Dark Banquet (8 page)

Now it was all starting to make sense—why 99 percent of everything that had ever been written about vampire bats dealt solely with the common vampire bat, and why even bat experts had told me that all three vampires would act similarly.
Desmodus rotundus
had been maintained successfully in captivity for nearly sixty years—with some individual specimens surviving for as long as twenty years. Additionally, these bats were numerous across their widespread range and therefore relatively easy to obtain (hence the name “common,” I guess). They were also cheap to feed—as long as you had a ready supply of cow blood on hand. Plus, they were interesting as hell, with a slew of unique behavioral, anatomical, and physiological features.

The other blood-feeding bats,
Diphylla ecaudata,
the hairy-legged vampire (which didn't live in Trinidad), and its white-winged relative,
Diaemus youngi,
were far more rare (relatively speaking) within their limited ranges. They were much more difficult to locate and capture than
Desmodus,
and reports on the difficulty maintaining them in captivity only served to compound the problem.

As a result, most researchers (with a few notable Mexican and South American exceptions) simply avoided working on two of the three vampire bat species. Hence, there were relatively few studies on these bats—especially on topics like comparative anatomy or behavior. Thanks to Farouk Muradali, though, who had graciously decided to let me in on his secret for maintaining
Diaemus
in captivity, the door would soon be wide open for the comparative work I'd proposed to undertake.

Hand feed them until they start guzzling cow blood. How simple,
I thought, until Farouk allowed me to do just that with one of the bats his crew had captured the night before. With no hesitation, I showed off years of animal handling experience by mishandling the syringe and squirting the poor creature with an eyeful of cow blood.

“Must be the gloves,” I said.

Farouk shot me a sideways glance, then smiled. “Yes, that must be it,” he said.

Luckily for the bats, I got better.

“Slaughterhouse Bob” reminded me of Popeye with an extremely selective case of Tourette's syndrome. He was generally a friendly sort of fellow and he seemed genuinely amused that a couple of Cornell types showed up each week at 5 a.m. looking for cow blood. At the first sight of a health inspector, though, Bob's conversation would undergo a seamless transition into a machine-gun barrage of obscenity that would have made the most hardened dockworker blush like a ten-year-old girl. It was an uncomfortable moment for the health inspector as well since the cursing was clearly directed at him. Additionally, while Bob was ranting he was also wielding a nasty device known in the slaughterhouse trade as a captive bolt stunner. This was an instrument that looked like a cross between a power drill and Dirty Harry's .44 Magnum.
^*35

Typically, Kim and I would stand back as Bob herded a single captive cow into the “stunning box,” a heavy-duty, steel-railed enclosure, designed to keep the doomed animal from doing anything more than just standing there. This process generally began right after the health inspector realized that there was somewhere else he needed to be. Stepping up onto the bottom rail of the box, Bob placed the business end of the captive bolt stunner against the cow's skull, at the center of an imaginary X formed by the animal's eyes and the base of its horns. Bob never appeared to rush and he never “chased the cow's head,” taking his time for one clean shot.

The concussive impact of the bolt stunner discharging sounded like a small-caliber pistol firing in an enclosed room (which in some sense is exactly what was happening). The results were as instantaneous as they were stereotypical. The animal collapsed, its brain penetrated by the steel bolt, which had already retracted back into the instrument.

Bob bent down, checking for eye reflexes by touching the cow's cornea. Anything resembling a blink would have meant that the creature hadn't been properly stunned—although in three years of visits to the slaughterhouse we had never seen this happen.
^*36
Having been assured that the enormous bovid wasn't about to right itself, Bob climbed agilely into the stunning box and disappeared behind the cow's hindquarters.

“This here's the most dangerous part of my job,” came a muffled voice from somewhere just south of rump roast. “These cows still got nerves.”

“That's for sure,” I said, finally getting to use the anatomical knowledge I'd accumulated over a long collegiate career.

“One stray kick can break a man's back.”

I pondered that image for a moment. “And that would suck,” I added thoughtfully.

My colleague Kim (an aspiring anatomist herself) nodded in agreement. “Definitely.”

In any event, I always got a bit antsy when Bob jumped in with a brain-bonked cow, and similarly, I always felt relief when Elsie rose from the floor, hind limbs first, cranking toward the ceiling under the power of a motorized block-and-tackle set.

Less than a minute later, the insensate animal had been hung so that its head was suspended above a large plastic barrel. Then, with one expert slice of his knife, Bob would sever one of the cow's jugular veins, stepping out of the way just in time to avoid the powerful torrent of blood that splashed into the blue container.

Once the cow had been fully exsanguinated (and just about the time that Bob started reaching for the “carcass-splitting saw”), Kim and I slid the sloshing barrel of hot blood to the opposite side of the room. Clad in fishing waders and rain gear, our hands were gloved in rubber for reasons that Mr. Playtex couldn't have imagined in his wildest nightmares. Even Bob shook his head in disgust—then he fired up the “Ronko Carcass Master 5000” and began the noisy process of carving Elsie into easy-to-carry pieces.

Standing over the barrel, Kim and I took turns using a metal spaghetti strainer to agitate the blood. By doing so we were actually speeding up the natural clotting process—which had been chemically triggered as soon as the blood left the confines of the severed vein. Although unable to stem the flow of blood from a traumatic wound to a major blood vessel, the hemostatic (clotting) mechanism we were currently stimulating did an extremely efficient job of preventing excess blood loss after minor injuries. For example, a divot-shaped wound of the size inflicted by vampire bats (approximately three millimeters in diameter) would be expected to stop bleeding within one or two minutes. This is not the case, however, in instances in which the wound is created by one of nature's blood-feeding specialists (e.g., leeches and vampire bats). Evolution has provided these creatures with a number of ingredients in their saliva that can interrupt the process of blood clotting for up to several hours. The end result is that the blood feeder is able to drink its fill, having temporarily halted the very same clotting process Kim and I were currently accelerating with our colander.

Vampire bats, feeding at a bite they've inflicted, use their tongues to draw out the blood. Contrary to popular belief, they do not suck blood from their victims. In fact, the physics involved is very similar to what happens when a phlebotomist draws up a patient's blood into a capillary tube. Basically, these thin glass tubes work because their inner diameter is so small that the force of attraction between the blood and the glass is greater than the downward pull of gravity. Thus, the blood pulls itself up the inside of the tube, filling it to a considerable degree.

In the case of vampire bats, the pistonlike motion of the bat's tongue causes blood to flow (via capillary action) along a pair of grooves located on the bottom of the tongue and directly into the bat's mouth. There's even a cleft on the bat's lower lip and a space between its lower incisors to facilitate the blood flow. While feeding in this manner, saliva is constantly applied to the wound.

Vampire bat saliva contains several ingredients that inhibit the body's normal clotting mechanisms. One such anticoagulant compound works by preventing blood platelets from clumping together—an important step in the formation of a plug that will eventually become a blood clot. Meanwhile, another salivary ingredient inhibits the torn blood vessels from constricting—a process that normally reduces blood flow to the wound site and thus from the wound itself. Finally, an enzyme that medical researchers would christen desmokinase (and, later, desmoteplase or DSPA for
Desmodus rotundus
salivary plasminogen activator) breaks down the protein framework upon which the remainder of the blood clot forms.

Primarily because of its antihemostatic properties, vampire bat saliva has drawn considerable attention from the medical community as a potential treatment for certain strokes, namely, those in which a blood clot inhibits blood flow within the brain's blood vessels. In these instances, cells in the region of the brain on the downstream side of the clot are denied oxygen and nutrients. If this blockade continues for long enough, the cells die and the function they were responsible for is impaired. Traditionally, stroke victims have been treated with a compound called tissue plasminogen activator (t-PA). Unfortunately, t-PA must be administered within three hours of the stroke to be effective. After that, the risk of bleeding into the brain increases, and as a result so does brain cell death. Since the average stroke patient waits more than twelve hours before going to the emergency room, t-PA is rarely administered and cannot be considered an effective treatment for the nation's third-largest killer (after heart disease and cancer). Unlike t-PA, though, studies have shown that the vampire bat–derived DSPA (an extremely potent clot buster) can be administered up to nine hours after a stroke has occurred and has no detrimental effects on brain cells.

Since vampire bats often lick the site
before
inflicting their bite, there has also been some speculation that their saliva might contain either a pain-killing agent that prevents their prey from feeling the bite, or an enzyme that could function to soften up the potential bite site. Even without a painkiller or a skin-softening enzyme, the vampire bat's razor-sharp teeth are likely capable of producing a wound that causes little or no pain to the prey.

In what amounts to a strange sort of payback, one modern technique used for vampire bat eradication involves the use of the anticoagulant warfarin. Isolated from a clover mold, warfarin has been marketed for humans since the 1950s as Coumadin. It remains (along with the lung-and intestine-derived compound heparin) a popular blood thinner for millions of patients prone to strokes or blood clots.

Vampire bats treated with warfarin are subject to no such medical benefits. After capturing the bats in mist nets, the animals are painted with a mixture of warfarin and Vaseline and then released so that they can fly back to their roosts. Since vampire bats spend a considerable amount of time grooming one another, the toxic paste is soon spread throughout the members of the roost—with deadly results. Bats soon perish as the ingested warfarin induces massive internal hemorrhaging, causing them to bleed to death.

Although some might consider vampire bats dying from a clot-busting anticoagulant to be poetic justice, others might consider it to be a cruel waste of neat bats. In any event, warfarin paste is certainly several steps up from the days when cries for vampire bat heads sent folks scurrying for dynamite, poison gas, and flamethrowers. As long as vampire bat control personnel are applying the paste to the correct bats, this eradication method is relatively species specific. The drawback is that it's successful only in places (like Trinidad) where individuals are trained to capture the right bat species, untangle them from mist nets (no easy task), and then apply the poisonous paste. All of this must be accomplished without injuring the bat, getting hammered by its powerful jaws, or painting a nonvampire bat by mistake.

A related, but less-cost-efficient, method of vampire control involves the inoculation of livestock with low doses of anticoagulants. Vampires feeding on the inoculated bovine blood suffer the same hemorrhagic fates as those grooming warfarin paste off their roost mates. While this systemic method eliminates the need to capture and correctly identify vampire bats, it does require the treatment of the entire herd in order to be effective.