BU Scientists Release Alarming Data on Bat Depopulation

August 6, 2010

A new study led by Boston University College of Arts & Sciences researchers predicts that one of North America’s most common bat species will be all but extinct in 20 years. A team including BU Postdoctoral Researcher Winifred Frick, NSF Bioinformatics Postdoctoral Fellow at UC Santa Cruz and BU, BU Professor of Biology Thomas Kunz, and former BU PhD student D. Scott Reynolds (GRS’98) recently released a study documenting the rapid depopulation of little brown myotis, previously one of the most common bat species in North America. This species’ rapid population loss is being caused by an emerging disease affecting hibernating bats in eastern North America. The disease, called White-Nose syndrome (WNS), was first discovered in 2006 in New York State. WNS currently affects at least seven species of bats, including the little brown myotis. The group’s findings will be published as the lead story in the August 8 edition of Science magazine, with Frick the lead author of the paper.

The researchers used past data on bat population growth as well as current data on depopulation due to WNS to simulate the effect of WNS on brown myotis populations over the next 100 years. Even if disease mortality lessens over time, the regional population is expected to collapse from an estimated starting population of 6.5 million bats to less than 65,000 (i.e. 1% of the pre-WNS population) in less than 20 years. Such a severe population decline, especially if the disease spreads further south and west of its current distribution in eastern North America, may result in unpredictable changes to ecosystem structure and function.

WNS is associated with a newly described psychrophilic fungus (Geomyces destructans) that grows on exposed tissues of hibernating bats, apparently causing premature arousals, aberrant behavior, and premature loss of critical fat reserves. The origin of WNS and its putative pathogen, G. destructans, is uncertain. A plausible hypothesis for the origin of this disease in North America is introduction via human trade or travel from Europe, based on recent evidence that G. destructans has been observed on at least one hibernating bat species in Europe.

WNS has spread rapidly and now occurs throughout the northeastern and mid-Atlantic regions in the U.S.A and in Ontario and Québec provinces in Canada. Many species of bats in temperate North America hibernate in caves and mines in aggregations of up to a half-million individuals in a single cave. In late spring, these winter aggregations typically disperse into smaller sex-segregated groups of conspecifics, when adult females form maternity colonies and adult males mostly roost alone. From August to October, females and males assemble at hibernacula or swarming sites to mate prior to hibernation. The mechanisms for persistence and transmission of G. destructans during summer and fall months are unknown, but spread of the fungus to new geographic regions and other species may result from social and spatial mixing of individuals across space and time.

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