The problem wasn’t so much a lack of prey as a lack of difference from it; vampires were such a recent split from the ancestral baseline that the reproductive rates hadn’t diverged. This was no woodland-variety lynx-hare dynamic, where prey outnumbered predators a hundred to one. Vampires fed on things that bred barely faster than they did. They would have wiped out their own food supply in no time if they hadn’t learned how to ease off on the throttle.
