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Fungal disease threatens western bat populations

Western states should introduce proactive conservation measures to protect their hibernating bat species

A newly published study suggests the fungal pathogen that causes white-nose syndrome (WNS) in hibernating bats has spread into several western U.S. states. Photo by Kim Raff
A researcher about to handle a hibernating Townsend’s big-eared bat in an abandoned mine in Nevada.
Photo by Kim Raff

A fungal disease that has killed millions of bats in eastern and central North America has made its way west.

A newly published study suggests the fungal pathogen that causes white-nose syndrome (WNS) in hibernating bats has, indeed, reached several western American states. The transmission, researchers say, is likely due to bat-to-bat spread and poses an imminent threat to western species.

First detected in 2006, WNS presents as a fungus growing on the nose and wings of a bat. The infection, researchers say, triggers a higher frequency of arousals from hibernation. These arousals involve an increase in body temperature from near freezing to an active mammalian body temperature, requiring a significant amount of energy.

Bats, researchers say, have limited fat stored for the winter. If this is used up prematurely, death by starvation occurs.

To determine which species faced high mortality and risk of extinction if infected with the disease, researchers combined field data collection a mechanistic model that explains how bats consume energy during hibernation and how the fungus impacts this consumption.

Spanning a period of three years, the research team looked at 946 bat captures (all released after measuring), collecting data from nine different species and predicting the survival outcomes for each.

The study revealed threats to all small Myotis species examined, including M. ciliolabrum (western small-footed bat), M. evotis (long-eared bat), M. lucifugus (little brown bat), M. thysanodes (fringed myotis), and M. volans (long-legged bat), as well as Perimyotis subflavus (tricolored bat). By comparison, larger species (including the cave bat, Townsend’s big-eared bat, and the big brown bat) were predicted to be less impacted by WNS.

“This study demonstrates the value of collecting baseline data to preemptively understand a threat posed by a wildlife disease, like white-nose syndrome to western bats, so more proactive conservation measures can be taken to protect these species,” says principle investigator, Sarah Olson, PhD. “Here, an all-hands-on-deck approach is needed. Western states can take steps now to put protections in place before anticipated severe declines are observed, like reducing habitat loss and restricting access to hibernacula, as well as investing in research and surveillance.”

“Our results indicate the need to take a holistic view on conservation, as it is not just one thing that determines survival from white-nose syndrome, but rather the combination of bat, environment, and disease variables,” adds the study’s lead author, Catherine Haase, PhD.

The findings of the four-year study have been published in Ecology and Evolution. To access the report, click here.

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