Monday, December 08, 2008

To them, we are warm, walking fuel tanks

kw: book reviews, nonfiction, animals, feeding habits

A word of caution: much of the book is not suitable for reading while you have your morning cereal. Sensitive souls may be subject to attacks of the heebie-jeebies.

Behold the visage of the Common Vampire Bat, by far the most common of the three bat species that consume only blood. Of more than 1,000 species, more than 2/3 eat only insects and most of the rest eat only fruit. Just three species consume blood, and they are among the smaller bats, weighing about two ounces (60 g).

Stories and natural history notes about vampire bats occupy the opening chapters of Dark Banquet: Blood and the Curious Lives of Blood-Feeding Creatures by Bill Schutt. Graphics by Patricia J. Wynne complement the text. Once thought to be very similar, the three species are shown to be quite different. Whereas the Common Vampire Bat responds to handling by fighting and biting, the author reports that he has never been bitten by a White-Winged Vampire Bat. The Common species is the ground-walking species, the one that looks like a little creeping Dracula, complete with cape, when it walks over to a sleeping chicken or pig to commence feeding. Thus it is much more robust, and can leap almost a meter into the air if startled. The other species seldom walk on the ground, cannot leap, and usually attack birds in trees (feeding on their toes); so the latter are much less robust.

But the narrative is just getting going when the author bids farewell to bats and turns his attention to other blood feeders. The middle section of the book begins with a survey of vertebrate blood and the vertebrate blood system, and some comparisons to the hemolymph systems of arthropods (emphasizing lobsters over flies). He discusses the strange practice of bloodletting as practiced by doctors for two millennia (trivia question: what does the red stripe on a barber pole signify?) Then the narrative turns to leeches.

In one area leeches and vampire bats are similar: both have anti-clotting saliva, so that the victim loses much more blood after the feeder finishes, up to ten times. A chicken that has just "donated" an ounce of blood to a vampire bat may lose another five to ten ounces before the wound begins to heal. Chickens are big birds, but that's a lot of blood and not all survive the encounter.

Leeches are much easier to handle and maintain than bats, so when it is necessary to extract blood, they are still used medicinally. They are essential for certain kinds of surgery, such as reattachments, for which the enhanced blood flow they promote can ensure success. Leeches do have to be watched, however. There is at least one case of one creeping into the wound it was placed next to…you really don't want one of these left inside your body!

The book closes with shorter treatments of a variety of creepy "bugs", including bed bugs, ticks, and chiggers, and a short chapter on the candiru, a South American catfish the size of a small, narrow pencil. There is only one documented case of one "attacking" a urinating man and getting in where the sun won't shine, but one case (plus tons of folklore) is enough to make them a bit less popular than Piranhas.

There is no section on mosquitos, the blood-sucker with which suburban North Americans are most familiar. But they are mentioned here and there, throughout, including one note that someone dies of a mosquito-borne illness, usually malaria, every twelve seconds. The diseases "vectored" by blood-feeding animals is a giant subject in itself. About half of all entomologists worldwide are employed in public health related to diseases carried by blood-feeding insects. One-tenth of all childhood deaths, worldwide, are from malaria, and another tenth—or more—by other diseases primarily carried by biting insects.

A fascinating book. And, while I did read some of it over my breakfast, there was a time or two that I set it aside for reading later.

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