From the author's note in a recent vampire novel, I discovered a book that would be fascinating and valuable to all writers who create vampires as well as anybody interested in the often "alien" weirdness of animal biology and behavior in our terrestrial ecosystems. DARK BANQUET (2008), by bat expert Bill Schutt, subtitled "Blood and the Curious Lives of Blood-Feeding Creatures," surveys the "obligate sanguivores" (creatures that feed exclusively on blood) of the animal kingdom. The animals discussed range from vampire bats (the only mammal in this category) to leeches, bedbugs, ticks, etc., with glances at a few creatures that sometimes consume blood but don't live on it, such as "vampire finches." Anticoagulants and anesthetics in the saliva of vampire bats and leeches have inspired similar features of the naturally evolved vampire species in my own fiction. It's intriguing that, because of the high volume of water to nutrients (mainly protein) in blood, vampire bats have to ingest a large percentage of their body weight every day, yet leeches and bedbugs can go for weeks or months without feeding. What makes the difference—the metabolic rate of mammals versus invertebrates? If so, my own vampires' ability to survive in a dormant state, without nourishment, theoretically forever must be a bit of a hand-wave, but after all, it's fiction. I've also postulated that my vampires' saliva has antiseptic properties that keep the bite wounds from getting infected; the saliva of human beings and some other animals does contain antibacterial chemicals, but this book doesn't mention any such qualities in bats or leeches.
One vampire bat trait I definitely did not adopt for my fictional species is the need to get rid of excess water to make themselves light enough to fly away after drinking from a victim. The bats often start urinating even while they're still feeding. Far from glamorous!
After the opening chapter on vampire bats, enlivened (like the rest of the book) with personal anecdotes and observations, Schutt devotes a section to the physiology and chemistry of blood in the context of the history of medical science. One topic I wish he'd covered more thoroughly, instead of briefly mentioning, is the nutritional content of blood and the digestive adaptations needed for an animal to survive on what his final chapter labels "A Tough Way to Make a Living." I've often wondered how many calories are in a pint of blood and have never been able to find a definitive answer.
For me, the most fascinating tidbit of information in the book is that vampire bats have been observed to snuggle up to the brood patches on hens' chests. The hen relaxes, contentedly settling down as if the predator is a chick, and allows the bat to feed. On other occasions, a hen may respond to a bat on her back by passively assuming the mating posture, as if mounted by a rooster. So my premise that members of my vampire species lull or seduce human victims into willingly surrendering their lifeblood has a factual basis in biology!
Margaret L. CarterCarter's Crypt