Scientists Discover Cause of Bat Deaths


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
1 Jan

This sounds similar to the world wide phenomenon of frogs being killed off by fungal infections as well – and I love frogs, several species have already been wiped out. That is very disturbing to hear about what is going on in the US.

In Australia we have have had a bit of hysteria because they found that bat droppings have been getting into the drinking water and food of horses kept in fields, then when they ingest the bat droppings they can develop the Hendra Virus which is deadly to horses as well as humans (spread by contact with infected mucous). We have had many horse deaths and a few human deaths in Australia in the past couple of years, which is why they had to trace the source, and a lot of hysteria in communities where there are bats with people wanting to destroy the colony or move them on. But they are all an important part of the food chain and protected thank goodness. One town was given permission to move them on though, so I wonder what their insect population will be like this year!! I guess I can understand how they feel because 3 out of 4 people who contract the virus have died.

For your bats Will, I wonder how helpful it would be to make sure that they have a water source – or even sweetened water – they might not like that if they are insect eaters but maybe just having water available will help.


2 Robin Henderson

In my home county we had flocks of little brown bats when I was kid. Recently I went back, and noticed that they’d all been replaced by fewer, much larger bats. (Large browns, is my guess.) I don’t know why this is; perhaps the bigger guys are more resistant to the fungus, or to humans, or both.

Fortunately here on the coast we still have a healthy population of little browns. Too healthy for my taste; they keep getting into the house, and I can’t figure out how.

Either way, I hope this fungus thing resolves itselt. Bats rock.


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3 Binky

I hope they can develop some sort of specific fungicide to treat the fungus. But why are bats only now becoming infected? Are they somehow now weaker or more stressed? Or has the fungus found some new breeding ground? It’s very strange how these things can seemingly come out of nowhere and be a major threat within such a short time. Bats, bees… and the Tasmania Devil may also be wiped out by a new cancer that is spread through saliva.
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4 Anna

Will everywhere we turn around there is something going on with nature. I just recently read an article about acid rain killing sugar maples, because it depletes calcium from soil. However, it also slows down the degradation of the leaves thus preventing the new seedlings from growing. The good thing that we know what it is. Not having a cure yet, scares me.

On the side note when growing up we always thought bats were bad, and here you are building bats houses.

I wish I knew the answer, spraying pesticides would be the last thing on my mind. Spraying chemicals is never localized, unless they are treated one bat at a time, probably nearly impossible.

Anna 🙂


5 Tony McGurk

Very interesting article Will. My 1st thought was that the wings being affected would prevent flight & getting food too. Regardless of the species all these sorts of diseases have to have a long term effect on our planets ecological balance.

Binky mentioned Bees. I saw a documentary on one of the Antarctic Bases once & they had huge hydroponic sheds. Their botanist showed that they had to go around with a brush on all the plant’s flowers to pollinate because of no bees & other insects there. Something I wouldn’t have even thought of.


6 Felicia

That is indeed a very sad dilemma for the brown bats you featured. I think it has a similarity with the fungus that infects maize crops in tropical countries, I remember it’s called corn smut, and even if many farmers destroy these smut-infected crops, some people in Mexico still opt to eat it as a delicacy!


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