Within five years the death toll of North American bats succumbing to "white-nose syndrome" has reached the one million threshold. Now, the causative fungus Geomyces destructans has been identified in a number of European countries -- so far without detrimental effects for the native bat populations.
This is one of the most important results of a collaborative study by researchers from Germany, Switzerland, Hungary and the United Kingdom coordinated and carried out by the Leibniz Institute for Zoo and Wildlife Research (IZW) in Berlin, Germany. Will these findings help to tackle one of the major crises in nature conservation?
Since 2006 unprecedented mass mortalities have been recorded in North American hibernating bat populations. More than a million animals died and the scale of the problem continuous to increase. Initially the first dramatic declines remained within the northeastern states of the US, then spread in a radial fashion to neighbouring regions. This year the Canadian border was breached. Cause of the mass mortalities is a fungal infection. In Europe, concerns are rising that this fungus might be transferred to the European continent and then might possibly pose a similar threat to native bat species here.
Now a collective project by researchers from Germany, Switzerland, Hungary and the United Kingdom, the mycology department of the hospital of Munich Technical University, the Robert Koch Institute and the IZW shows that the fungus Geomyces destructans actually occurs in several European countries -- the only previous record was that of a single bat reported from France. The scientists also unearthed early reports indicating that the fungus was already noted on hibernating bats in Germany 25 years ago. "So far it seems that a colonisation by the fungus has no detrimental effect on European bat species," says IZW project leader Dr. Gudrun Wibbelt.
The results of this study on white-nose syndrome have just been published in the scientific journal Emerging Infectious Diseases. The involved researchers investigated more than 350 hibernacula in different European countries and found 21 animals carrying the fungus. Typically, bats have distinctive small white fungal patches around their nose and wing membranes which lead to the denomination white-nose syndrome. The fungus belongs to the group of cold-loving fungi which preferably degrade keratinous materials like flakes of skin or hair. In North America, the fungus causes severe tissue destruction in bats which then subsequently can lead to the death of the animal. The previously undescribed fungus was identified for the first time in 2008 in the USA. American scientists are certain that the mass mortalities are directly linked to this new emerging fungal infection.
"Surprisingly, comparative molecular genetic analyses revealed a 100% identity between gene segments of the North American and European fungal strains. Now the most important task is to understand why European bats do not die after being colonised by the fungus. Hopefully this will give a lead to rescue their North American relatives -- or at least to prevent the fatal fungus being brought into Europe. All investigations aim to protect bat populations in Europe as well as in North America," says Wibbelt.
In the last winters in the US, bats displayed aberrant behaviour during hibernation, leaving their cave roosts during daytime and hundreds of dead animals were found in the snowy surroundings. There are well known caves where bat species with previously abundant populations are decimated by 80 to 99 % and in some regions bats are now threatened with extinction. This development is reminiscent of the recently newly emerged fungal infection chytridiomycosis in amphibians, where a fungus invades the skin of frogs. This infection is responsible for a global decline of numerous amphibian species.
In Europe, about 40 different insectivorous bat species occur. The smallest weighs 4g only, the largest has a wing span of more than 40cm. Almost all European bat species are endangered and protected by nature conservation legislation. Bats play an important role for the environment as their nightly hunting forays markedly reduces the number of pest insects which are their major food source. Bats therefore possess an unequivocal ecological and economic value as they not only help to cut down pesticide usage but also increase the number of healthy plants.
Currently, researchers in Europe and North America are urgently trying to elucidate the white-nose syndrome and understand why European bats seem to be resistant against the fungus.
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