Keeping Track Of 'Leptonycteris sanborni'.
By Kevin Franklin
WHEN THEY START emerging, try not to move around a lot or make much noise," counsels Yar Petryszyn, University of Arizona curator of mammals.
I find a reasonably comfortable slab on the tailings pile in front of the abandoned mine and wait. A steel mesh drapes over the black maw of the mine shaft and members of our group mill about carrying strange-looking scientific equipment.
We wait for the emergence of the three-inch Sanborn's long-nosed bat, Leptonycteris sanborni. Petryszyn is working with several biologists and numerous volunteers to get a handle on the population and natural history of the endangered migratory bats, which have only recently made their annual arrival to this mine in the Sierra Vista area. (The mesh is there year-round to keep idiots from killing themselves). This will be the fourth year Petryszyn has counted the transient population, and each year their number has dropped; from an initial 18,000 bats to roughly half that number last year.
The reason for the decline is a mystery. During most of the year the bats are in Mexico and no one is entirely sure of their movements. Even in the United States, the whereabouts of all their roosts are unknown, as is whether the total number of bats is dropping or if they're simply making use of different sites.
As dusk falls, a few insect-feeding bats emerge and disappear; but the fruit and nectar eating long-nose wait for twilight to pass. At many bat roosts raptors and owls wait for the bats, nabbing several quick meals in the process. By waiting for nightfall the long-nose bats avoid most raptors, though owls have no problem with darkness. And neither do bobcats.
Petryszyn knows of a roost in Mexico where a female bobcat waits above the entrance to a long-nose bat cave and swats her dinner out of the sky. He's counted dozens of bat wings and parts on the cat's perch--though with a colony of 40,000 a few lost members has minimal impact. One of the researchers even found a rattlesnake seemingly poised to strike a bat out of the air during an emergence, but never saw the snake take a bat.
At this particular mine there are no predators, only a few biologists, graduate students and bat junkies. Natural predators cause no long-term damage to bat populations. Humans, on the other hand pose a serious threat to the species. While the sheer number of long-nosed bats seems large, they concentrate in only a few mines and caves. A single yahoo with a penchant for killing could destroy a substantial portion of the entire population at a single cave. For this reason, the exact locations of bat caves are closely guarded secrets.
When the last tinges of twilight have faded there's a stirring in the mine. I can hear the flap of thousands of leathery wings. At first, nothing visible is happening, just that strange otherworldly sound of thousands and thousands of bats stretching and warming up their wings in preparation for flight. Then a few bats swoop out of the dark, stony entrance--and then back in again. Slowly the activity of the scout bats increases. Then, like the light patter of drops before a thunderstorm, a few bats take off into the night. A few seconds later, a torrent erupts from the old mine. The strong smell of guano is dragged out like a foul tide.
As the furry flight continues, of bats race overhead and thousands fill the sky. In the remaining dim light I see them aiming directly at me and then, seemingly at the last possible moment, veer off like wild teenagers playing chicken.
Later, Petryszyn and the other biologists estimate 17,000 bats were in the cave. The population for this location seems to have rebounded. Where the other bats have been going for the past couple of years, no one knows.
At the moment, it seems like millions of bats are in the air. I feel a fine mist and realize the bats are doing what most folks do at the beginning of their day. Though my fascination with the whole experience stays dead on, I don't mind stepping aside a pace and under cover.
I amble over to Homer Hansen, an environmental soil scientist, budding biologist and general bat groupie. He's taking advantage of the last vestiges of daylight to see the silhouette of the bats against the horizon.
"This," Hansen says "is one of the great natural wonders of the world, right alongside the aurora borealis or swimming with whales."
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