What did giant extinct vampire bats eat?

What did giant extinct vampire bats eat?

Macrauchenia having a really bad day in the Pleistocene. This scene >>is a parody and almost certainly never happened<<. Tet Zoo dollars to whomever recognises the obvious derivation. Illustration by Darren Naish.

Prior to the spread of people and domestic livestock, vampire bats (here we’re mostly talking about the Common vampire Desmodus rotundus) most likely fed on capybaras, tapirs, peccaries, deer and birds, though we know that they also sometimes feed on fruit bats and reptiles. Populations that live on islands off the Peruvian and Chilean coasts feed on seabirds and sealions. Now that the Americas are full of millions of cattle, horses, donkeys, pigs and chickens however, vampires have largely switched to these domestic prey, and it’s said that the majority of modern vampires now feed almost entirely on the blood of livestock, particularly cattle, horses and donkeys. [Image of vampire skeleton below by Mokele.]

Skull of Desmodus rotundus, showing amazing dentition. Image by Mokele, licensed under Creative Commons Attribution 3.0 Unported license.

There are three extant vampires. We know from fossils that two of them (the Common vampire and Hairy-legged vampire Diphylla ecaudata) were extant in the Pleistocene, and members of the same lineage as the third species (the White-winged vampire Diaemus youngi) must have been present too, since phylogenetic studies show that Diaemus is as old as Desmodus (Honeycutt et al. 1981, Wetterer et al. 2000, Jones et al. 2002).
But it gets better: there are numerous additional fossil vampires. They include Desmodus archaeodaptes from the Upper Pliocene of Florida (this is the oldest reported vampire species), De. stocki from the USA and Mexico, the Cuban endemic form De. puntajudensis, De. draculae from Venezuela, Belize and Brazil, and an unnamed related form from Buenos Aires, Argentina. De. stocki – sometimes known as Stock’s vampire – was 15-20% bigger than the extant Common vampire. Indeed, a specimen now included within this species was originally named De. magnus. De. draculae – sometimes referred to as a ‘giant vampire’ – was about 25% bigger than a modern Common vampire, suggesting a wingspan of perhaps 50 cm and a mass of about 60 g. This makes it on par with a large horseshoe bat or small fruit bat: keep in mind that the majority of ‘microbats’ weigh between 10 and 20 g!
What sort of animals were these fossil vampires feeding from? Of the living vampires, both the Hairy-legged vampire and White-winged vampire mostly prey on birds. However, the Common vampire mostly preys on mammals, and because the fossil species are all members of the genus Desmodus, it’s reasonable to assume that they, also, mostly fed on mammals. However, they surely exploited other prey when they were available. Here’s a wholly speculative reconstruction of a Pleistocene Desmodus feeding from the leg of a sleeping teratorn (aka teratornithid). Teratorns are giant, condor-like birds; the last time I used a version of this image I was reminded that they likely defecated down their legs as living New World vultures do today. Nevertheless, I’m sure the bat is safe in this particular instance…

Pleistocene Desmodus feeds from sleeping teratorn. Image by Darren Naish.

A few vampire bat fossils are preserved in association with large mammals. A fossil Common vampire from a Brazilian cave, radiometrically dated to about 12,000 years ago, was discovered adhering to the underside of a coprolite produced by the sloth Nothrotherium (Czaplewski & Cartelle 1998) and De. stocki fossils from Florida are preserved in the same caves as ground sloths. A skull belonging to De. draculae was preserved in association with a skull of the extinct horse Equus neogeus. None of these associations demonstrate the predatory preference of the extinct vampire species, but they are at the very least highly suggestive. The idea that some of these bats may have fed on giant sloths is likely and entirely acceptable, and one published life restoration – a drawing by Randy Babb, in Brown (1994) – depicts a De. stocki feeding on a nothrotheriid sloth.

An extinct Pleistocene vampire (probably Desmodus stocki) feeding from a giant sloth. Illustration by Randy Babb, from Brown (1994).

Intriguingly, the morphology of some of these vampires suggests that they differed in ecology and behaviour from the living vampire species. Both De. archaeodaptes and the Cuban species De. puntajudensis seems to have had far more freedom of movement in their jaw joint that the Common vampire, a feature suggesting that they somehow differed in how they procured and/or bit their prey (Morgan 1991, Suarez 2005). The robust hindlimb bones of De. puntajudensis and De. stocki also suggest that their style of terrestrial locomotion differed from that of the Common vampire, though exactly how it differed remains unknown. The large size of De. stocki, De. draculae and the Argentinean giant form of course indicate that they fed on larger prey than living vampires and, as noted, these fossil bats are sometimes found associated with ground sloths.

Bats have been covered on Tet Zoo quite a bit: there’s lots in the archives on vampires and vespertilionids in particular. However, there is still tons and tons to get through!