Dark Banquet (4 page)

Birds have evolved a solution to this problem since both their downstroke and upstroke muscles are located
below
the wing. Situated on the sternum (deep to the bird's downstroke-driving pectoral muscles), the supracoracoideus muscle sends its long tendon snaking through a hole in the shoulder joint to an attachment site on the humerus. When the supracoracoideus muscle contracts, its tendon acts like a pulley to raise the wing. The end result is a smoother (less jerky) flight in birds compared to bats.

These performance differences follow a general trend in most flight characteristics in which birds are more aerodynamically efficient than bats. This is almost certainly because birds have been flying (and, in the case of hummingbirds, hovering and feeding on nectar) far longer than their mammalian counterparts.

Back at Wallerfield, Farouk nodded at my tiny captive. “You should release that
Glossophaga
before we leave,” he said. “If you want it to live.”

“Why's that?” Janet asked. We'd been bagging bats in Trinidad for several weeks, then taking them back to the PAX Guest House where we were staying in Tunapuna.
^†9

“Glossophaga
has a very high metabolic rate,” Farouk replied. “If that one doesn't get nectar tonight, it will starve to death.”

“Yikes,” I said, glancing down at the bat with renewed interest.

Janet nudged my arm. “Sounds like those shrews we caught with Deedra and Darrin last year at Arnot Forest.”

Janet had nailed it. Shrews are tiny, insectivorous bundles of energy. Superficially, they resemble rodents (another example of convergent evolution), but they have amped-up, nutrient-burning bodies, that, like the nectar-feeding bats, require a constant and relatively immense intake of energy. The shrews we'd taken during a mammal survey in a forest near Cornell had a resting heart rate of approximately eight hundred beats per minute, and when pressed, they could reach fifteen hundred beats per minute—the highest ever recorded for a mammal. As a consequence, shrews have to eat almost constantly—worms and insects, mostly—but sometimes even other shrews. Their aggressive demeanor and toxic bites also enable them to tackle animals much larger than themselves. During one of our long nights in the field, I'd brought up the topic of a creature feature I recalled seeing as a kid. It was the unintentionally funny, 1959 horror flick,
The Killer Shrews,
in which dogs outfitted with goofy shrew wigs, terrorized a handful of cocktail-guzzling scientists, a well-endowed young woman, and a testosterone-squirting hero in a captain's cap. Besides a last line that rivaled Clark Gable's in
Gone with the Wind,
what I found most memorable about this mostly forgotten cinema “classic” was the fact that the filmmakers had gotten at least one thing right (two, actually, if you count the alcohol intake by the scientists). If indeed shrews
had
evolved or, in this case, mutated, to be the size of dogs (even small dogs)—humans would have had a
serious
and unbelievably vicious predator to contend with. Luckily for those of us collecting real shrews, there was no danger—only the discomfort of late nights during which we had to check over a hundred “live traps” every two hours—to prevent our hyperactive captives from starving to death.

In the icehouse at Wallerfield, Janet and I took a last look at the amazing little pollinator.

“See ya,” I said, gently flipping the bat upward.

The tiny creature disappeared in a whisper of parchment.

I looked over at Farouk, who nodded and motioned toward the stairwell. “We'd better get going, Bill. We don't want to be out here after dark.”

“Second that,” Janet said.

I turned to say something to my wife, but she was already moving toward the exit.

“Right,” I said, following the beam from Janet's headlamp as she sought the comfort of sunlight.

Like nectarivory, blood feeding in bats is another highly specialized lifestyle, but there is little or no convergence between birds and bats, in all likelihood because there's no competition between the two groups. While there are birds that regularly feed on blood (e.g., vampire finches and, indirectly, those that pick ectoparasites like ticks off of large mammals), none of these birds is an obligate blood feeder like the vampire bats. In other words, no bird species will starve to death in two or three days if it doesn't secure a blood meal. This means that as far as
vertebrate
sanguivores are concerned, bats hold the exclusive rights to their aerial and terrestrial niches.
^*10

So what did the early naturalists have to say about vampire bats, and how did these creatures become forever tied to the growing vampire hysteria that was simultaneously taking place in Europe? How did blood feeding evolve in bats, and why has it never appeared in birds—an older and more diverse group? Oh, and finally, why is just about everything people
think
they know about vampire bats completely wrong?

It might be best to start with this last question.

Can you tell me why in the Pampas, ay and elsewhere, there are bats that come out at night and open veins of cattle and horses and suck dry their veins; how in some islands of the Western seas there are bats which hang on the trees all day, that those who have seen describe as giant nuts or pods, and that when the sailors sleep on the deck, because that it is hot, flit down on them—and then in the morning are found dead men, white as even Miss Lucy was?

—Bram Stoker

2.

CHILDREN OF THE NIGHT

W
hen the explorers of the New World returned home to Europe in the fifteenth and sixteenth centuries, they were far more concerned with gold, God, and geography than they were with accurate zoological accounts. Amid fanciful tales of sea serpents, giants, and mermaids, there were also reports of bats that fed at night upon the blood of unfortunate humans and their livestock. Although these creatures were generally described as being hideous, with wingspans of up to five feet, nobody actually took the time to figure out which bats were vampires and which weren't. The rule of thumb seemed to be that the largest and ugliest bats were vampires—and, on both accounts, the explorers were dead wrong.

Early taxonomists contributed significantly to the confusion. Carl von Linné (who actually Latinized his own name) and the morphologist Étienne Geoffroy Saint-Hilaire were responsible for initiating a misunderstanding regarding bats and blood feeding that still exists today. With little knowledge of the bat's biology and no regard for their actual diet, they assigned scientific names like
Vampyrum spectrum
(which happens to be a
really
large bat),
Vespertilio vampyrus, Vampyressa,
and
Haematonycteris
to bats that had never so much as snuck a sip of blood.
^*11

Even card-carrying tropical zoologists got things horribly wrong. Johann Baptiste von Spix, curator of the zoology collection at the Bavarian Academy of Sciences, had spent nearly three years on a collecting trip to Brazil starting in 1817. He returned with thousands of specimens, many never before seen in Europe. One of these was
Glossophaga soricina
(the pollen-dusted bat I had “swoop-netted” at Wallerfield). Spix described
Glossophaga
as “a very cruel blood-sucker”
(sanguisuga crudelissima),
hypothesizing that the creature we now know to be a delicate hummingbird mimic actually used its brushlike tongue tip to reopen the wounds it had somehow inflicted with its tiny teeth.

The chiropteran disinformation campaign continued well into the nineteenth century. By this time collectors were swarming all over the Neotropics in an effort to supply the burgeoning museums and private collections of Europe. Even though naturalists like Charles-Marie de La Condamine and Alfred R. Wallace had begun writing more factual accounts of vampire bat attacks, these creatures were still considered to be mythical by many in the European scientific community. The problem was that while the slaughterhouse results of a nighttime vampire bat attack were easy enough to record, identifying the actual bat that left the mess was more of a poser. And, as it turned out, even when the culprit was correctly identified, prejudice got in the way.

In 1801, in Paraguay, the Spanish cartographer and naturalist Felix D'Azara collected the creature that would eventually become known as the common vampire bat. But even though D'Azara asserted that this was the bat responsible for attacks on humans and livestock, British and French taxonomists thumbed their noses at his claim. In 1810 the same bat was named and described by Geoffroy.
Desmodus
(literally, “fused tooth”) was named for its unique incisors: a chisel-shaped set of uppers and a uniquely bi-lobed pair of lowers. Unfortunately, there was absolutely no mention of blood feeding in Geoffroy's description of
Desmodus.
Similarly, in 1823 Spix named and described a bat that had been collected in Brazil, but it would be years before
Diphylla ecaudata
would be recognized as a second vampire bat species.
^*12

It wasn't until 1832, when Charles Darwin and his servant observed
Desmodus rotundus
feeding on a horse, that the English-speaking world had a name to associate with the blood-feeding deed.

The vampire bat is often the cause of much trouble by biting the horses on their whithers. The injury is generally not much owing to the loss of blood as to the inflammation which the pressure of the saddle afterwards produces. The whole circumstance has lately been doubted in England; I was therefore fortunate in being present when one was actually caught on a horse's back. We were bivouacking late one evening near Coquimbo, in Chile, when my servant, noticing that one of the horses was very restive, went to see what was the matter, and, fancying he could detect something, suddenly put his hands on the beast's whithers, and secured the vampire.
^*13

(Charles R. Darwin)

Because of similarities in appearance, behavior, and range (parts of Mexico, the warmer regions of South and Middle America, plus the islands of Trinidad and Margarita),
Desmodus, Diaemus,
and
Diphylla
were initially placed into their own family, the Desmodontidae. More recently, researchers have reduced them to a subfamily within the large, primarily Neotropical family Phyllostomidae. There are around one hundred and fifty phyllostomids (i.e., members of the family Phyllostomidae) and they're sometimes referred to as New World leaf-nosed bats. This is because they live in the Americas and most of them have a vertically projecting, spear-shaped nasal structure. Although nose leaves may look menacing, they are actually soft and pliable.

Early naturalists claimed that nose leaves were used by vampire bats as deadly flesh stilettos, to gouge victims before a blood meal. Many years later, scientists studying the strange ultrasonic capabilities of bats uncovered an interesting, though decidedly less gory function for the nasal protuberances. Just as a megaphone can be used to direct the human voice, the nose leaf is actually involved in directing the echolocation calls emitted by the bat. Ironically, nose leaves are greatly reduced in size in vampire bats (like
Desmodus
) where they function primarily in thermoperception—the ability to sense differences in temperature. This is an adaptation that comes in handy as vampire bats approach their warm-blooded prey in complete darkness. Once the bat gets within around fifteen centimeters of its target, thermoreceptors in the low, ridgelike nose leaf can detect the slight temperature differences that exist in areas of the skin where blood vessels lie just below the surface. The bat uses this information to help determine where a bite will be made.
^*14

In hindsight, the function of the bat nose leaf was one more bit of misinterpreted information for early naturalists, who used the presence of this structure to mistakenly categorize over a hundred species of non-blood-feeding bats (e.g.,
Glossophaga
) as vampires. Along these lines, it should also be noted that nose leaves occur in two additional (and only distantly related) families of Old World bats, the Rhinolophidae and the Megadermatidae (the latter is now commonly known as false vampire bats). This is yet another example of convergent evolution, and although neither of these groups have any blood-feeding members, the presence of a nose leaf probably contributed to claims of vampire bats inhabiting Europe, Africa, Southeast Asia, and the Indo-Pacific.
^†15

Even though the identity of the three vampire bats was not fully known until the 1890s, bloodletting bats have been referred to as vampires since the mid-1700s, and although vampire folklore did not begin with the discovery of vampire bats, it was clearly strengthened by it.

According to folklorist Stu Burns, the word
vampire
has its somewhat hazy roots in the Slavic proper name
Upir,
first recorded in an eleventh-century Russian manuscript.
Vampire
(or
vampyre
—used hereafter to denote the mythical bloodsucker) is a westernization of
Upir
(or
Upyr
) and the word appears to have been coined in English in a pair of 1732 publications.
Vampyre
refers to a corpse that has returned from the dead to drink the blood of the living. Similar creatures were said to haunt the rural villages of nearly every Slavic nation. Not surprisingly, each culture gave their monster its own name (e.g.,
vukodlak
in Serbia,
strigoii
in Romania,
eretika
in Russia,
insurance salesman
in…well, never mind). It should also be noted that stories of vampyrelike creatures have a worldwide distribution. Bloodsuckers inhabit the folklore and literature of ancient China, Babylonia, and Greece, as well as the pre-Columbian cultures of Mesoamerica (most notably as the Mayan bat god Zotz or Camazotz).

Vampyre hysteria ebbed and flowed throughout Europe in the fifteenth and sixteenth centuries, reaching its peak in the 1730s. At this time it became quite popular to dig up dead bodies, accuse them of crimes, and then smash a stake through their decaying hearts. According to legend, those corpses hoping to avoid skewering often chose to transform themselves into something not quite so corpselike. Although Slavic vampyres never actually took the form of bats, popular transformation destinations included animals or inanimate objects such as fire and smoke. Fear was an important component of most vampyre legends, but some of these creatures would have had a hard time striking terror into your average toddler. For example, Muslim gypsies in the Balkans won't keep pumpkins or watermelons for more than ten days (or after Christmas) for fear that they'll transform into vampyres. Thankfully, these vampyre veggies have no teeth—so they're reduced to pestering people by rolling around the ground, growling, and dripping blood.