Dark Banquet - Bill Schutt [26]
Unlike Desmodus, Diaemus youngi (which resembles a winged teddy bear) has contributed little if anything to vampyre folklore. Perhaps they were once fast and aggressive, and maybe they even initiated flight similarly to their spring-loaded cousins. But now their movements are more deliberately paced and show little sense of urgency. When placed on the surface of our force platform, white-winged vampires would give a little hop or two, then scuttle off to find a dark corner in which to hide.
Watching Diaemus feed arboreally, we saw why they didn’t need to catapult themselves into the air. Approaching a roosting bird from below the branch, white-winged vampires moved slowly and stealthily—advancing one limb at a time—and always keeping the branch between itself and the underside of its intended prey. Once situated beneath the feathered lunch wagon, Diaemus picked a potential bite site, usually on the bird’s backward-pointing big toe (i.e., the hallux). This made perfect sense, since feeding from this particular digit kept the bat better hidden from above than if it had chosen to feed on one of the three forward-facing toes. After licking the chosen site for several minutes, an apparently painless bite was inflicted using the razor-sharp teeth that characterize all three vampire bat species. The bite was never violent and very often occurred as the bird shifted position slightly on its perch, as if reacting to some slightly uncomfortable irritant. Still hanging below its completely oblivious prey, Diaemus began feeding, and within five minutes it began peeing. It did so by extending one hind limb sideways and downward, deftly avoiding the embarrassment of soiling itself while eating. After feeding for between fifteen and twenty minutes, the bat would release its thumbs from a branch, hang briefly by its hind limbs, then drop into flight. Initiating flight in this manner, there was absolutely no need for Diaemus to jump, and so it didn’t, at least not into flight.
On numerous occasions, we did observe Diaemus feeding on birds from the ground. Supporting its body in a low crouch (as compared with the extreme upright stance of Desmodus), the white-winged vampire was quite adept at hopping around (rather comically) in pursuit of a feathered blood meal. This behavior had not been reported in the wild and we used it to propose that the white-winged vampire bat had made a relatively recent return to the trees, thus avoiding competition with its ground-feeding cousin, Desmodus.
During these terrestrial feeding bouts we occasionally recorded behavior that approached chick mimicry on the “weird-o-meter.” This occurred after the bat leaped or climbed onto the chicken’s back, then scuttled forward, intent on biting the back of the bird’s head or its fleshy comb. Male chickens mounted in this fashion quickly grew agitated and dislodged the bat with a shake and a peck. Hens, however, had an entirely different response. Rather than showing annoyance, female chickens quickly assumed a crouching posture that they maintained until after the vampire bat had finished feeding and hopped off. With a little research into poultry behavior, we learned that this was the identical posture taken by a hen while being mounted by a male bird—for a completely different reason.
Another way that Diaemus differs from Desmodus and Diphylla is by the presence of a pair of cup-shaped oral glands located at the rear of the mouth. When Diaemus gets upset (or, as we observed, during dominance hierarchy behavior), the glands are projected forward and they can be seen quite easily when the bat opens its mouth. As it does, Diaemus produces a strange hissing