Vampire reality check
By Susan Milius
Vampire movies skip the indignities of the all-blood diet. (The endless peeing, the bloating…) Only three mammal species, all bats, have triumphed at vampire living.
Evolving as blood feeders “has changed everything about them: how they move, how they think, what their social life is like,” says Gerald Carter of the University of Maryland in College Park. They’ve even developed a system for sharing blood meals.
One major downside of blood is its high water content. To get sustenance, vampire bats have to swallow a lot of blood and filter out the excess liquid. “Often they’ll be peeing while they’re feeding,” Carter says.