Double, double, toil and trouble!

The witches of Shakespeare’s Macbeth threw several of our forest creatures into their witch’s brew:

Fillet of a fenny snake,
In the cauldron boil and bake;
Eye of newt, and toe of frog,
Wool of bat, and tongue of dog

But this Halloween, some of these creatures have threats other than being mixed into a potion to worry about: disease. For the bat population, white nose syndrome (WNS) represents a fate scarier than any vampire attack or witch’s brew.

The big brown bat is one of the species of bat at risk of white nose syndrome.
The big brown bat is one of the species of bat at risk of white nose syndrome. Credit: U.S. Fish and Wildlife Service

The fungal disease, named for the white fungus that appears on the bat’s nose, ears, wings or tail, causes strange behavior in bats. They may leave their cozy hibernation spot and fly outside during the day in the cold winter months. Often, affected bats may cluster near the entrance of the cave.

WNS has already cost the lives of around 6 million bats in eastern North America. If we lose these creatures, we’re losing much more than beloved symbols of Halloween. Bats play several very important ecological roles, including insect control.  A single, pregnant bat can eat as much as its own weight in insects in a single night. By consuming insects that are harmful to agriculture and forests, bats are estimated to be worth billions of dollars to the agricultural industry. Bats are also important pollinators and seed dispersers. When viewed in the context of declining bee populations, the combined threat to some of our major pollinators is concerning, indeed.

So, while there’s no need to fear bats this Halloween, there may be cause to fear their dwindling numbers as WNS continues. Scientists are still learning about the causes of WNS and how it is spread, but there is evidence that humans may play a role in spreading the disease — which has so far been shown to have no effect on people — when we enter the places where bats are hibernating. Even absent the disease, disturbing bats during hibernation is a big problem, as they will then waste some of the precious stored energy they need to survive the winter. Bats disturbed during hibernation may not make it to the spring.

Learn more about white nose syndrome and how you can help at

And have a Happy Halloween!

Bats. Credit: Stuart Anthony