Leslie Sturges, president of Bat Conservation & Rescue of Virginia, organized a bat count on the evening of July 27 at the farm of Carolyn Ford, just within Staunton city limits. We had excellent attendance and weather, with a total of about 17 participants, including three from our Headwaters Master Naturalist chapter.
We began with a brief survey of the barn whose floor held an abundance of bat droppings, promising an impressive turnout of bats. It in fact houses a sizable number of female big brown bats (Eptesicus fuscus) in a bat maternity colony. Leslie gave a roughly 15 minute presentation as we waited for it to darken sufficiently for the bats to emerge. We then stationed ourselves at strategic points around the barn to watch as they shot out of various openings, silhouetted against the evening sky.
We got to use various electronic devices to render audible the ultrasonic emissions of the bats. I received a handheld device called a ‘Baton,’ which reduces the frequency by a factor of 10 such that an inaudible 30 kilohertz sound is easily audible even to aging ears at about 3 kilohertz. Leslie also used a more sophisticated device called an Echometer Touch.
Although big brown bats weigh only about 18 grams, they nonetheless have wingspans of about 13 inches and are an impressive sight as they flit overhead. We learned that they tend to fly over groups of people because we exhale CO2, which attracts insects. Thanks to the Baton, we were alerted to the pulses of sound they produce as they exit the barn and hunt for prey. When Leslie tallied the counts from each group of observers, the final count was a little over fifty, twenty more than had been observed in the spring.
These bats are impressive insectivores, capable of consuming up to 1000 insects per hour. Aided by the listening devices, we got to witness them diving to capture flying insects. The big brown bat has been largely spared white nose syndrome, and is one of the most abundant bat species in North America. They have complex social lives, with relationships based on factors other than kinship. They can apparently interact with bats from adjoining colonies as well.
Leslie maintains a website, virginiabats.org, which goes into detail about the desirability of increasing bat populations and strategies to achieve this, with good summaries of their various programs. She is a remarkable living resource, having devoted herself to this cause for the past twenty-one years. She is hoping to have further similar events in the coming months. I’m looking forward to further participation.
– Zack Perdue, Cohort VII, July 2022