The Twilight and Buffy vampire ecology models were not the first to plumb the mysteries of vampire population dynamics – mathematicians and economists got there first. Mark Strauss has a nice writeup of the wrangling in the vampire literature:
But, this gauntlet had been barely thrown down before it invited a rebuttal from mathematician Dino Sejdinovic. In his article, “Mathematics of the Human Vampire Conflict” (Math Horizons, November 2008) Sejdinovic faults Efthimiou and Gandhi’s logic, since they have not “accounted for the birth-rate of non-vampires and death-rate of vampires (actually the death-death-rate since they are already dead, but when they die again they should stay dead but stop being living) due to close encounters with stakes, garlic and holy water.” Moreover, “vampires are presented exclusively as greedy consumers: a rational strategy of managing their human resources is not considered…”
Their research provoked an outraged response from economist Dennis Snower, who in his article “Macroeconomic Policy and the Optimal Destruction of Vampires” (The Journal of Political Economy, June 1982)…Snower argues that the mortal world can manage its resources in a manner that keeps the undead population in check, while simultaneously promoting long-term economic growth.
Strauss points out that all of these models assume that vampires are the top predator. While the Buffyverse model accounts for Slayer predation, clearly the time is ripe an elucidation of the entire supernatural ecosystem. Zombies and werewolves and demons, oh my.