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It’s reminiscent of the beginning of an old-school horror movie. As the sky darkens, several vehicles pull up to an abandoned house in a rural area. Armed with flashlights, they wade through waist-deep grass toward the building, as cows moo softly somewhere in the distance. As the last of the light fades, creatures begin to leave the house, flying low and swooping into the night sky to feed.

But unlike a horror movie, the only thing truly scary about this scenario is the danger that these creatures are in. That’s because they’re bats. Bats are facing multiple threats to their populations, and the people approaching their home (the abandoned building) are biologists who want to find out more about how they are doing. Every year, Washington Department of Fish and Wildlife biologists in various areas around the state do bat surveys to assess bat populations.

Importance of bats to environment and economy

Washington is home to 15 bat species: the big brown bat, California myotis, canyon bat, fringed myotis, hoary bat, Keen’s myotis, little brown myotis, long-legged myotis, pallid bat, silver-haired bat, spotted bat, Townsend’s big-eared bat, western long-eared myotis, western small-footed myotis, and Yuma myotis.

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Little brown bats (Myotis lucifugus) are the most commonly seen bat in Washington and weighs about the same as a nickel.

While some people are not big fans of bats because of the “old wives tales” that they turn into vampires or fly into people’s hair, bats in reality are extremely beneficial to humans. They make up a large part of our ecosystem and economy. By eating pests like mosquitoes and beetles, bats don’t just protect you from bug bites — they also provide an estimated benefit of nearly $4 billion annually to the U.S. agricultural industry by providing free pest control.

White-nose syndrome — a devastating bat disease

Like many wildlife species, bats are threatened by habitat loss, climate change, and disease. They are particularly vulnerable to white-nose syndrome, a fungus-caused disease specific to hibernating bats. White-nose syndrome is estimated to have killed millions of bats in eastern North America since 2006 and can kill off entire bat colonies during hibernation.

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Map of white-nose syndrome spread across North America since 2006. For more information, visit whitenosesyndrome.org.

The first case of white-nose syndrome in the western U.S. was confirmed near North Bend in western Washington in 2016. This map shows that its presence has since been confirmed in King, Pierce, and Kittitas counties and the fungus that causes the disease has been found in those counties as well as in Lewis, Chelan, and Snohomish counties. It is unclear at this time how white-nose syndrome will impact bats in our state over time as Washington’s bats do not hibernate in as large of groups as eastern North American bats. This difference in behavior could potentially slow the spread of white-nose syndrome here.

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Biologists can use Ultraviolet (UV) light in the field to detect the fungus that causes white-nose syndrome. Infected bats usually have an orange glow on their wings as shown in this picture.

The fungus that causes white-nose syndrome (Pseudogymnoascus destructans) can grow on the nose, wings, and ears of an infected bat during winter hibernation, sometimes giving it a fuzzy white appearance. Even if the fungus is not visible, it can still invade skin tissues and cause extensive damage. Affected bats wake more often during hibernation, which causes them to use crucial fat reserves, leading to possible starvation and death. Effects of the disease can also include wing damage, inability to regulate body temperature, breathing disruptions, and dehydration.

Counting bats to monitor populations

Annual population surveys are important to monitor the health of our bat populations. Every year in late spring and early summer, biologists take to the night shift to sit outside 22 known bat colonies across the state, like this old abandoned home that was slowly taken over by bats. These colonies can be in a cave, an old mine, a hollow tree, stone wall, or abandoned homes or buildings.

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Abandoned home that is now a roosting place for bats.

The team of biologists and volunteers position themselves around the colony, each assigned to watch a known exit from the structure where the bats sleep during the day. A red light and sometimes night vision gear help to spot the animals as they emerge. Unlike in Dracula movies, the bats don’t all leave the colony at once in a large cloud of flapping wings. They tend to go one or a few at a time, making it easier than it sounds to count them. Armed with a clicker, the counter clicks the hand-held device every time they observe a bat leave from their assigned exit. While it’s not an exact science, this method gives a good indication of overall numbers and colony changes over time.

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Left: Colony of bats in abandoned building. Right: A bat takes off into the night sky.

How to be a bat hero

Learn more about Washington’s bats on our website, including what to do if one or more gets into your home, how to encourage bats to roost on your property, and how you can help in the fight against white-nose syndrome. Review the tips below on other ways you can be a bat hero.

  • Report groups of bats you see using the online observation reporting form. This information will help us understand our bat populations and monitor white-nose syndrome in Washington.
  • Do not handle live bats. If you have found a sick or dead bat, please report it using the online reporting form and contact the closest wildlife rehab facility.
  • Avoid entering areas where bats may be living to limit the potential of transmitting the fungus that causes the disease and disturbing vulnerable bats. Do not allow pets to access areas where bats may be roosting or overwintering as they may carry the fungus to new sites.
  • Get involved in bat conservation! Help improve bat habitats by reducing lighting around your home, minimize tree clearing, and protect streams and wetlands. Try to incorporate one or more snags into your landscape, keeping old and damaged trees when possible. Snags provide important habitat for bats and other backyard wildlife.

Wild Washington lesson for high school students

Oct. 24–31 is #BatWeek, and now more than ever bats need our help! Check out our latest Wild Washington lesson plan for high school students, and share with the educators, parents, and students you know.

In this lesson, students will describe the economic and ecological importance of bats and identify anthropogenic impacts to bat populations. They will research, analyze and evaluate credible sources and use these sources to create a service-learning project centered around helping bat populations. The lesson aims to empower students and help them learn new skills as they explore potential careers.

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The Washington Department of Fish and Wildlife is dedicated to preserving, protecting and perpetuating the state’s fish and wildlife resources.

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