Batty About Bats (Part 1) Listening and Learning

It’s Bat Week!

Just in time for Halloween, a whole week devoted to bats. Thin leathery wings. Oversized ears. Pointy teeth. Silent nocturnal flight.

Do bats give you the heebie-jeebies?

Not me! This is the story of how I fell in love with bats.

This summer at John Heinz National Wildlife Refuge, I had the privilege of helping biologist Brendalee Phillips conduct a bat population survey. We wanted to learn which species of bats are found at the Refuge.

More on that in a minute. First, a word about bats.

Many people find bats creepy. Misconceptions and superstitions abound. Let’s set the record straight: far from being blind, disease-ridden, blood-sucking pests, bats are gentle, intelligent creatures who protect us from diseases and pests.

Big Brown Bat
(Photo: Ann Froschauer/USFWS)

And bats are vital to our environment, our farmers and to us. Which is why there’s a whole week devoted to singing their praises.

Bats are highly beneficial to humans because of what they eat. Some species eat fruit and nectar, and are important to plants and agriculture for seed dispersal and pollination.

Many more bat species, such as the ones in my area, are insectivores. Each bat eats thousands of insects a night, saving farmers millions of dollars a year on pest control, and protecting us from disease.

Some estimates say bats provide over $50 BILLION worth of pest control services worldwide.

Amazingly, bats can locate the tiniest of flying insects in total darkness. Contrary to myth, their eyesight is good, but that’s not how they find bugs.

Visual representation (sonogram) of a bat echolocation call. (Screen capture from SonoBat software)

They hear them.

Our local bats hunt and navigate by echolocation. When flying, a bat emits a steady stream of rapid high-pitched calls, much higher than human ears can hear. Those sound waves travel out, hit an object or insect, and bounce back to the bat.

Subtle variations in the sound tells a bat what’s out there, and where.

That’s how we figured out which species of bats we have here at Heinz Refuge – we listened to them. But if their calls are too high-pitched for human ears to hear, how did we do that?

With this:

This is an acoustic monitor, specially designed to record sound in the frequencies bats use to echolocate.

We placed the monitors in 9 different locations throughout the Refuge at three different times during the summer, corresponding to different phases of the bats’ life cycle. Microphones recorded any nearby bat all evening, for three or four consecutive nights.

Life is seldom straightforward, and this project was no exception. We had any number of glitches. Sessions that mysteriously had no data. Dead batteries. Malfunctioning microphones. Lawn mowers.

Wait – lawn mowers?

Alas, one of our recorders lost a battle with an overgrown garden tool, just before a heavy rainstorm. When the monitor was rescued, it gave us no data – but it did offer up a gallon of water and three crickets.

Thus I learned my first lesson about field work: it rarely goes smoothly. It requires flexibility and persistence. Not to mention bug spray and lots of paper towels.

After each recording session, we had a handful of memory cards filled with ultrasonic bat calls. Now what? How did we figure out which species of bats were recorded? Why were we surveying bats in the first place?

Stay tuned for the answers as Bat Week continues!

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