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11 facts about Minnesota bats and a mystery plague that threatens them

A little brown bat exhibiting symptoms of white-nose syndrome.

On a beautiful winter’s morning last Saturday I drove north to St. Croix Falls for a program on white-nose syndrome, joining more than 60 other citizens concerned about this threat to Minnesota’s bat populations.

This is a topic I have been interested in, but had not gotten around to studying, since a visit to Wind Cave National Park in South Dakota in the fall of 2012, where we were questioned closely at the welcome center about any visits we might have made to other caves or mines in the previous five years.

This longevity of the white-nose fungus spores was impressive, as were the awful statistics about mass bat die-offs in the eastern United States. Then came the news last August that the fungus, recently renamed Pseudogymnoascus destructans, had turned up on bats in Minnesota.

Here are the 11 most interesting things I took away from Saturday’s talk by Gerda Nordquist, the Minnesota Department of Natural Resources‘ bat specialist (and from some further reading she inspired me to do), starting with the few bits of good news:

1. The fungus doesn’t always bring immediate catastrophe. Although Pseudogymnoascus was found in swab tests on bats at two Minnesota locations — Forestville/Mystery Cave State Park near the Iowa border, and Soudan Underground Mine State Park near the Canadian border — bats in those places did not show signs of the disease itself (contrary to some early news reports).

Nor were fungus spores found elsewhere in these caves.

For reasons that remain unclear, not all bats exposed to this skin-eating fungus will develop the syndrome’s horrific lesions on their nose and wing tissues. At sites in Vermont and Missouri, bats have remained disease-free for four years or longer in the presence of the fungus.

Although white-nose syndrome is known to have killed as many as 7 million bats since 2006, with mortality rates over 90 percent in some infected caves, even bats that are seriously weakened by the syndrome will sometimes recover after emerging from hibernation.  (Pseudogymnoascus is a cold-loving fungus and afflicts bats that overwinter in caves, mines, sewers, culverts and similar locales; migrating bats appear to be unaffected.)

And in Europe, species essentially identical to the North American types being decimated by white-nose syndrome disease are untroubled by the fungus, possibly because they co-evolved with it.

2. Still, the trend lines are awful. Since 2006, when white-nose syndrome was first detected in a cave near Albany, N.Y., the fungus has been found in 22 states and 5 Canadian provinces, and bats have developed the syndrome in all but three of these. (So far the fungus has skipped over Wisconsin, a peculiarity a fellow Wisconsinite in the audience attributed to our governor’s repellent properties.)

The U.S. Fish and Wildlife Service is predicting regional-scale extinction of the little brown bat within as little as a dozen years. The little brown bat, big brown bat, northern long-eared bat and tri-colored bat are the Minnesota species at risk from white-nose syndrome; the non-hibernating, migrating species — hoary, red and silver-haired bats — are not afflicted.)

3. Some migrating bats in Minnesota winter as far afield as Mexico, according to banding data.

4. Bats make cool, almost musical sounds with their radar rigs. In addition to the chirping we can hear without special gear, the ultrasonic clicking sounds made by bats for purposes of echolocation can be rendered audible to the human ear with electronic equipment that Nordquist and her researchers use to count and track bats.

She played a clip of an echolocating big brown bat that sounded to my amazed ear like a Caribbean percussionist; you can find a similar sample here.

Bats clearly listen for one another as they navigate a summer insect swarm, Nordquist said; whether they endeavor to call out in this way is not known.

5. Bats are important to ag systems, not just ecosystems, in ways that go well beyond their oft-discussed role as important pollinators.

Some 70 percent of bat species, including all those in Minnesota, are insectivores and consume massive quantities of insect pests. Nordquist quoted one set of calculations holding that bats may save Midwestern farmers between $3.7 billion and $5.3 billion a year in avoided pesticide costs.

They are also excellent dispersers of seeds.

6. However, ag systems may not be as kind to them. Of all the bright questions from Saturday’s audience, perhaps the most insightful was whether pesticides might be rendering North American bats newly vulnerable to the Pseudogymnoascus fungus, in the way that certain insecticides may be making honeybees suddenly more vulnerable to parasites they have endured for decades.

That’s a subject that needs more research, Nordquist said, but it’s certainly a strong possibility. Patterns of white-nose syndrome look very much like those of an immune-suppression disease,  and insecticides have been known to promote these in other species.

7. Breeding disease-resistant bats isn’t a solution, Nordquist said in answer to perhaps the dumbest question from the audience, advanced by your correspondent, still thinking about the honeybees.

The selective breeding techniques being explored as a way of getting honeybees past colony-collapse disorder can’t really work with bats because “they resist captive breeding,” Nordquist patiently explained. Also, they don’t live in hives, and are difficult to herd.

8. That decontamination foam you have to walk through to visit a bat cave these days? Woolite! And it does kill Pseudogymnoascus spores, Nordquist said.

However, it remains highly unclear how the spores are spread from cave to cave, so getting tourists and spelunkers to decontaminate their boots and clothing is more of a common-sense precaution than a proven quarantine strategy.

One other — and heartbreaking — possibility is that bat researchers have been transmission agents, too.

9. New research holds out hope of controlling Pseudogymnoascus with biological agents, including a project at Georgia State University to see if a naturally occurring bacterium can be used to fight the bat-killing fungus without introducing all the risks associated with chemical fungicides.

Indeed, Nordquist said, one possible explanation for disease-free bats in places like the Soudan mine, as well as the Vermont and Missouri hibernacula, is that some other organism is exerting helpful biocontrol.

10. In the meantime, there’s little that governments and citizens can do to help the bats.  Re-opening bricked-up caves along Minnesota rivers isn’t a good option, Nordquist said in answer to a question, because it’s hard to come up with a barrier that lets the bats in but keeps the vandals out.

“Closing off a cave with gates is a gauntlet the vandals just love to take on,” she said. “They spend incredible amounts of energy to defeat our gates. And caves are dangerous places.”

11. But if you should happen to see a flying bat this winter, report it to the DNR, because it’s mostly likely a hibernating bat that has been roused by some annoyance — and that annoyance could well be white-nose syndrome.

* * *

Saturday’s presentation was the first in a spring series sponsored by the St. Croix River Association and the National Park Service.

Resources for further inquiry:

Comments (2)

  1. Submitted by Tom Anderson on 01/21/2014 - 09:25 pm.

    Bat gates

    Given their success in many places in the U.S., it seems like there should be a version that would work in the Twin Cities. I believe that some of our own state parks use them (along with the signs telling people to stay out). If some of the old closed up caves were once used by bats it might well be worth opening one or two up to see if the bats might return.

    And don’t forget the damage that wind turbines are doing to our bat population. There has been some cooperation and progress between turbine owners and bat conservationists which is good news, but agriculture systems aren’t the only things killing bats.

  2. Submitted by Lance Groth on 01/23/2014 - 05:28 pm.


    While I recognize the importance of doing thorough research and not jumping to conclusions, it is also clear that Big Ag and pesticide manufacturers are running the show in America. For my part, the evidence against neonic pesticides is compelling enough to justify a ban. Many argue that, in the case of colony collapse disorder, the bees are being afflicted by many diseases and parasites, so pointing to one cause is premature. But it seems pretty clear to me that these other problems all started ballooning when neonics went into widespread use, and this is because the neonics disable the bee’s immune system. As a beekeeper friend of mine likes to say, it should be called “bee AIDS”, because it is the collapse of their immune system that leads to death by many secondary causes.

    Given that bats feed on insects, and given the persistence of neonic pesticides in the environment, it shouldn’t be a surprise if the pesticides are also compromising the bat immune system (although, of course, since one is an insect and the other is a mammal, that is a big leap and confirming research certainly needs to be done).

    It seems to me that Big Ag and the pesticide industry are engaged in a death spiral. The combination of powerful pesticides and herbicides, and GMO crops with built-in pesticides, which result in the evolution of resistant strains, which require application of ever more powerful chemicals and in ever higher doses, can only lead to ecological catastrophe. It’s unfolding before our eyes, and we need to act preemptively while there is still time. Obama’s sorry excuse for an EPA is no help, as they only kowtow to business interests. Their leash was not loosened with the advent of a democratic president.

    Perhaps there is a thin thread of hope for the bats, though. Even if mortality is over 90%, as long as it isn’t 100%, it is possible that the survivors will breed their own resistant strain. If they aren’t driven below the threshold of viability first.

    I almost can’t read environmental news any more, as it seems to all be so dismally depressing. I hope we come to our senses while we still can.

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