Blane Klemek column for August 2: Up-close view gives insights into bats
If ever you get the chance to observe a flying bat in good light conditions, grab your binoculars and enjoy the show. You'll be glad you did.
Of all the occasions that I had watched bats in flight -- be it large numbers of them scooting and darting over a body of water, or a single bat zigzagging this way and that over my backyard -- until recently, I had never thought about observing them through the optics of my binoculars.
Once last summer, while walking on one of my trails along the edge of the woods adjacent to tiny Lake Assawa, I stopped to watch a little brown bat flying across the shallow waters above the cattails. As my eyes followed the bat for a couple of minutes as it hunted for flying insects, it suddenly occurred to me to run to my house and retrieve the binoculars. If I was lucky, I thought, the bat would still be flying in the same area when I returned.
What I was privileged to observe is exactly how "batologists" describe a bat engaged in the act of hunting and capturing prey. As a bat homes in on a moth or other flying insect, it doesn't always capture the meal in its open mouth, as some birds do. More frequently, as was the case with my bat, a bat scoops the insect into its tail, and, without missing a wing-beat, the bat grasps the insect with its teeth and eats its meal in midair.
It was fascinating watching the small bat as it pursued its insect meals. That zigzag, up-and-down flight pattern so typical of flying bats are indeed bats searching, locating, chasing, capturing and feeding on a host of flying insects. My binoculars brought everything into incredibly vivid, up-close images that were surprisingly easy to follow.
Bats, as almost everyone knows, are the only mammals in the world that can achieve true flight. They are represented by many different species occupying a variety of habitats all over the world. Here in Minnesota, seven species are known to exist: big brown bat, little brown myotis, northern myotis, eastern pipistrelle, hoary bat, silver-haired bat and eastern red bat. More than 900 species occur worldwide.
All of Minnesota's bats are insectivores. That is, their entire diet consists of exclusively insects. And contrary to popular belief, mosquitoes, though indeed consumed, are not the only insects they feed on. Bats seem to prefer mostly soft-bodied insects, especially moths, as well as mayflies, midges, caddisflies, lacewings, leafhoppers and, of course, mosquitoes. Other insect prey includes many different species of beetles, bugs and even spiders.
It has been estimated that a bat can capture and consume as many as 1,000 insects in just one hour. Perhaps that figure sounds a little excessive, but anyone who has ever watched bats flying, darting, diving and abruptly turning, twisting, and maneuvering on the wing as they hunt for prey knows that this is indeed a possibility.
Some people believe that bats cannot see at night. The often used expression "blind as a bat" is a curious statement, given the fact that bats can fly and capture insects in total darkness without any difficulty whatsoever. And while bats can and do see with their eyes, prey is located primarily by echolocation.
Simply put, high-frequency sounds are emitted by bats, which travel through the air. When the sound waves encounter, say, a moth, the waves bounce back to the bat's ears. In this way a bat can home in on a flying insect meal by listening, basically, instead of seeing. These high frequency pulses produced by hunting and flying bats are inaudible to our ears and can occur at as high a rate as 200 pulses per second.
One of the craziest myths that persist about bats is that they get caught in people's hair. Like dragonflies darting above our heads as they nab pesky gnats and flies during the day, I for one don't mind a bat zooming above me as it captures equally annoying nighttime insects. While perhaps unsettling to some, bats know the difference between us and a hapless moth or midge. The little flying mammals are only interested in a tiny meal and will avoid colliding with objects both stationary and mobile.
We have nothing to fear from bats; they are harmless, beneficial insect-eating creatures that are scarcely noticeable (unless, of course, they choose to roost in our attics or other buildings).
A researcher studying big brown bats estimated that a colony of 150 individual bats could eat enough cucumber beetles throughout a summer to effectively reduce the population of egg-laying larvae by as much as 33 million.
So, before summer's end, walk to a nearby lake or river, look up at your yard light or the streetlights in town, or take a twilight walk in the park or countryside and look around for bats in flight.
And be sure to take your binoculars with you as you get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org