Bats Reveal Life’S Ancient Secrets

The 1,100 species of bats make up 20 percent of all mammal species and a new book examines the threat posed to them by 60 million years of evolution

Pallid Bat

Pallid Bat

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EDITOR’S NOTE: This excerpt comes from the introduction and the afterward from Wild Guide Bats by Roundup News Editor Peter Aleshire. Stackpole Books has just released the book, now available at Amazon.com and many bookstores.

I settled myself on a boulder alongside the East Verde River, to watch the shift change.

Over the wide spot in the lazy stream, swifts veer, soared and plummet, maneuvering through little swarms of bugs — lacewings, caddis flies, mosquitoes.

Somehow I miss the first bat. But at some point, I realize that the swifts had changed. I looked more closely. They flutter more now, their flight more erratic.

Ah. The shift had indeed changed — the dwellers in the darkness had arrived to feast on the same bounty as the swifts. Of course, the composition of that buffet of insects had changed. The bats would chase down moths and a different crowd of beetles and a different hatch of winged creatures.

Big Brown Bats, I suspect. I didn’t have my little radio receiver to be sure. The receivers pick up the echolocation calls of the bats — screams inaudible to the human ear. The sound waves bounce off those fluttering insects and return to the extraordinary ears of the bats, maneuvering in the darkness with such astonishing skill that they can pluck a moth out of the air on the wing — guided by those echoes of sound.

Then again, maybe they’re Mexican Free-tailed Bats, which can gobble up their own weight in insects every night. That makes them invaluable to farmers. In a single night, a big colony of these bats can consume several tons of insect pests.

Tragically, their dependence on caves has proved fatal. In 1963, some 30 million Mexican Free-Tailed Bats formed the largest known bat colony in the world in Eagle Creek Cave in Arizona. Six years later, only 30,000 remained. Pesticides in their insect food poisoned them wholesale. And locals used to make a sport of taking shotguns out into the great roost caves and shooting into the dense swarms as they flew out of the cave in numbers that once darkened the skies.

Then again, maybe they’re Western Pipistrelles, who mingle freely with swifts at sunset, going for the same caddis flies and stone flies and leaf hoppers and flying ants and wasps that delight the swifts. Pipistrelles have beautiful, yellow fur — and black, wings, face and ears — like they’re up to something and traveling undercover. Solitary and mysterious — the females have the good sense to hang out in small groups with no guys in sight when it comes time to get down to the serious business of raising their twin pups. But I don’t think they’re Pipistrelles. Too big. The smallest North American bat, the Pipistrelles are about three inches long with eight-inch wingspans and weigh in at about two-tenths of an ounce at best.

I’m just guessing for the moment about the identities of these fluttery insect hungers. If I’d had my gear and it picked up calls at a frequency of 25 to 51 kHz, then I’d be sure it was a Big Brown Bat. The Pipistrelles squeak along at 47 to 55 kHz.

Of course, the moths know those frequencies also. Many species of moths have evolved their own radar detectors. When the bat’s locator signal hits them, they snap into dives and rolls by reflex — dramatically increasing the odds they’ll survive.

But, heck, maybe they’re Spotted Bats.

Then I won’t need a radar detector. If they just fly close, I’ll hear the clicking of their 8-12 kHz calls.

Biologists aren’t sure why the Spotted Bats use such a low frequency. Best guess is that those clever moths haven’t evolved a detector for bat cries at that frequency, so the Spotted Bats trade off a lower resolution for stealth.

I’ve been listening for that telltale click for years, for those Spotted Bats are large in my imagination — with their glossy black bodies, long silky hair and distinctive white patches on their throats and backs — all dressed up in the bat world equivalent of a tux — complete with a gleaming white cravat. Better yet, they have enormous ears — translucent, veined and a third of their body length.

But, I hear no click — have never heard the click.

Spotted Bats are rare throughout their range. No one knows why. The 1,100 species of bats make them second only to the 2.277 species of rodents for the most diverse of mammal species. Bats comprise nearly 20 percent of the 5,400 species of mammals on the planet. But most bat species are in trouble — especially in North America. A few species like the Big Brown Bat have adapted to the changes we’ve imposed readily enough — nesting in barns and attics and other structures. But bats mostly fit into particular niches. Caves that once harbored hundreds of thousands of bats in the winter have been disturbed or altered. We have only good guesses as to the cause of the declines that have pushed populations of some 40 percent of North American bats dangerously low. Have their bodies been weakened by the pesticides that build up in the bodies of the insects on which they depend? Have the species that migrate from the tropics up into North America every year suffered some carnage in the deforested tropics?

So I listen, always, in the darkness for the cry of the Spotted Bat. But I have never heard it.

I have struck up a whole new relationship with bats since writing a little field guide on the critters — and since settling here on the banks of the East Verde River.

Now I want to mount a bat house on the side of the house, stained a light color so it won’t absorb too much heat stuck up on the wall where it can get sunlight for about eight hours a day. Never occurred to me to build a bat box before I found out what we’ve done to the little fellows in return for their services. One recent paper in the journal Nature estimated that bats eat enough crop-devouring insects to save American farmers $24 billion annually in pesticides.

So now building a bat house seems like a moral obligation.

Besides, I don’t like mosquitoes.

Lord knows, I’ve tried. I know the little blood-sucking whiners have their role in the grand scheme of things. I just don’t like them. Can’t shake the feeling they’re out to get me.

So I’m hoping that a nice little maternity colony of one of the 28 species of bats found in Arizona will happen by, notice my welcome mat and take over the mosquito patrol.

Please note: An ambitious Big Brown Bat can gobble down 600 mosquitoes in an hour when he’s on a roll and the swarms are out and about.

I live in bat heaven, more or less.

The East Verde River runs year-round, nurturing a long, lush straggle of cottonwoods and sycamores and walnuts and ash. The bats love the sycamores, so smooth barked and white-boled sensuous, with a tendency to just naturally form interior cavities favored by the tree-loving bats.

Just the other night, I spotted a Hoary Bat — big, strong flier with sharp wings and a no-nonsense approach to dinner. They usually roost alone in trees. They overtake moths from behind, open their mouths and clamp down at just the right moment to get a nice mouthful, that doesn’t include the moth’s head or wings.

The bats love the river, as I love the river.

Up behind the house, the slopes rise steeply to a cliff of eroded limestone — laid down on some sea bottom 100 million years before the first bats flapped and 150 million years before our ancestors hit upon the opposable thumb — so useful in the building of bat houses.

I hiked up there with my nephew the other day. He ventured into a crevice that turned into a cave and reached up and put his hand right next to a slumbering bat.

Scared the holy what-not out of the poor lad. He came scrambling out of that cave in the rock like the abominable snowman was in hot pursuit.

We had a nice little talk about bats when he quit yelping and shuddering. I can’t tell you what species — since the lad didn’t think to make any useful observations beyond the sheer batness of the creatures. And I haven’t been back into the cave, not wanting to bother the neighbors. Soon, I’ve got to post myself up there at sunset with my bat detector and figure out what species I’ve got living in the rocks. I’m rooting for Townsend’s Big-eared Bats — big, yellowing fellows with giant, hairless ears. They establish maternity colonies in the summer, in which the womenfolk raise the kids without interference from all those irritating males — with whom they mated freely in the fall so they could store a nice selection of sperm for fertilization at their leisure. The Townsend’s with their droll, collapsible ears make a living flying through the trees and plucking large insects off the leaves and branches. I’d call that a daredevil way to make a living, maneuvering on wings thin enough to shine a light through.

The dusk is thick now, my favorite moment of the day. The river murmurs. The crickets tune up for the night. The lovelorn frogs take up the cue, happy, no doubt for the lack of frog-eating bats in the neighborhood.

The river smells of life, rich, damp, verdant.

I watch intently at the very edge of darkness, noting the last frantic dips of the hunting bats as the moths’ own radar detectors cause them to hurtle into evasive maneuvers. I note one pair of bats in the gathering gloom, one the shadow of the other. Ah, a chase — in which the second bat takes advantage of the flight of the moths from the teeth of the first bat to increase its own odds.

Six hundred mosquitoes an hour: Go for it, boys.

So I sit on the banks of the river as the water murmurs and the bats flutter. They each whisper ancient secrets — the key to life itself — if I only learn to listen.

I wish I had ultrasonic ears, like the leather-winged guardians of night. I wish that the flowers would glow in shades of echo and I could look into the dark with my ears and see the tracery of the moths in their urgent flight. Instead, I content myself knowing they’re there — and all life’s nested puzzles can be studied in the ancient dance of bats and moths all through the warm night.

At just this poetic moment, I feel the mosquito excavating a test hole in my cheek. I slap myself. Too hard.

I shake my head ruefully. Gotta get to work on that bat house.

EDITOR’S NOTE: Wild Guide Bats is available through Stackpole Books or Amazon.com. Other books by Peter Aleshire include The Extreme Earth: Mountains (2008, Chelsea House, NY), The Extreme Earth: Deserts (2008, Chelsea House, NY), The Extreme Earth: Undersea Trenches and Ridges (2008, Chelsea House, NY), Arizona Rivers (2007, Arizona Highways), Eye of the Viper (2005, Lyons Press, NY), Cochise: The Last War Won (2001, Wiley Press, NY), Warrior Woman (2001, St. Martin’s Press, NY, and an Italian edition just out), Reaping the Whirlwind (1998, Facts on File, NY) and The Fox and the Whirlwind (1999, Wiley Press, NY).

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