From the Vault: Anabat

By Eilene Lyon

At the end of my freshman year at Fort Lewis College, in 2005, I did a 10-week internship in the Natural Resources department at Mesa Verde National Park. One of the full-time employees, Marilyn Colyer, invited me to join a bat survey in the La Plata Mountains.

Though wandering the forest at night is not my favorite thing, bats became a bit of an obsession. The principal tool we used was an Anabat, which allowed us to record echolocation calls, rendering them audible and visual, in the form of a graph. Part of my job was to study the graphs and determine which species we had observed.

An Anabat graph I worked with at Mesa Verde. This one is for a Mexican free-tailed bat.

Bats fascinate me for several reasons. They are the only mammals capable of true flight. Like us, they have a low reproductive rate, generally no more than one pup per year. They are long-lived, as much as 25 years in the wild. No mammalian order other than Rodentia boasts as many species, and bats (Chiroptera—“hand-wing”) are more varied in morphology and life strategies.

You can see from this bat skeleton why they are called “hand-wing.” They have essentially the same arm and hand bones as we have, but the forearm and fingers are elongated to enable their flight. (Wikimedia Commons)

Large, diurnal fruit-eating bats, aka flying foxes, use their eyesight exclusively to forage. Smaller, nocturnal bats use echolocation—a high-volume, high-frequency burst of sound—to forage, but their eyesight in daylight is as good as ours. Hence the phrase “blind as a bat” is patently ridiculous.

There are 18 species of bats known to live in or migrate through Colorado. All are insectivorous and nocturnal. Of these, the most common are Mexican free-tailed (Tadarida brasiliensis), big brown (Eptesicus fuscus), little brown (Myotis lucifugus), and silver-haired (Lasionycteris noctivagans).

The most endangered is the Townsend’s big-eared bat (Corynorhinus townsendii). White-nose syndrome, a deadly fungal disease, finally reached southern Colorado this past summer. A single bat at Bent’s Old Fort tested positive. The disease has killed millions of bats nationwide, thus we need to be concerned.

The Townsend’s Big-eared bat. (Wikimedia Commons)

The summer before my senior year, my field ecology class had the opportunity to camp out for a night, just across the state line in New Mexico. We observed a scientist mist-netting bats near a stock pond in the desert. When bats leave their roost at night, their first task is getting a drink of water. Though we were not permitted to participate in the mist-netting, one lucky volunteer (me!) got to briefly hold and release a silver-haired bat.

With Marilyn’s encouragement, I decided to do a bat study for my senior thesis project. To do so, I needed an Anabat of my own, since the college did not have one. Fortunately, I got some grant money to help purchase this one. The technology has improved since 2007, so it is essentially obsolete. And software now does the work of “reading” the graphs to determine species.

Little brown myotis. (Wikimedia Commons)

What the machine is still good for is listening to bats in real-time. Their echolocation calls fall in the 20–100 kilohertz (kHz) range, while our hearing is in the 20 Hz–20 kHz range. It’s actually a good thing we can’t hear them, because the volume would be deafening. Bats avoid injuring themselves by dislocating the bones in their inner ears when they call. By instantly analyzing the echo, they can detect an object no bigger than the width of a human hair.

The Anabat uses a division process to bring the bat calls into our hearing range. The microphone is so sensitive that it will pick up the sound of your fingerprint whorls rubbing together. It’s fun to take along on a camping trip, or even using here at home in the summertime when I see bats foraging in the dusk near our deck.

As with any other being, the more we know and understand about bats, the more likely we are to fight for their conservation. Though they offer services that make the world better for humans (like eating mosquitoes!), they deserve to live their lives for their own sake, without interference from us, without our destroying their habitat.

For more on bat sounds, visit this Ohio State University page.

Feature image: The Anabat II with separate recording unit.


Feldhamer, George A., Lee C. Drickamer, Stephen H. Vessey, and Joseph F. Merritt. Mammalogy: Adaptation, Diversity, Ecology. 2nd ed. New York, NY: McGraw-Hill, 2004.

Adams, Rick A. Bats of the Rocky Mountain West: Natural History, Ecology, and Conservation. Boulder: University Press of Colorado, 2003.

Colorado Public Radio news

Colorado Parks & Wildlife: Bats in Colorado

42 thoughts on “From the Vault: Anabat

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  1. I’ve always been afraid of bats—ever since going to sleepaway camp and being told that they attack you and get tangled in your hair. I assume there’s no truth to that old horror story.

    Liked by 2 people

    1. I do wonder how that got started. I think many people have heard that. Only a rabid bat would be likely to behave that way. You’re more likely to encounter a rabid fox or skunk, though. I’ve never seen or heard of a bat attacking someone. There are vampire bats (not in the US) that could sneak up on you and take a little blood from your ankle – like an oversized mosquito.

      Liked by 2 people

  2. Bats always creeped me out. But damn if they aren’t the most intriguing creatures! I didn’t know the half of it until I had one come into my house back in the day. I was freaked, but I also remembered what happened the time my parents had called a service to remove a bat that had flown in their house. It didn’t end well. So what I did was close all the doors, locking my cat in one, and opened the front and back doors and then I went hunting. I equipped myself with a baseball cap over which I put a beanie, and goggles. It was taking me forever and then my lady friend got there and saved the day. In heels and curls akimbo, she drew the bugger out. I think he loved redheads but I’ll never be certain . . .

    Liked by 3 people

    1. Well they aren’t as colorful as bird, and since they’re nocturnal, usually hard to see. But they’re sort of like a miniature doggy with wings. The only one I ever found inside the house was long dead. I don’t know what happened to it. Found it under some shelving units in a closet in the garage. We get them roosting under our deck and sometimes in the closed patio umbrella. The coolest bats I’ve seen were the fishing bats of Ecuador.

      Liked by 2 people

    1. That’s great, Joy. We’ve long had bats at our house. When we replaced the siding with stucco, we put up a bat house, but none ever moved in. They eventually found space under the deck they liked. For all I know, it’s the same ones every year, they live so long.

      Liked by 2 people

  3. Wow! This is so fascinating. I love bats. I remember on one of our Brownie camps taking the girls out at dusk to observe the bats. I was trying to help them see that bats weren’t something to be feared. One year when teaching grade 3, we studied bats and then “adopted” a bat through a program in the States. It would have been fun to have had an Anabat. I did not realize that they can detect an object no bigger than the width of a human hair!

    Liked by 3 people

    1. That’s fantastic, Heather! I’m so glad you were teaching them about bats and that they aren’t to be feared. That fact about the size of an object they can detect I had forgotten and found when fact-checking in my old mammalogy textbook. Their echolocation skill is so impressive, as are their acrobatic flying abilities.

      Liked by 3 people

  4. What fascinating creatures. I had to rescue a bat from my friend’s house once (she lives in the country). It flew in her back door and landed on the curtains. She and another friend locked themselves in the bathroom screaming while I got rid of it in the same way as I would a big spider: Tupperware over the top, then slide the lid or a piece of paper gently underneath. For a hardened rural dweller with farming relatives I thought this was a strange reaction!

    Liked by 2 people

    1. I wonder how we come to fear certain things. The first time I met someone who was terrified of butterflies and moths, I was incredulous. But I’ve met others since then who are also quite seriously terrified of them, so I know it’s a real thing.

      Liked by 1 person

  5. I have never encountered a bat before, but would like to see one from afar. I just read about the fungal disease which turns their nose tips white and if I recall correctly, is wiping out 95% of the population. They made the list of endangered animals/birds species too late!

    Liked by 1 person

      1. Yes and I had just heard that story about how it happened so quickly for the poor bats. We have deer Chronic Wasting Disease here in Michigan. Once deer are afflicted, there is no remedy, so they die. All hunters are aware of it before archery and firearms season (the latter just ended on November 30th).

        Liked by 1 person

  6. When we visited Austin, TX, years ago, there was a large bat colony under a bridge. We went a couple of times to see them come out. I remember there was a mighty strange smell with that many there. I probably wouldn’t be so adventuresome these days, but it is fun then. You’ve certainly done some interesting things in your young life. Applause!

    Liked by 1 person

    1. I’ve heard of the large Mexican free-tailed bat colony there, but haven’t seen it. I did go to see the one at the Orient Mine in the San Luis Valley. That’s the largest known colony of bats in Colorado, I believe. It really was too dark to appreciate the shear number, though.

      Liked by 1 person

  7. Many, many years ago when I still visited zoos (I don’t anymore) I remember being present at vampire-bat feeding time (I think at London Zoo). The zookeeper bared his arm and a bat fed from it. Odd and a wee bit creepy. I always thought that was a very strange way to feed them! But probably just put on for show.

    I love the faces of flying foxes, but have never liked to look at the others. That said, I do appreciate them. Here in the UK, if we get bats in our roofs, we’re not allowed to remove them as they are protected. And we get little ones (probably pipistrelles) flying around our garden (yard) at night part of the year.

    I hadn’t realised they had good eyesight!

    I haven’t forgotten that I owe you an email. Will try to get to that soon.

    Liked by 1 person

    1. Hi Val, nice to see you here. The flying foxes do have cute faces. I also don’t go to zoos anymore. I find them depressing. I prefer to see animals in their native habitat. I’m glad that the bats are protected in the UK. They need all the help they can get!


  8. Bats are one of my favourite animals, so I loved reading about your experience. I’d like to take part in a bat survey! I actually want to volunteer for the Bats Trust to do bat rehabilitation, but I think you need to have quite a large space in your house for them to fly around in, which might be tricky.

    Liked by 1 person

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