Scientists Discover Cause of Bat Deaths

by updated 2011/12/23

White Nose Syndrome on Bat

A Little Brown Bat With White Nose Syndrome

A couple of years ago I wrote about a mysterious bat-killing disease called “White Nose Syndrome”.  Just recently, researchers claim they have discovered the specific cause and pathology of the disease.  White Nose Syndrome is caused by a previously unknown fungus, Geomyces destructans.  Destructans.  Appropriate name, I think.  This is good news in that a specific pathogen has been discovered, but a solution to the problem is still desperately needed if bat populations are to be saved.

Even though the fungus is named after the distinctive growth pattern on the bat’s noses, the actual damage the fungus causes seems to be unrelated to this most distinctive location of the fungus.  Researchers believe that the severe damage the fungus causes to the wings of bats is what leads to their death.  You would think that the wing damage would cause the bats to be unable to fly, leading to starvation, but the real damage is completely unrelated to what we think of when talking about bat wings.

Wingspan of a Little Brown Bat

Yes, the wings are something like 75% or the skin area on a bat and this wing ratio is one reason bats are such amazing flyers.  But, the bats are dying when they are hibernating, not when out trying to hunt for insects so what is up with that?  When bats are hibernating they do not eat or drink.  To avoid dehydration, their skin must prevent water loss to the atmosphere of the cave.  Turns out that because bat wings are the main component of a bat’s skin, the wing, (skin), has a crucial role in preventing the loss of water while that bat is hibernating all winter long.  With wings damaged by the fungus, researches think the bats are getting dehydrated and are unable to make it through their long hibernation.

There are also other important physiological functions bat wings perform that are thought to be damaged by the fungus.  One example is passing gas through the wings.  Not passing gas in the way that sounds, but I mean exchanging carbon dioxide and waste products for oxygen in a way similar to our lung function.  Bat heart rates go from as much as 1,000 beats per minute down to 20 or 30 beats during hibernation, and breathing slows to 2 or 3 breaths per minute.  Most respiratory function occurs through bat wings when they are hibernating and damaged wings mean damaged respiration.

Close up of bat faceWing complications resulting from the fungus might not directly kill a bat but may wake it from hibernation because of the damage or irritation the fungus causes.  For example, if Northeast United States bats wake up in the middle of winter and fly out of the cave looking for insects; that is a recipe for disaster.  Even if a bat does not wake up to the point of flying out into the winter, just rousing a few times during hibernation can cause increased burning of body fat and lead to starvation before the winter, and their hibernation, is over.

Unfortunately, even looking through the latest articles on White Nose Syndrome, I could not find any real ideas about how to fix this problem.  If any of you come across anything that talks about a cure please let me know as I would be very interested in reading about it.  I thought about fixes like spraying fungicides in the caves where bats hibernate but it turns out that has real problems as a potential solution.  One problem is that caves are amazingly delicate ecosystems that may be damaged by such spraying.  Also there are some beneficial fungi that could also be killed by spraying.  If these beneficial fungi are killed and the Geomyces destructans fungus proves resistent, the problem could be made much worse.

Step one, identification of the cause of White Nose Syndrome, has been accomplished.  Now the work begins to see if these declining bat populations can be saved.  Bats play a crucial role in pest control, pollination, and agriculture.  I have built bat houses to try and encourage bats to stay around our home, but have not had success enticing them to sleep over.  I am thinking I will try one of these commercially available Bat Houses and see if that works.

Protecting bats is critically important but there may also be important lessons to be learned from this disease.  I have not seen the movie “Contagion” yet, but from what I have read the movie has a very plausible plot and the similarities between what is happening to the bats and what could happen to us humans is worrying.

Will Sig

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