Only a handful of the world's vampires are vertebrates
Stephen Dalton/Science Source
Halloween horror aside, vampires are really pretty spineless.
Most have no backbone at all. By one count, some 14,000 kinds of arthropods, including ticks and mosquitoes, are blood feeders. Yet very few vertebrates are clear-cut, all-blood specialists: just some fishes and three bats. Why hasn’t evolution produced more vertebrate vampires?
The question intrigues herpetologist Harry Greene of Cornell University, who “can’t think of a single example among amphibians and reptiles,” he says. (Some birds are opportunists, sneaks or outright meat eaters, but they don’t have the extreme specialization of bats.)
Kurt Schwenk of the University of Connecticut in Storrs, who studies feeding morphology, comes up empty, as well. As he muses over what animals might have precursor biology that could lead to blood feeding, “a leechlike or lamprey-like blood-sucking tadpole