Growing up in the Shenandoah Valley with a dad who is a bat biologist, my sisters and I would spend weekends scrambling through caves, feeding injured bats water droplets through straws, and avoiding the Ziplock bags of frozen bat specimens when reaching into the garage freezer for a frozen pizza. A few times a year my dad would travel to the Eastern Shore of Virginia to study coastal bats on the barrier islands with his colleagues. Bats at the beach? That notion always confounded me. Most people equate bats with deep, echoing caves in the mountains, not flat marshy islands. Yet bats are important members of our coastal ecosystems.
Bats are divided into two main groups- tree bats and cave bats. The Eastern Shore is home to bat species that prefer tree dwellings. The six most common species that inhabit Marylandโs Atlantic coast include Eastern Red Bats, Evening Bats, Big Brown Bats, Hoary Bats, Tri-Colored Bats, and Silver-Haired Bats. You have probably noticed these nocturnal insectivores emerging in the purple dusk of summer evenings, flitting over the marsh or around forest edges chasing mosquitos, flies, moths, and other small insects. The US Department of Agriculture estimates that a small bat can catch 1,000 or more insects in a single hour. If a bat worked for a pest control service, they would earn employee of the month throughout the entire summer season. It is estimated that bats provide about $22.9 billion in pest control for the agricultural industry across the U.S. (Boyles et al. 2011). These positive benefits that wildlife or ecosystems provide to people are called ecosystem services. Bats make up about one-fifth of all mammals on Earth, and the ecosystem services they provide make them an invaluable part of our natural world, even here on the Coastal Bays.
Bats on the Shore are not only valued for what they can do for us humans, like reduce the number of mosquito bites we itch each summer. They are genuinely fascinating creatures, and each species has its own unique characteristics. Eastern Red Bats, which are the most common tree bats in Maryland, can fly up to 40 miles per hour. On the contrary, Silver-Haired Bats live life in the slow lane and fly at unhurried, leisurely speeds. The Hoary bat is the largest bat in Maryland, with a wingspan that can reach 16 inches. Evening Bats win the undesirable award of smelliest bat. They have a strong, pungent odor that earns them this prize.
Bats use echolocation to find food and navigate at night by emitting sound waves through their mouth or nose at frequencies above human hearing and listening for the echoes to bounce back. From the echoes they can create a detailed map of the objects in their environment, including the size, shape, and texture of their surroundings. Scientists are learning from batsโ use of echolocation to develop navigational aids for the blind.
When the tourists have packed up and driven back across the bridge for the season, and the ocean spits a chilly spray into the crisp air, winterโs arrival is imminent, and bats have a few options for how to prepare. They may hibernate, migrate, enter torpor, or choose to do a combination of these. Most species that roost in trees migrate south to warmer areas with active insect populations for a steady food source. They may enter bouts of torpor, in which their heart rate decreases significantly, their body temperature drops to near freezing, and all other bodily functions slow to a crawl to conserve energy. This state of torpor can reduce energy usage by 98%. Torpor can last for only a few hours, or a few months, in which this extended state of torpor becomes a hibernation. For example, many Eastern Red Bats migrate south for the winter, but some choose to stay in Maryland and make themselves at home in hollow trees or leaf litter to enter torpor. During warm winter days they may awaken and resume activity, and during this time you may notice them flying about as if it were a balmy summer night.
Bats in much of the U.S. are in serious decline. Habitat loss and disease are the main culprits causing all 10 of the bat species occurring in Maryland to be listed as โSpecies of Greatest Conservation Needโ. In 2006 a fungal disease called white-nose syndrome was introduced from abroad into an east coast cave. It was first discovered in upstate New York and has been spreading with a vengeance throughout much of the U.S. and into Canada. White-nose syndrome (WNS) is the worst wildlife disease outbreak in North American history. It mainly affects cave-dwelling species of bats but can also impact tree species. In caves affected by WNS, biologists have observed as much as 100% decline in hibernating bats. It has decimated entire species of bats as well- the populations of Northern Long-Eared, Little Brown, and Tri-Colored bats have been reduced by over 90% in less than 10 years. White-nose syndrome is an invasive fungus that acts as a silent killer, affecting hibernating bats by growing into their skin and causing disruptions to their fragile state of hibernation. These interruptions lead to dehydration, starvation, and death. The stalactite-decorated ceilings of the caves I visited as a child in the days before white-nose syndrome were carpeted with the soft fur of thousands of bats. Today those caves echo with a cold, haunting silence.
At this point we all may find ourselves asking, โIs there hope?โ. Some species of bats are more resilient to disease than others. While there is no cure for white-nose syndrome, scientists around the world have been working tirelessly to find answers and solutions to offer a brighter future for bats across North America. Many caves have been closed to recreational cavers to prevent the spread of disease that may be transported from human clothing and gear. The awareness of the fragility of many bat populations and the important role they play in ecosystems from the mountains to the coast enables us to fight for these important species. As long as bats continue to dance across the dusky treeline on humid evenings to the cacophony of cicadas and spring peepers, there will be hope.
