White-Nose Syndrome

Little Brown Bats exhibiting WNS symptoms

photo courtesy of Nancy Heaslip, New York Department of Environmental Conservation

I'm going to switch gears now and tell you about something quite serious that is devastating bat populations in the Northeastern United States and continuing to spread. It is called White-Nose Syndrome, or WNS, and since its discovery in a cave near Albany, New York in February 2006, it has wiped out an estimated 1 million bats in 9 states - with some caves experiencing a 90-100% mortality rate! - and scientists have yet to figure out the how's and the why's.

So far, it has affected 6 different bat species, all of which are insectivorous and hibernating species - the endangered Indiana myotis (Myotis sodalis), the little brown myotis (Myotis lucifugus), the big brown bat (Eptesicus fuscus), the tri-colored bat (Perimyotis subflavus), the northern myotis (Myotis septentrionalis), and the eastern small-footed myotis (Myotis leibii).

To begin, let me provide a bit of background information concerning hibernation (because this appears to be when the bats are dying). During this state, the bats' body temperature and heart rate slow down dramatically (sometimes within 1 degree of the temperature of the cave!) and they live off of their previously stored body fat. If a bat is disturbed too many times during hibernation, it is likely to die because all of the fat reserves are used up, and the bat cannot go out in search of more food because it is the dead of winter, and there are no insects to be found.

Again, it is at some point in their hibernation that these bats are dying. The dead bats are found inside their hibernation caves or just outside of them. They are emaciated and have a never-before-seen white fungus on their noses, ears, and/or wings. However, it is not yet clear whether it is the fungus, named Geomyces destructans, that is killing the bats - there is no evidence that a fungus has ever killed a mammal - or if the fungus is an opportunistic invader, coming in after the bats have been weakened by something else. What can be said of the fungus is that it thrives in the same temperature range and dark, moist conditions in which the bats hibernate. It is not known how the fungus - which is genetically similar in all of the cave sites - was introduced. It is known, however, that the fungus is transmitted from place to place via fungal spores, which could be carried on the bat's fur, the clothes or shoes of humans, or through the air.

Now, I mentioned that the dead bats found are emaciated. What appears to be happening is that the bats are losing their body fat mid-winter, so that they either die before they are able to wake from their torpor, or they wake prematurely and fly outside in search for food and freeze. (The few bats that do survive the winter are found to have wing damage from frostbite and/or the fungus.)

Some scientists have hypothesized that the loss of body fat is due to an inadequate supply of polyunsaturated fats that are supplied by certain insects, which are dying off because of pesticides. (Pesticides that shouldn't need to be used in the first place because these bats act as nature's pest controllers by consuming these insects.) It has also been suggested that the bats perhaps rouse prematurely because of irritation due to the fungus, which reaches their dermis, or living part of the skin. The fungus could also have physiological effects on the delicate wing membrane which regulates body temperature and blood pressure, thus interrupting hibernation. The warm or variable winter weather is also a hypothesis as to why the bats are waking mid-winter.

Unfortunately, the money needed to fund WNS research is slow-coming. So far it has come mainly from Bat Conservation International, the National Speleological Society and other non-governmental sources. The scientific community is trying to obtain more funding from the federal government, but according to BCI's website, the Senate Appropriations Committee report "contains only $500,000 of the $11 million identified by the scientific community for immediate WNS funding."

Such a devastating loss in bat populations doesn't just mean that 1 million bats are dead. The loss of 1 million bats means that the organisms supported by the guano on the cave floor will die, the pest population that the bats are no longer consuming will increase, you will get more mosquito bites, the increased number of agricultural pests will damage more crops, the crops will be sprayed with more pesticide... And - if the pesticide/polyunsaturated fat hypothesis holds true - more bats will die. Of course, the greatest thing at stake here is the potential extinction of entire bat species.

Bat Killer: White-Nose Syndrome [video] (Scientific American)
Night Stalker: White-Nose Fungus in Bats--Why It's Our Problem, Too (Scientific American)
interview with Dr. Thomas Kunz, Professor of Biology at Boston University, about WNS (Earthfiles)
BCI's WNS page & how you can help

related articles that may be of interest:
Colony Collapse Disorder (Wikipedia)
Is the Frog-Killing Chytrid Fungus Fueled by Climate Fluctuations (Scientific American)