Bat blunders

Abstract

The only real mistake is the one from which we learn nothing. It's my guess that when industrialist Henry Ford (he of the Model T) wrote these words he was probably thinking about learning from one's own slip-ups. But we can also learn from other people's mistakes, and the greater their errors, the greater, perhaps, the knowledge we can reap. So hang on tight, for we are going back 200 years to a loft in an abandoned house (in what is modern-day Guyana), a once-fine dwelling now long into the process of repossession by Nature, where Charles Waterton, one of the greatest naturalists of his time, got into a huge vampire bat muddle! In his immensely popular book Wanderings in South America (London: J Mawman), first published in 1825, Waterton wrote that this ramshackle building on the banks of the Mibiri Creek (some 20 km up the Demerara River from Georgetown), where once generals and governors had caroused, was now tenanted by the vampire. And some of these tenants lived in the loft where Waterton had slung his hammock, giving him many a fine opportunity of paying attention to [them]. Other bits of text seemingly indicate that he was referring to the common vampire bat Desmodus rotundus (Figure 1) rather than the white-winged vampire bat Diaemus youngi. But what in fact was he referring to? Indeed, Waterton's words reveal that he really had no idea. For instance, he describes how these vampires feed on blood as well as on bananas and on what he thought were wild guavas, and that they were fond of “something” in the flowers of the sawarri nut tree (Caryocar nuciferum). But vampire bats are obligate blood-feeders. Clearly, poor Waterton was getting himself mixed up with some kind of fruit bat… JA Racero Casarrubia/Flickr.com (CC BY-ND 2.0) …and maybe something else. The wingspan of common vampire bats is some 13–15 inches (around 35 cm), but Waterton says his vampires generally measured 26 inches (66 cm) from wing tip to wing tip. One that he killed even notched up 32 inches (over 81 cm)! But even the giant fruit-eating bat Artibeus lituratus (which roosts in trees and old buildings) has a wingspan of only around 18–20.5 inches (46–52 cm). Certainly, an inventory in the Smithsonian National Museum of Natural History (Washington, DC) records one at the latter size. Don Wilson, emeritus curator of mammals at the museum told me that the animal “was cataloged in the field by Charles Handley, a colleague long deceased, and a very careful observer. Relying solely on memories of having handled numerous individuals of A lituratus in the field, I think 521 mm, the actual measurement listed in the record, is not unreasonable”. Not at all, but it's still not long enough. The only South American bat with a wingspan that can match Waterton's 32 inches is the great false vampire bat Vampyrum spectrum, which comes in at a whopping 27.5–39 inches (70–99 cm). But it usually roosts in trees, not lofts, and it's no fruit bat. Rather, it preys on other bats, rodents, and birds. It does, however, have a pronounced nose-leaf, which Waterton described as a curious membrane, which rises from the nose, and gives [the vampire] a very singular appearance. Yet it's hardly singular; there are loads of leaf-nosed bats – including the very same A lituratus and D rotundus. Did Waterton conflate all three species? In my 1891 edition of Wanderings, things then get downright weird with a plate showing three sleeping men being approached by huge flying “vampire” bats with Halloween silhouettes. Certainly, the engraver was little enlightened by Waterton's descriptions since the animals already on the sleepers (suddenly shrunk to about the right size) are feeding on their victims’ chests and thighs, when they really prefer toes and ankles. And this just before Waterton describes how he himself had wanted to be fed upon by a vampire bat, just so he could say he had been! He would even dangle his leg out of his hammock to tempt an attack. The fact that he was never once bitten should have alerted him to his misidentifications, but there you go. It is true that before writing his Wanderings, Waterton managed a Guyanese sugar plantation, connecting him directly with slavery: an experience that led him to denounce the entire concept as a mistake – at least to a point – in the pages of his book. While being careful not to dismiss this complicated history, it is also true that his words opened the eyes of thousands to the wonders of natural history (including a certain young fellow called Charles Darwin) – especially when he got it right! But even in error, Waterton's words may have enriched you with a little more knowledge on the bats of Guyana, always assuming I have my facts straight! One day, just as for that house on Mibiri Creek, Nature will eventually repossess us all; how nice to think that, after it does, someone might learn from our mistakes. Adrian Burton