The Threats of White-Nose Syndrome on the Tennessee River Gorge Bat Communities
By Quentin Miller
Credit: Amber Hart
The Tennessee River Gorge is home to a rich cave system that formed over 300 million years ago when water seeped into the cracks of the Earth and dissolved limestone rock, forming underground pipelines for gravity and water to play its part. These caves are incredibly fragile, providing a unique ecosystem for a variety of species such as the Tennessee cave salamander, Barr’s cave spider, southern crayfish etc.
Meet the Tricolored Bat
One species that is of high interest here at TRGT is the Tricolored bat. These furry natives are one of the smallest bat species in North America, coming in at the same weight as a quarter! The name comes from their fur’s physical attributes in that each specific hair has three components: a dark base, a lighter middle, and a yellow/brown tip. Tricolored bats seek “hibernaculums” or hibernation dwellings during the winter season. One such hibernaculum is Hugden Cave. Hugden Cave has been under the protection of TRGT since 1987 and is home to a colony of Tricolored bats. In 2018, the Tennessee Wildlife Resource Agency (TWRA) recorded 48 Tricolored bats hibernating in Hugden Cave with some displaying diagnostic symptoms of White Nose Syndrome. As of September 2022, a proposal was submitted for this species to be listed as an endangered species in large part due to the deleterious effects of White-Nose Syndrome.
What is White-Nose Syndrome?
Credit: Pete Pattavina
White-Nose syndrome is a complex fungus (Pseudogymnoascus destructans) disease that affects hibernating bat species. The fungus thrives in cold, dark, damp places making caves an ideal habitat. Susceptible bats (tri-colored bat, Indiana bat, gray bat etc.) can be invaded by this fungus during hibernation as the fungus will make home on areas of bare skin such as their nose. The fungus can cause skin infections and wing degradation but more importantly, it disturbs and awakens the bat during hibernation, depleting vital fat reserves necessary for winter survival.
The disease was first identified back in 2006 in New York. It has gone on to spread across North America (39 states) and many Canadian Provinces, killing millions of bats and in some areas depleting the native population by 90-100%. The disease is well established in east and midwest U.S. states but has gone on to spread to the mountain west with some confirmation in California and Washington. Scientists continue to study this fungus around the clock as its introduction has ignited one of the deadliest outbreaks in wild mammals in recent history. Molecular evidence suggests that P. destructans evolved from coexisting with Europe/Asia bat communities to becoming a specialist pathogen that seeks out living bat tissue to grow and replicate.
Early Signs of Resistance?
While the news may seem bleak, there is growing evidence of a resistance from this disease in bats affected early in the outbreak. Scientists have studied colonies of little brown bats located in New England and found that survivors of White Nose Syndrome exhibit unique gene sequencing not found in bats that were killed by the fungus disease. The unique genomic trait supports weight gain before hibernation and behavior during hibernation, suggesting that the influx of White Nose Syndrome within these populations has led to a rapid evolution.
Quentin entering a room in Hugden Cave!
This year, the TRGT field team and the TWRA monitoring team conducted another bat survey count at Hugden Cave. 95 tricolored bats were observed, doubling the population size from 2018! The monitoring team did observe diagnostic evidence of White Nose Syndrome among a few bats within the cave. Even though our population has doubled over the course of five years, monitoring must remain a high priority at TRGT, and mitigation measures must be acted on.
What can I do about White Nose Syndrome?
From the avid cave adventurers to the urban explorers, there are many things that can be done to help mitigate the spread of White Nose Syndrome.
Awareness
Keeping citizens informed and acknowledging the threats of White Nose Syndrome is paramount. Bats play a vital role in pest control, plant pollination, and seed dispersal across the world. A study recently estimated that bats consume enough pests including those pesky mosquitoes to save more than 1 billion dollars a year in overall crop damage and pesticide control. While few people want a bat flying over their head late at night, they are still very misunderstood and deserve a great appreciation and attention,
Clean Caving and Permits
For the more adventurous, caves can be safely and responsibly explored by adhering to strict protocol before and after entering a cave. Here in Chattanooga, we have the pleasure of accessing cave information and permits from the Southeastern Cave Conservancy (SCC). SCC provides access for caving permits
Reporting
Injured or dead bats should be reported to agencies like the Tennessee Wildlife Resource Agency. Reporting helps experts identify areas that may be seeing declines in population and warrant further investigation.
To learn more about Tennessee’s unique caves and the impacts of White Nose Syndrome, please visit the Southastern Cave Conservancy.