance in the behaviors of all living creatures. Our own scientific study this summer has been focused on the effect that artificial light has had on the behavior of mayflies. Our study will help us gain a better idea of the effect that artificial light has had on mayflies, while my own personal research will help to illuminate the complexities of how artificial light affects other areas of the food web, including human beings.
Although artificial light provides concentrated sources of food in the form of insects crowding around streetlights, the effect of artificial light on bats, as a species, is ultimately negative.
So next time you see a bat and perhaps feel a twinge of fear, think instead of the 1,000 mosquitos per hour that that bat is eating for you, and how many more mosquito bites you would have if we allowed the bats to continue their path to extinction.
Buchler, E. R., and S. B. Childs. "Use of the Post-Sunset Glow as an Orientation Cue by Big Brown Bats (Eptesicus Fuscus)." Journal of Mammalogy 63.2 (1982): 243-47. Web. 18 July 2016.
Erkert, Hans G. "Ecological Aspects of Bat Activity Rhythms." Ecology of Bats (1982): 201-42. Web.
Hartley, R., and K. Hustler. "A Less-than-annual Breeding Cycle in a Pair of African Bat Hawks Machaeramphus Alcinus." Ibis 135.4 (1993): 456-58. Web.