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By Root 837 0

some of which can be quite gruesome, are the result of aggressive social behavior, thorns, or unsuccessful predation.*25 However wounds are inflicted, they can quickly become beacons for swarms of insects (like screwworm flies) searching for a meal or a warm, moist place to lay their eggs. According to Fenton, insectivorous bats feeding at wound sites may have received additional nourishment from the blood and flesh of the wounded animal itself—and at some point, these protovampires would have switched to feeding solely on blood. Fenton strengthened his case by citing the feeding behavior of oxpeckers, a pair of African bird species (genus Buphagus) related to the omnipresent starlings (family Sturnidae). Oxpeckers glean ectoparasites like ticks off large mammals and they’re also reported to feed at wound sites and festering sores. Similarly, certain finches (Geospiza) remove ticks from giant Galápagos tortoises, which elevate their massive bodies on fully extended limbs to allow the tiny birds total access to the blood-engorged pests.

In any event, my problem with the wound-feeding hypothesis is that it proposes that vampire bats evolved in the face of environmental pressures that would have seemingly acted against the development of such behavior. Not only would potential prey need to be wounded but it would also have to be of conspicuously large size and relatively immobile. Because vertebrate blood is basically made up of water and protein, vampire bats cannot store energy in the manner of non-blood-feeding mammals (as fat, for example). This requires vampire bats to consume approximately 50 percent of their body weight in blood each night. Failing to do so, they can starve to death within two or three days. Now that is an extremely tough way to make a living—and studies have shown that vampire bats (especially young adults) may fail to obtain a blood meal one out of every three nights that they hunt. I estimate that this figure would be prohibitively higher if the prey were required to have existing open wounds. Just as important, there are no living bats (nor mammals, for that matter) that are reported to feed at nonlethal wound sites.

Ultimately, it’s extremely difficult to imagine what would have driven protovampires to abandon an insect-eating lifestyle for one dependent on locating large wounded animals on a nightly basis. I can’t envision the selective pressure that would have led to this behavioral transition. As we’ll see a bit later, the wound-feeding hypothesis also flies in the face of modern vampire bat behavior (sorry about that) since these bats can forage only for short periods of time each night. Finally, echolocation (highly evolved in vampire bats and all of their relatives) would have been useless in differentiating wounded from unwounded prey.

In the frugivore hypothesis, well-developed incisors used to slice through thick fruit rinds would have evolved in fruit-eating protovampires into the bladelike teeth that characterize modern vampire bats. Those who proposed this alternative scenario never discussed how or why this transition from fruit to blood might have occurred and the hypothesis remains undeveloped.

Some critics rejected the frugivore hypothesis on the grounds that vampirism never evolved in the Old World fruit bats*26 even though they too are known to possess large upper incisors. This reasoning is similar to rejecting the wound-feeding hypothesis on the grounds that worldwide distribution of ectoparasites fails to explain why there isn’t a worldwide distribution of vampire bat species. Both of these arguments fall short because they suggest that evolution is somehow completely predictable (i.e., “If vampires evolved from fruit eaters in the New World, they must also have evolved from fruit eaters in the Old World”). In reality, the exact set of circumstances that led to the evolution of blood feeding in New World bats (things like habitats, prey, and predators) was not present for the Old World bats. And even if those circumstances had been present, there would be no guarantee that