I hate to get all serious, but this is a topic near-and-dear to me, and one that needs more publicity. And while Zooillogix readers are intelligent and well-informed (and smoking hot, I might add), I want to be sure everyone is aware of the progress and potential of this epidemic. Plus, I know I’m not the only batfan here.
In February of 2006, a caver in eastern New York photographed a group of hibernating bats with an unusual white substance on their muzzles. The following winter, bats were noted flying outside of caves months before they typically come out of hibernation. Then there were the reports of unprecedented numbers of sick, dying, and dead bats in and around caves, and investigations confirming mortality rates of over 90% in these hibernacula.
“White-nose syndrome” was born.
As scenes like those below became all too common, scientists began to tackle the mysteries behind this previously unknown phenomenon.
Bats with white-nose syndrome (WNS) are characterized by the presence of a white fungus on their muzzles, ears, and wings. They appear to lose body fat during the winter, perhaps causing them to leave their hibernacula in search of food months before spring brings the insects they require to survive. The result is starvation. Mass starvation, in many cases. Elizabeth Kolbert described the scene in the Aeolus Cave in Vermont,
“The ground is littered with bat bones. There are so many of them- thousands upon thousands – that you can’t take a step without crunching them underfoot.” *
Kolbert joined members of the Vermont Fish and Wildlife Department during a bat census of the cave. The result? In a cave normally housing over three thousand bats of at least 4 species, the census total came to 112.
Since its discovery four years ago, WNS has continued to spread across the continent. Just last month, both Maryland and Ontario reported their first confirmed cases of WNS. The disease is believed to be spread from one cave to another both by infected bats and by cavers who may carry the fungus on their clothing or gear. In an attempt to prevent the spread of WNS, many private land owners with caves on their properties have put up signs or even barriers to prevent people from going inside. While this may help stem the spread, additional solutions are going to be necessary.
Although much is still unknown about WNS, scientists at the National Wildlife Health Center have identified the white substance as a previously unknown member of the fungal group Geomyces. This genus represents fungi commonly found in soil and known for their unusual ability to grow and reproduce at temperatures around 40°F. The species involved in WNS, G. destructans, invades the skin and wing of the bat. Sweat glands and hair follicles of infected bats are filled with hyphae, the long branching cell of a fungus in its growth state.
Whether or not the fungal infection is the cause of WNS or simply an opportunistic pathogen remains unclear. Additionally, it is unknown whether G. destructans is a recently introduced species to North America or if it existed prior to the observed devastation of bat colonies. The same fungus has been identified on bats in Europe, but without the emaciation and mortality observed in the U.S. This may mean the fungus originated in Europe, where local bat species developed immunity to the pathogen, or the fungal strain observed in the U.S. is a mutated form of that seen in Europe.
Interestingly, similarities have been noted between the disease process caused by G. destructans and the chytrid fungus, Batrachochytrium dendrobatidis, currently causing a significant worldwide decline in amphibian populations. Others have noted a similar disease course as observed in colony collapse disorder, a phenomenon of yet-to-be-determined origin resulting in a drastic disappearance of honey bee colonies in North America.
Like chytridiomycosis in amphibians and colony collapse disorder in honey bees, white-nose syndrome does not get the attention it deserves in part because it does not cause disease in humans. Adding insult to injury, the all-too-common perception of bats as disease-ridden, flying rats to be feared and avoided does not award them sufficient sympathy. But I remind those people that these amazing little critters can consume 1,000 insects per hour! The U.S. Forest Service estimates that we are already seeing an extra 2.4 million pounds of bugs each year in the absence of the bats that have succumbed to WNS. This means an extra 2.4 million pounds of crop pests and mosquitoes, a number that will continue to grow as more bats die every year. Combined with the growing distribution of insects that serve as vectors for diseases like malaria, dengue fever, and West Nile virus, we could be looking at a very different world in a very short time.
So before things go all armageddon, let’s spread the word that we need our little Chiroptera friends.
* The New Yorker, March 29, 2010, pg. 42