Q&A: Bats in Pennsylvania
Fifteen years ago, a fungal disease swept through Pennsylvania, devastating the state's hibernating bat population. We recently had a chance to sit down with Mollie Byrne, a Wildlife Disease Biology Technician with the Pennsylvania Game Commission who travels across the Commonwealth inspecting bat hibernacula and individuals for health and disease, to chat about what's changed since then.
Could you summarize the current state of bats in Pennsylvania?
We lost 98-99% of our Little brown bat population to White Nose Syndrome (WNS) after the fungal disease swept through the state 15 years ago. In the past few years, we have finally started to see numbers plateauing and even increasing in some hibernacula. This increase may not represent just population growth however, as the large and quickly increasing numbers may be indicative of survivors grouping together in the best hibernacula sites. Even with these increasing numbers, our bats are not out of the woods, as their numbers are still decreasing throughout their entire range.
How many species of bats are found in Pennsylvania and are any thriving? What threats to bat populations exist?
We have 9 species of bat in the state of Pennsylvania. Three of them are migratory species that roost in trees and fly south for the winter: Hoary bat (Lasiurus cinereus), Eastern red bat (Lasiurus borealis), and Silver-haired bat (Lasiurus noctivagans).
The remaining six species are hibernating bats: Big brown bat (Eptesicus fuscus), Little brown bat (Myotis Lucifugus), Tricolor bat (Perimyotis subflavus), Eastern small-footed bat (Myotis leibii), Indiana bat (Myotis sodalis), and Northern long-eared bat (Myotis septentrionalis).
Some species are doing much better than others, but I personally wouldn’t say any species is thriving due to the threats posed by WNS, windmills, outdoor cats, pesticides, and humans.
Are certain species showing immunity to White Nose Syndrome?
Technically speaking, a portion of the hibernating bats that survived WNS likely had some kind of an evolutionary advantage that allowed them to survive, regardless of species. The process of evolution occurs when these survivors successfully reproduce and pass those unique genetic traits onto their offspring through many generations. Overall, all hibernating bat species were heavily affected by WNS, but Big brown bats are the species that seem to have been affected the least.
What can landowners do to support bats?
There’s A LOT that landowners can do to support bats! One of the best ways to help is to properly hang quality bat boxes on your property. Quality bat boxes, box construction plans, and instructions on how and where to place them can be found online through a multitude of different companies, such as Bat BnB, Bat Conservation and Management, and the Pennsylvania Game Commission’s website.
Another way to support bats is to keep pet cats indoors, as they commonly prey upon bats when given the opportunity to do so.
One last way for landowners to support bats is by reducing or completely eliminating the use of pesticides and herbicides on their properties, as well as by planting native plants. Insects are the only food source that Pennsylvania bats have, and many insects, such as moths, rely on native plant species for survival and to complete their lifecycles. Without bugs such as mosquitos, moths, and flying beetles, bats would not exist in the state.
What’s your favorite bat species and why?
My favorite PA bat species is the Hoary bat, hands down. They have such unique coloration when compared to the other bats, and they are also the largest bat in North America. They weigh between 25-45 grams and can have a 16-inch wingspan. For reference, the average Little brown bat weighs 7-10 grams and has a wingspan between 9-11 inches. I even have a (roughly) life-size greyscale Hoary bat tattooed on my side/rib cage!
Overall, I think my favorite bat species of all time is the Pied-butterfly bat, which is found in Africa. Just look it up, you will not be disappointed.
Could you describe your most memorable bat encounter?
It was extremely hard to pinpoint just one memorable bat encounter to talk about here, but there is one I have in particular that is both memorable and extremely gratifying. The Pennsylvania Game Commission does some spraying of a fungicide in a few hiber sites to combat WNS. In Spring 2022, we found a federally endangered Northern long-eared bat in one of these sites, and it had no WNS on it! This was confirmed through UV, as WNS glows orange when exposed to UV light. The hard work, intense hours, and buckets of sweat produced by spraying the site year after year were well worth it when we found that little guy.
Lead photo: Little brown bat courtesy of Mollie Byrne