November 1, 2012 | 34
Of the world’s 5700-odd living species of mammal, more than 1200 are bats, making them the most speciose mammalian group after rodents (of which there are about 2200 species). Bats are phenomenally diverse and occur in most terrestrial environments around the world. Understandably, they’re often compared to birds, and several bat groups – those that eat fruit and those that hunt insects and birds on the wing – are undeniably similar, in ecology, behaviour and some features of anatomy, to some bird groups.
But in one very special respect, bats and birds are remarkably different. Birds have evolved flightlessness on innumerable separate occasions. There are not only such classic flightless bird groups as penguins, dodos, ostriches, emus, kiwi and so on, but also flightless ducks, geese, swans, ibises, cormorants, grebes, cranes, rails, auks, falcons, parrots and songbirds (and this isn’t a complete list).
Yet bats, so far as we know, have never evolved flightlessness, despite a history that extends over more than 50 million years, despite the invasion of island ecosystems where flightlessness in birds was incredibly common, and despite an enormous amount of variation in size, ecology and wing form (check out the stupid short wings on the flat-headed bat shown in the adjacent image). The absence of flightless bats from both the modern fauna and the fossil record is weird, but perhaps explainable (read on).
I’m a big fan of speculative zoology, and one meme among the many that populates the world of spec zoo is that of the giant flightless bat (note that, for bats, ‘giant’ means ‘more than a few kg’). As we’ll see, various flightless bat species have appeared in speculative books, TV shows and on websites. The creators of these hypothetical animals have placed them in the far future where things are very different from today. They’re not just giant flightless bats – they’re giant flightless bats from the future.
Speculative zoology more or less went mainstream in 1981 with Dougal Dixon’s After Man (Dixon 1981). Set 50 million years in the future, After Man describes a future Earth inhabited by assemblages of entirely new animals, many of which have evolved from those tough generalists most likely to truly survive the human era (like rats, rabbits and crows). Among the most memorable creatures of Dixon’s future Earth are the flightless bats that have evolved on the Pacific archipelago of Batavia.
Arriving and radiating on the islands before birds were able, the Dixonian future-bats have managed to fill niches in terrestrial, arboreal and marine environments. The most fantastic is the Night stalker Manambulus perhorridus, a bipedal predator about 1.5 m tall that “roams screeching and screaming though the Batavian forest at night in packs”, over-powering mammal and reptile prey. Night stalkers walk on their stumpy hands, their prehensile feet hanging over their shoulders. All traces of wing membranes have been lost, and massive ribbed eared and a huge, spear-shaped nose leaf provide them with excellent echolocation abilities and compensate for their blindness. Batavia is also populated by the seal-mimicking Surfbat Remala madipella, the predatory, tree-climbing Shalloth Arbovespertilio apteryx, and the Flooer Florifacies mirabila. Surfbats are sleek-furred swimmers that cruise underwater with shortened, muscular wings and tail-flaps while shalloths are entirely wingless, sloth-like omnivores with mitten-like hands and a single stabbing claw on each thumb.
The Flooer is a largely sedentary, insectivorous, flightless bat that grows large fragrant ear and nose flaps that mimic flower petals. Flooers sit among flowers, attracting insects and eating them. This description is curious, since it’s uncannily similar to that of another hypothetical mammal of the speculative literature: the Miraculous flower-faced snouter Cephalanthus thaumasios.
Snouters – properly termed rhinogradentians – were famously invented for Harald Stumpke’s 1957 book Bau und Leben der Rhinogradentia, republished in English in 1967 as The Snouters: Form and Life of the Rhinogrades (Stumpke 1967). When I first learnt of the Flooer I assumed, reasonably I think, that Dixon had been inspired by Cephalanthus. After asking him I have to conclude that the two creatures really had ‘evolved’ in parallel: when writing After Man, Dougal had been completely unaware of Stumpke’s book. It’s widely acknowledged that Dixon is the ‘go-to guy’ for speculative zoology, so we all had high hopes for his more recent project: the 2002 TV series The Future Is Wild (see Dixon & Adams 2004). One giant bat did feature in the series – a desert-adapted scavenger termed the Deathgleaner – but it was far from flightless, being a vulture-like soarer with a substantial wingspan.
More recently, a few speculative zoology blogs and websites have also featured flightless or near-flightless future bats. Tim Morris’s Conceptual Zoology features the mouse-sized Running bat Cursochiropteryx diabolis, while Dee Dee Rivera’s Metazoica includes a penguin-like swimming bat and a variety of climbing and ground-running flightless bats – termed cryptopters – endemic to the Hawaiian Islands.
Descendants of fruit bats, cryptopters include lemur-like, sloth-like and superficially deer-like species, all of which lack any trace of wings, have partially fused fingers, and live in fear of the gigantic flying, predatory bat Cercomoloch.
The biggest speculative giant flightless future bat news of recent years has been the 2007 debut of a nefarious super-predator that has an important role in the various story arcs of the ITV drama series Primeval (five seasons have run so far, the most recent of which was screened in May and June 2011).
Known only as ‘Future Predator’, the creature concerned is a quadrupedal, long-limbed animal about similar in size to a lion. It’s able to climb, leap, run and rear up bipedally; it walks on its knuckles, has atrophied eyes and (despite lacking obvious external ears) relies almost entirely on echolocation. My first thought on seeing this creature on the TV in 2007 was that it must surely be a giant, macropredatory, flightless bat from Earth’s distant future, and the explanation provided in the episode and accompanying documentary revealed that this is exactly what it is. The designers and animators must be congratulated for creating an imaginary animal that really does have bat-like qualities, despite its size, flightlessness and weird appearance. It runs and springs like a gigantic vampire bat. Storylines involving ‘Future Predator’ have become increasingly complex and involve the efforts of some humans to use the animals as weapons, a temporal paradox regarding the origin of the species, and contamination and alteration of Earth’s timeline following the passage of some of these animals into the geological past.
Surfbats, night stalkers, cryptopters and Future Predators are, obviously, all very much denizens of fiction. Why haven’t real-world bats ever become flightless? It’s been argued that bat anatomy – involving, as it does, extensive wing membranes and sprawling limb postures – would make the transition to flightlessness a difficult one. However, the main reason may be that bats have simply never had the evolutionary opportunity to lose flight: it has remained crucial to their need to capture prey, to migrate and to avoid predators. And the fact that birds have remained a constant presence throughout the whole of bat history, and have proved even better at colonising remote islands than have bats, probably means that bats have never been ‘released’ from the pressures of predation. Indeed, even bats that are superb aerialists suffer heavily from predation by owls and hawks [adjacent Greg Capullo image from Don’t Forget a Towel].
So, while some bats (notably the Australasian short-tailed bats or mystacinids) are highly able scuttlers and runners, able to fold their wing membranes tightly away, my informed guess is that birds would need to be eliminated before bats could become truly flightless. That might happen one day, but it won’t be anytime soon.
Previous Tet Zoo articles have covered some of the issues touched on here. For more, see…
Refs – -
Dixon, D. 1981. After Man: A Zoology of the Future. Granada, London.
- . & Adams, J. 2004. The Future Is Wild. Dorling Kindersley, London.
Norberg, U., & Rayner, J. 1987. Ecological morphology and flight in bats (Mammalia; Chiroptera): wing adaptations, flight performance, foraging strategy and echolocation. Philosophical Transactions of the Royal Society B: Biological Sciences 316, 335-427.
Nowak, R. M. 1999. Walker’s Mammals of the World, Sixth Edition. The Johns Hopkins University Press, Baltimore and London.
Stumpke, H. 1967. The Snouters: Form and Life of the Rhinogrades. The Natural History Press, New York.