Owls Aren't Wise and Bats Aren't Blind (11 page)

Other North American bats use a mix of CF and FM sounds, very much in the manner described in the jet fighter analogy. These bats are called CF-FM bats. When the longer-range CF sounds of a CF-FM bat, such as the western red bat of Arizona
(Lasiurus blossevillii),
detect potential prey, the bat zeroes in on its target with FM sweeps that give it a much more detailed idea of the prey’s texture.

Because most bat sounds are far above our range of hearing, we fail to realize the extraordinary intensity of their calls. For example, a common species such as the big brown bat
(Eptesicus fuscus)
generates some 110 decibels of sound at a distance of four inches. This is as loud as the alarm on a smoke detector at the same distance; we just can’t hear it! Animals with higher-range hearing than ours, such as domestic dogs and their wild kin, can undoubtedly hear some of the lower-pitched sounds emitted by bats; whether they can hear bat sounds in the upper range of 100 kHz and beyond is highly questionable, however.

To further add to the amazing variety and complexity of bats’ echolocation, consider that some bats which snatch their prey from the ground or from foliage use
low-intensity
sounds that avoid alerting their prey until it’s too late to escape. Such bats, represented by the pallid bat
(Antrozous pallidus),
are said to “whisper.” And as an added complication, even bats of a given species may vary their calls according to local conditions or the prey which they’re hunting.

Considering that a bat’s echolocation can detect the tiniest gnat or distinguish a hard-shelled beetle from a far more succulent moth, it’s absurd to think that it would fly into someone’s hair and entangle itself there. In fact, that’s the last thing that would occur to a bat, which infinitely prefers evasion to entanglement! Perhaps this widely held myth originated with the fact that bats frequently swoop close to people’s heads. However, these bats are merely homing in on insects that are attracted by
their
prey—us. The bats know precisely where they are and what they’re doing, and they have not the slightest intention of lodging in our hair.

It’s the combination of great maneuverability and astonishingly accurate, sensitive echolocation that makes bats in flight so fascinating to watch. Trying to capture the flight of a bat is nearly as difficult as trying to capture the pattern of a swift-flowing stream. Before the eye can register and the brain comprehend the movement, it has already changed like quicksilver. Swerving, darting, swooping, diving, changing directions almost at right angles without warning, a bat’s flight is as unpredictable and indecipherable as the movements of a prestidigitator’s hands. Small wonder, then, that careful observation of bats in flight is such a rewarding pastime.

In addition to older and more superstitious fears, bats are also feared because they’re often portrayed as a major threat of rabies to humans. This, unfortunately, is an enormous exaggeration.

Like most other mammals, bats can and do contract rabies and can transmit it to humans. Nearly always fatal, rabies is a virus disease of the mammalian nervous system. In virtually all cases, rabies is transmitted by a bite from a rabid animal in the last stages of the disease.

Rabid animals in the final stages of the disease exhibit one of two kinds of behavior. In the “dumb” phase of the disease, a rabid animal acts extremely lethargic and may stagger and lose control of its movements. In the so-called “furious” phase, the rabid animal often attacks anything around it, biting living creatures and inanimate objects quite indiscriminately. Animals in this furious phase may also foam at the mouth. This is the behavior that most people think of in connection with a “mad dog.”

At one time it was believed that bats harbored the virus without dying from it. Now scientists have learned that rabid bats do indeed die from the disease. They don’t, however, exhibit the furious phase of the disease and usually don’t attack other creatures. For this reason, anyone who avoids close contact with bats—especially handling them—stands virtually no chance of contracting rabies from them.

Before considering what reasonable precautions one should take to avoid bat rabies, we should first put into perspective what some regard as a great menace. From 1980 to 1996, a total of thirty-six cases of human rabies were diagnosed in the United States. Of these, twenty-one were attributed to bats. This amounts to about 1.3 cases per year of bat-caused human rabies in the United States.

By way of comparison, attacks by non rabid domestic dogs kill as many people in the United States in one year as bat-caused rabies does in a
decade,
and ninety-five people died of bee stings in the United States during the most recent year of reporting. Another way of viewing it is that rabies is now the second-rarest disease in the United States and Canada, trailing only polio in that regard.

From these figures, it’s easy to see that we hardly need to live in terror of rabid bats. Further, having lots of bats around (excluding inside our living quarters) doesn’t appear to increase the chances of acquiring rabies by more than the most minuscule degree. Why? Because hardly any of the cases of bat-caused rabies in humans have been due to our most common bats.

Only two cases of human rabies have been attributed to the big brown bat
(Eptesicus fuscus)
and none to the little brown bat
(Myotis lucifugus)—
two of our most abundant species. In contrast, the solitary silver-haired bat
(Lasionycteris noctivagans)
accounted for fifteen of the twenty-one (71 percent) of the cases of bat-caused rabies in humans.

In spite of these facts, the level of fear about rabid bats sometimes rises almost to hysteria, even among health officials who should know better. The state of New York, for example, is spending a million dollars a year “educating” the public about the dangers of rabid bats in ways that may simply exacerbate the already unreasonable fears which many people have of bats. The basis for this costly and potentially misleading campaign? The state of New York has recorded exactly
one
case of bat-transmitted rabies in its entire history!

As an example of the problems caused by the state’s almost paranoid concern about rabid bats, consider the plight of a prestigious summer camp for boys. Fifty-three boys were sleeping in cabins where a bat was seen flying. Although there was no evidence that the bat was rabid or that anyone had been in contact with the bat, fifty-two of the boys had to receive the very costly rabies vaccination series (the parents of one boy refused the vaccination). At another camp, forty-four campers and counselors were vaccinated, based on health department recommendations,
merely because bats flew over them!

In contrast, Austin, Texas, has made a virtue of its bat population. A million and a half bats have roosted under a bridge in downtown Austin for years, and large numbers of both city residents and tourists regularly gather to watch their nightly exodus, yet not a single person in the area has contracted rabies.

Unfortunately, health officials in a small minority of states (probably no more than a half-dozen) aren’t the only problem. From time to time, various national and regional magazines and newspapers take up the cudgels to verbally beat on bats as a serious threat to spread rabies. A recent short piece in a national magazine is a fine example.

Citing articles in two prominent and highly respected medical journals, the author of this ill-advised piece warned that rabid bats act aggressively “just like raccoons and other infected animals. . . .” As it turns out, the so-called aggressive behavior discussed in the medical journals consisted of such things as bats biting when handled or when a sleeper rolled over onto a bat that had landed on the bed. Implying that rabid bats fly about and aggressively bite people represents a wild extrapolation of the information contained in the medical journals.

The sad part of this near hysteria is that it encourages widespread fear and killing of bats, many species of which are already in serious decline. Solid, scientifically based warnings about handling bats and the proper procedures if one has been in contact with a bat are to be encouraged. Terrifying people about bats in general is quite another matter.

It’s not entirely clear, even to experts, why bat-strain rabies in humans, while extraordinarily rare, is more common than human rabies caused by bites from dogs, cats, raccoons, foxes, and other mammals. However, there is a strong suspicion that people who receive minor bites or scratches from bats may not consider them significant, whereas most people bitten by larger mammals receive rabies shots—unless, of course, the biting animal proves negative for rabies.

Although we have no reason to be apprehensive about the bats that flutter around us at night, some precautions should be followed meticulously.

Never handle a bat, especially one that acts sick, unless absolutely necessary. In
that event, wear leather gloves to protect against bites.
According to the organization Bat Conservation International, “Careless handling is the primary source of rabies exposure from bats.”

Any contact with a bat should be reported to health authorities and your physician.
They will evaluate the contact and decide whether or not rabies shots are needed.

In the event that a person may unknowingly have been exposed to contact with a
bat, this should promptly be reported to your state health department and your
physician, as rabies shots may be warranted.
Examples of this sort of unknowing contact with a bat include such things as a bat in the room of a sleeping person or near a previously unattended child.

If possible, whenever contact with a bat is known or suspected, it’s helpful if the bat can be brought in for rabies testing. Obviously, one should avoid touching the bat; instead, catch it in a net, paper bag, pail, or some other container.

A word about rabies shots might also be helpful. News accounts of rabies and rabid animals occasionally refer to the “painful” series of rabies shots. This view is antiquated, to say the least, and it would be tragic if anyone exposed to rabies avoided treatment for fear of painful shots.

Some years in the past, rabies prevention involved a lengthy series of shots in the abdomen that reputedly were quite painful. Now, however, post-exposure treatment for rabies consists of five shots over a twenty-eight-day period. Although this treatment is expensive, it’s 100 percent effective and isn’t inordinately painful.

My own experience in this regard might be helpful. We generate our own electrical power from the sun, with a backup generator. One day last summer I opened the door of the generator house and was startled when a bat flew out, brushed my arm, and landed on my pants leg.

Afraid that the bat might bite through the cloth if I frightened it, I started to take off my trousers very slowly and carefully. At that point the bat took wing and fluttered to the side of the house, where it clung to the wood. I went inside to get a bag with which to capture the bat, but it was gone by the time I returned.

I then phoned Dr. Robert Johnson, veterinarian for the Vermont Health Department. After reviewing the incident, he determined that, according to the rabies protocol established by the National Institutes of Health, I had not been exposed to rabies. However, during further discussion with Dr. Johnson, I learned about the rabies pre-immunization series.

Pre-immunization consists of a series of three shots over a period of about four weeks (a single booster shot per year is required thereafter to maintain immunity). Unlike the treatment after exposure to rabies, which provides immediate immunity, this series builds a person’s immunity gradually.

I felt that this treatment was well worthwhile and went ahead with it. Each shot cost me only thirty-five dollars at a local health clinic, and I can testify to the painlessness of it; I literally didn’t even feel one of the shots, and the other two were no more than tiny pin pricks. There was no soreness in my arm later, either. So much for the notion that modern rabies shots are extremely painful!

Occasionally a bat will, by some means or another, enter a home and fly about. Usually utter panic ensues, with frantic efforts to kill the creature. This is precisely the wrong reaction! Clearly, it isn’t desirable to have bats in one’s home, any more than mice, squirrels, and assorted other little beasties belong in our living room, bedroom, or kitchen—but there’s a better and more effective way than trying to demolish the bat. In most such cases, the bat is a young one setting out on its own. It’s confused, and would be just as happy to leave as the human occupants would be to see it depart. In this situation, if doors and windows are opened, the bat will usually find its own way out in a very short time.

Bats may also inhabit parts of a building outside our living quarters. It’s beyond the scope of this book to list all the many ways of keeping bats from roosting in an attic, under the eaves, or in other places where they might not be wanted. Your state wildlife or natural resource agency, or an organization such as Bat Conservation International, can provide that sort of detailed information.

So far, I’ve tried only to demolish some of the myths, superstitions, and gross exaggerations that have been attached to bats over many centuries. Now it’s time to move on and view the bat in a very different light.

The truth is that bats are enormously beneficial, especially in controlling insects. One bat can eat several thousand insects in a single night, and the 20 million Mexican free-tailed bats that roost in Bracken Cave, Texas, consume an estimated one-quarter to one-half million pounds of insects each night! Some North American bats, and a number of tropical species, are also invaluable as plant pollinators.

In fact, it’s difficult to overestimate the role of bats in controlling a wide variety of insects, many of them harmful—or at least unpleasant—to humans. A single little brown bat can devour up to
twelve hundred
mosquito-sized insects in an evening. Imagine what it might be like around our homes if these industrious little insect traps weren’t patrolling our surroundings night after night, snapping up mosquitoes, gnats, and other biting insects! Small wonder, then, that many people have chosen to erect bat houses near their homes to encourage a greater population of bats.