Has WNS slowed down?

[PYoungbaer]

Although not all this winter's survey data is in, it appears to me that the spread of WNS has slowed significantly.

Yes, we added two new states to the WNS map, Indiana and North Carolina, but the number of affected bats seems low. Simply early arrival, or is it the outer fringes? At the same time, Kentucky remains WNS-free as of last report, and Missouri, which had a couple suspect bats, has no reports this year, either.

On the other hand, previously affected states continued with their casualties. Pennsylvania and Virginia seem to be the most affected this year, with additional spread in West Virginia.

Here's what Tennessee's Dave Pelren had to say in an article after a survey found no new evidence of WNS in a suspect site:

"The signs of the disease have not been as severe this year as most of us expected."

http://www.knoxnews.com/news/2011/mar/29/cave-bats-get-checkups/

Could it be that those who speculated about a southern reach due to Mean Average Surface Temperature being near the high range of optimal fungal growth were correct? While certain cave and mine microclimates are colder, in general there could be a line of demarcation, as a number of people suggested years ago. Others also suggested exactly what the article says, that with the shorter winters, even if the bats contract the fungus, food is available before starvation occurs.

Although the media continues to repeat that "over a million" bats have died - a number unchanged for nearly two years, I'm not aware of anyone keeping a centralized count. That number made sense to me when it first came out, based on my knowledge of prior bat populations in the Northeast. However, except for New York and Vermont I've not seen any decent longitudinal statewide data, although there are numbers from specific sites (Hellhole Cave, West Virginia; Chester Mines, Massachusetts as examples). One Vermont article this week quotes Scott Darling as saying it's nearly two million, but that's the first I've seen anyone mention that number, and I've seen no data to confirm it.

I would be very interested to receive any information that would confirm or deny either the numbers of bat mortalities, or that the spread of WNS has slowed. Thank you.

[dfcaver]

This could be a dangerous question - there are some that would point to the closing of caves as responsible for the slowing of WNS. Of course, that involves selective memory from last year, when closing caves did nothing to slow the spread.

An imperfect method is simply counting the newly infected counties for each season. Up until this year, the number of WNS positive counties almost doubled each year. Now this winter, a major slowdown in it's advance.

A couple of things in play, however. One, WNS is running out of new counties in the Northeast. Some states simply don't have many "new" counties left to be infected. Two, cutting of budgets of state employees to go out and look for WNS. Three, lack of reporting - Pennsylvania announced "4000" WNS sites earlier this winter, but has added just three counties to the map. And perhaps four - that there is a geographic limit to the spread. Five - with fewer cavers out there caving, sites will be missed. Six - WNS was already endemic in the Northeast before we looked for it, and it's spread will turn out to be somewhat slower than first thought. We may have been playing catch up from the first.

In Central Pennsylvania, the mass deaths continue to occur, with our caves losing 65 to 98% of the pre epidemic populations. We are still seeing caves that appear to be in the early stages of infection, with the majority of the bats currently infected. Some of these will survive long enough to mingle this spring, I'm sure.

[rlboyce]

http://www.dnr.state.md.us/dnrnews/pressrelease2011/032911a.asp

+1 for Washington County, MD (the county with largest density of caves), and possibly more on the way as we wait on results.

[dfcaver]

Number of Counties newly infected, and total infected counties.

2006-07 - 2 - Total 2
2007-08 - 12 - 14
2008-09 - 27 - 41
2009-10 - 45 - 96
2010-11 - 14 - 110

Statistically, we certainly could have expected about 90 newly positive counties to show up. Of course, we started the winter with 96 counties that could not be newly infected. Also, we've got an awfully small sample size. Personally, I remain very curious about KY.

There's a real elevation correlation as well. The Catskills, the Adirondacks, Berkshires, Litchfield Hills, Green and White Mountains, the Alleghenies and Appalachian Ridges, into the Shenandoah and Smokie Mountains. Of course, that's where the caves and mines are, and hence the bats. But it would be cooler in the mountains, as well.

[wyandottecaver]

The problem with statistics is: they lie.

I'll address the counties issue first, then Peter's question.

Counties
The problem with using a # of counties approach is:
1) There is no linkage between how many counties exist with X miles of a previous site. Thus within 200 miles of 2006 sites there might be 100 counties, but within 100 miles of 2009 sites there might be 50.
2) There is no linkage between how many potential counties and how many actually have significant bat populations. Since bats are the primary (maybe only) vector, then your chance of occurance rises with bat population. In Indiana, we only have 3 counties so far but those probably house 25-40% of the states bats. Add about 5 counties to those and your probably looking at 90%. So 3 counties gets maybe 40% and about 8 counties out of 91 total in indiana gets you 90% of our cave bats.

Peter
If you look at the WNS map you see that 07-08 was the backfilling the local area around 06. 08-09 was more backfilling and a rapid expansion down the migratory path along the appalachians. 09-10 was more backfilling and rapid expansion along the migration paths in the midwest and canada. so now we are at 10-11.

What's different? We waited longer and the WNS frontier is generally in warmer climates. Did we miss some sites due to hungry WNS bats bolting early? maybe. We also are pretty sure that WNS bats are simply dispersing farther in the midwest as opposed to the NE. That means our ability to actually identify sites is lower. Finally, as has been said, the willingness of cavers to report WNS has dropped.

It might be WNS slowed in 10-11....but it might just be that once past the appalachians, the search area increased dramatically and the "WNS Cruise Missiles" (sick bats) had a bigger area to disperse in.

Finally, as to numbers. I do think leength and severity of winter will make a big difference. Otherwise its following much the same pattern I think. The backfill areas of 09-10 are being hit hard while the "new" 10-11 sites are in the initial stages. The hibernacula showing the most obvious signs in Indiana wasn't even entered. (there should be thermal data, but I haven't heard about that yet) We could have lost 300 bats or 30,000 at one site. As a side note, based on some unofficial correspondence, I think we will find that next year most of the bat rich areas of IN will be heavily infected.

[PYoungbaer]

Thanks for the replies. I completely agree that counting counties doesn't really tell us anything, but given the desire to protect locations (sometimes by law, sometimes by landowner requirement), it really doesn't give a clear picture of impact.

I don't disagree at all with the observations about back-filling already affected areas, about the concentration of caves and mines (and thus, bats), nor about the possible/probable southern limitations.

I disagree with "WNS was already endemic in the Northeast before we looked for it, and it's spread will turn out to be somewhat slower than first thought. We may have been playing catch up from the first." I can personally vouch for an abnormally high level of surveying in the early years to find where it was and where it wasn't. I can tell you that I and many others here probably spent more time in northeastern caves in the winter and early spring than we ever had (it's neither easy nor pleasant to do many of these at that time of year, and we generally don't anyway so as not to disturb the bats). We were so thorough as to discover previously unknown hibernacula.

It would be very helpful to be looking at real bat population numbers from many more states.

Keep your comments coming. Thanks.

[graveleye]

Could it be that those who speculated about a southern reach due to Mean Average Surface Temperature being near the high range of optimal fungal growth were correct? While certain cave and mine microclimates are colder, in general there could be a line of demarcation, as a number of people suggested years ago.

I held this theory at first as just a means of hope, but now two years later, I'm starting to believe that the disease just might not make it too far south... I'll keep hanging on to the hope.

[BrianC]

Much stated is possibly true, But the reason I'm skeptical is the state of Kentucky. Ky. is in the temperate range, and on the migratory path. Why not much speculation of this? I have stated in the past that the cause of the fungal aggressiveness and reason for WNS could be that good bacterial growth on skin has been compromised allowing the fungus to grow where as healthy bacteria will keep it in check. Bacterial growth can be compromised by both insecticide and pesticide agents Bacterial strains will mutate to maintain themselves. Areas that have been ravaged already might just not be able to get ahead, where areas that have had some fungal spread could have been able to defend against the outbreak by mutation.

[nathanroser]

There's also the question that some bat species may be more resilient to infection and starvation than others. In the event that the bat species that have been hit the hardest never do recover, hopefully any resistant species can move in to fill the gap so there are still good bat populations to control insects and pollinate plants, and to just be awesome because they're so fascinating and adorable.

[BrianC]

to just be awesome because they're so fascinating and adorable.

I see all nature as awesome. I don't see bats having any impact on pest control or pollination where wns has the potential of showing up. I know that some use this as a tactic for throwing money at wns, but looking at the use in the northeast where the mortality has been the worst, no additional pesticide increase has been noted.

[nathanroser]

Well the pesticide use thing probably has to do with the fact that the rocky and rough terrain of major cave and mine areas doesn't make good farmland. But one thing that does come to mind about WNS possibly being a result of the loss of beneficial bacteria on bats is that if the root cause is such, how the heck would it be spreading unless there is some other pathogen preying on bacteria that leads to the good bacteria loss and then the fungal growth.

[self-deleted_user]

In KY where I was ridgewalking (and there are caves) though, it is farmland...lots of cattle not crops though. They're always throwing stuff into holes to keep the cows from falling in! So the mountainous rocky terrain isn't necessarily needed for caves - just limestone exposed. Or like Mendip or the Dales out in England, here is a view out of the Dump (in the Yorkshire Dales, best vert caving in England) - prolly can't tell but those are sheep all over the place :) It doesn't exactly appear all rocky and mountainous....
The Dales - Views from The Dump 03 by Sunguramy, on Flickr

[BrianC]

Well the pesticide use thing probably has to do with the fact that the rocky and rough terrain of major cave and mine areas doesn't make good farmland. But one thing that does come to mind about WNS possibly being a result of the loss of beneficial bacteria on bats is that if the root cause is such, how the heck would it be spreading unless there is some other pathogen preying on bacteria that leads to the good bacteria loss and then the fungal growth.

Exactly the issue and this possible answer, The bats themselves can only spread that kind of pathogen, therefore providing evidence of why the very spread moving along migratory habits. Of course, some bats will fly(hitch a ride) to areas outside the normal migratory routs for many reasons, providing evidence for wns being seen in other caves and mines.

[tncaver]

WNS was discovered in an Ohio mine this year. The mine was gated to keep people out yet the bats are infected anyway. How long does it take for
the geniuses in the USFWS to realize that bats are spreading WNS and bat friendly gates won't keep it out. However, gates do offer another way for our government to spend more taxpayer money. Since the Federal Government is already broke (owing billions to China and who knows who else), they should stop
wasting money on gating mines and caves and spend it on research to cure WNS (sorry to the people who build gates for a living).

http://www.fws.gov/WhiteNoseSyndrome/pd ... elease.pdf

[nathanroser]

In KY where I was ridgewalking (and there are caves) though, it is farmland...lots of cattle not crops though. They're always throwing stuff into holes to keep the cows from falling in! So the mountainous rocky terrain isn't necessarily needed for caves - just limestone exposed. Or like Mendip or the Dales out in England, here is a view out of the Dump (in the Yorkshire Dales, best vert caving in England) - prolly can't tell but those are sheep all over the place :) It doesn't exactly appear all rocky and mountainous....

You've got a good point there, I guess it just depends on where you look, places like New York have lots of farmland but all the rocks were piled up into fences hundreds of years ago so it depends on how long the place has been cultivated and since there's few crops there would be little pesticide use. I still think the fungus is the cause of the disease but bats are the primary vector. Hopefully everyone is extra careful at the convention though (I'm not going since it's 2000 miles away from me but I'll probably go to 2012 and 2013 since they're close.) because if WNS suddenly pops up in Colorado next winter it's going to be really hard convincing people that humans are not spreading the disease. I do think as it spreads south it will be less severe in terms of percent mortality due to warmer temperatures, but total bat losses will be greater since the southwest has some humongous colonies.