The other day, over breakfast, my first-grader asked how long it would take a vampire bat to drain a pig. I, of course, had no idea. Fortunately, we live in an Age of Wonders:
A quick trip to Wikipedia informed me that “A typical female vampire bat weighs 40 grams and can consume over 20 grams (1 fluid ounce) of blood in a 20-minute feed.” From prior experience buying live hogs and arranging for their slaughter and processing (don’t ask), I knew that there were something like 10 or 12 pounds of blood in a pig. A quick Google confirmed that it averaged around 9.5 pounds of extractable blood, which is conveniently roughly 9.5 pints, or 152 fluid ounces.
So, if she could feed nonstop (which she can’t), then a vampire bat could exsanguinate a very calm pig in roughly 50 hours. Alternately, a single bat could feed off a single pig for 152 days (at one fluid once per day) before the little fella was bone dry. *But*, I told him, we need to keep in mind that 1 fl. oz. is a very small amount of blood, and that the body regenerates blood regularly. People regularly give a pint, and it doesn’t seem to take more than a week for them to bounce back. Sorry, buddy, but I don’t think the little bat would *ever* drain the pig.
*Booom!* Question answered!
Kinda.
Because not knowing that blood replenishment rate was bugging me, so I started Googling again, and *holy crap!*, it takes a lot longer than I thought to make back that pint you gave the Red Cross! I’m not sure how fast pigs replace blood, but humans do so at around three fluid ounces per week–which is a bit under half an ounce per day an average. So, if the bat hit the same average pig for a fluid ounce each night, the pig would make half of that back the next day (in theory), meaning that to actually exsanguinate a live pig, the vampire bat would have to invest most of a year.
*But* how much blood can a pig loose before he keels over? Or before the body’s built-in replenishment system goes off the rails? I haven’t the *foggiest*–although life experience tells me that a human can lose *more than half her blood volume* and still be perfectly functional (albeit kinda logy, and certainly pale). So how long could a healthy pig go if it was being plagued nightly by a vampire bat? Clearly more than half a year. Maybe three quarters? At what time does that bat use its sharp lil teeth to carve “SOME PIG” into the wall of the barn?
Anyway, in the end, this seemed like an *excellent* teachable moment:
Remember, kids, given a persistent spirit and enough time, even the humblest vampire bat can completely drain the mightiest swine.
Why there is no children’s book with this as its central motif is, frankly, a stumper to me.
At any rate, the day after that momentary diversion on our way to the grave, I came across this, and it just sorta seemed like I *had* to share it. So I am.
(thx to these friendly Twitterati for checking my blood math: @hypomodern, @logista, @vaguery, and @dgoings!!!)
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