ARE FRUIT BATS FLYING PRIMATES? ANOTHER RETROSPECTIVE FROM OUT OF THE ARCHIVES

A fruit bat in flight at Sydney's Royal Botanic Gardens, Australia (© Daniel Vianna/Wikipedia – CC BY-SA 3.0 licence)

But when he brushes up against a screen,

We are afraid of what our eyes have seen:

For something is amiss or out of place

When mice with wings can wear a human face.

        Theodore Roethke – ‘The Bat’

The following article of mine was originally published by Fortean Times in its April 1997 issue (and is reprinted in unchanged form below). Yet despite the initially encouraging research documented in it, the passage of time following its publication did not prove kind to the flying primates hypothesis. In more recent years, sufficient evidence against its veracity as obtained via comparative DNA analysis with primates, mega-bats, and micro-bats has been proffered for it to be largely (though not entirely) discounted nowadays by mainstream workers. (A detailed examination of this evidence is presented online here in British palaeontologist Dr Darren Naish’s Tetrapod Zoology blog.) Nevertheless, even though the notion of fruit bats as our winged cousins may have been grounded, zoologically speaking it remains of undeniable historical interest, and was such a charming novelty while it lasted that I couldn’t resist recalling it on ShukerNature as part of my occasional 'Out of the Archives' series – so here it is.

The minute fruit bat Cynopterus minutus with outstretched wings (© Wibowo Djatmiko/Wikipedia - CC BY-SA 3.0 licence)

The fortean literature contains reports of some exceedingly bizarre entities, but few are any stranger than the various bat-winged humanoids spasmodically reported from certain corners of the world. These include such aerial anomalies as the Vietnamese 'bat-woman' soberly described by three American Marines in 1969, the child-abducting orang bati from the Indonesian island of Seram, and the letayuschiy chelovek ('flying human') reputedly frequenting the enormous taiga forest within far-eastern Russia's Primorskiy Kray Territory (click here for further details).

Zoologists have traditionally averted their eyes from such heretical horrors as these, but in a classic 'fact is stranger than fiction' scenario, a remarkable evolutionary theory has lately re-emerged that unites humans and bats in a wholly unexpected evolutionary manner.

FLYING FOXES AS WINGED PRIMATES?

As far back as 1910, W.K. Gregory proposed that bats were closely related to primates - the order of mammals containing the lemurs, monkeys, apes, and humans. More recently, Dr Alan Walker revealed that dental features of a supposed fossil primate christened Propotto leakeyi in 1967 by American zoologist Prof. George Gaylord Simpson indicated that it was not a primate at all, but actually a species of fruit bat.

In 1986, however, Queensland University neurobiologist Dr John D. Pettigrew took this whole issue of apparent bat-primate affinity one very significant step further, by providing thought-provoking evidence for believing that the fruit bats may be more than just relatives of primates - that, in reality, these winged mammals are primates!

Chuuk flying fox Pteropus insularis, PZSL 1882 (public domain)

All species of bat are traditionally grouped together within the taxonomic order of mammals known as Chiroptera. Within that order, however, they are split into two well-defined suborders. The fruit bats or flying foxes belong to the suborder Megachiroptera ('big bats'), and are therefore colloquially termed mega-bats. All of the other bats belong to the second suborder, Microchiroptera ('small bats'), and hence are termed micro-bats.

MACRO-BATS AND MICRO-BATS – NOT SEEING EYE TO EYE?

As a neurobiologist, Dr Pettigrew had been interested in determining the degree of similarity between the nervous systems of mega-bats and micro-bats. In particular, he sought to compare the pattern of connections linking the retina of the eyes with a portion of the mid-brain called the tectum, or superior colliculus. He used specimens of three Pteropus species of fruit bat to represent the mega-bats. And to obtain the most effective comparison with these, he chose for his micro-bat representatives some specimens of the Australian ghost bat Macroderma gigas - one of the world's largest micro-bats. Ideally suited for this purpose because its visual system is better developed than that of many other micro-bats, it has large eyes like those of fruit bats, and retinas with a similar positional arrangement.

The Australian ghost bat, a giant species of micro-bat (public domain)

Pettigrew's examination of all of these specimens revealed that the pattern of retinotectal neural connections was very different between mega-bats and micro-bats, but far more important was the precise manner in which they differed - providing a radically new insight not merely into bat evolution but also into the family tree of humanity.

Reporting his remarkable findings in 1986, Pettigrew announced that the retinotectal pattern of connections in fruit bats was very similar to the highly-advanced version possessed by primates. That fact was made even more astounding by the knowledge that until this discovery, the primate pattern had been unique. In other words, it had unambiguously distinguished primates not only from all other mammals (including the micro-bats) but also from all other vertebrates, i.e. fishes, amphibians, reptiles, and birds - all of which have a quite different, more primitive pattern. Suddenly, the fruit bats were in taxonomic turmoil.

NOT SUCH A FLIGHT OF FANCY?

Until now, the fact that micro-bats and mega-bats all possessed wings and were capable of controlled flight had been considered sufficient proof that they were directly related, because it seemed unlikely that true flight could have evolved in two totally independent groups of mammals. Gliding, via extensible membranes of skin, had evolved several times (e.g. in the scaly-tail rodents – click here for some cryptozoological connections); the 'flying' squirrels; three different groups of 'flying' marsupial phalanger; and the peculiar colugos or 'flying lemurs' – click here), but this did not require such anatomical specialisations as the evolution of bona fide, flapping wings for true flight.

Scaly-tails, one species of which is locally dubbed the flying jackal (public domain)

Yet it seemed even less likely that the advanced retinotectal pathway displayed by primates could have evolved wholly independently in fruit bats.

In short, by exhibiting the latter organisation of neural connections, fruit bats now provided persuasive reasons for zoologists to consider seriously the quite extraordinary possibility that these winged mammals were not bats at all, in the sense of being relatives of the micro-bats. Instead, they were nothing less than flying primates!

Wallace's fruit bats Styloctenium wallacei, 1896 (public domain)

Moreover, as Pettigrew noted in his paper, even the wings of mega-bats and micro-bats are not as similar as commonly thought. On the contrary, they show certain consistent skeletal differences, which point once again to separate evolutionary lines. And even that is not all - thanks to Dermoptera, that tiny taxonomic order of gliding mammals known somewhat haplessly as the flying lemurs (bearing in mind that they are not lemurs, and do not fly!) or, more suitably, as the colugos.

For by combining previously-disclosed similarities in blood proteins between the primates and the flying lemurs with the structural and neural homology apparent between the flying lemurs' gliding membranes and the wings of the mega-bats, extra evidence is obtained for a direct evolutionary link between fruit bats, primates, and the flying lemurs - thus resurrecting another possibility that had been suggested by researchers in the past.

FACING UP TO THE FACTS

One of the most familiar external differences between mega-bats and micro-bats is the basic shape of their face.

The remarkably lemur-like face of a Pteropus fruit bat (public domain)

Whereas the face of most fruit bats is surprisingly vulpine (hence ‘flying fox’) or even lemurine, in many micro-bats it is flatter in shape - though in some species, evolution has superimposed upon this shape all manner of grotesque flaps and projections.

The uniquely grotesque face of the aptly-named Antillean ghost-faced bat Mormoops blainvillii, a species of micro-bat native to the West Indies (public domain)

The lemur-like shape exhibited by the face of many fruit bats has traditionally been dismissed as evolutionary convergence, engendered merely by these two mammalian groups' comparable frugivorous tendencies.

Judging from Pettigrew's revelations, however, there may now be good reason to believe that such a similarity is a manifestation of a genuine taxonomic relationship between lemurs and fruit bats. The faces of the flying lemurs are also very lemurine (hence their name), which ties in with the above-noted serological evidence for a direct, flying lemur-primate link.

A colugo or flying lemur, again presenting a very lemurine face (hence its name) (public domain)

Thought-provoking indeed is the evidence for believing that fruit bats are legitimate, albeit aerially-modified, offshoots from the fundamental family tree of the primates. As Pettigrew pointed out, it is highly implausible that the reverse theory is true (i.e. that the fruit bats gave rise to the primates), because fruit bats seem to be relatively recent species, first evolving long after the primate link had emerged.

EVIDENCE FOR AND AGAINST FLYING PRIMATES

Inevitably, no theory as radical as one implying primate parentage for the fruit bats will remain unchallenged for very long. In 1992, for instance, molecular biologist Dr Wendy Bailey and two other colleagues from Detroit's Wayne State University School of Medicine announced that DNA analysis of the epsilon(e)-globin gene of both groups of bats, primates, and a selection of other mammals implies that the two bat groups are more closely related to one another than either is to any other mammalian group. This finding would therefore seem to support the traditional bat classification., but as noted by proponents of Pettigrew's ideas, it does not explain the extraordinary development by fruit bats of the primates' diagnostic visual pathway. Consequently, this tantalising physiological riddle currently remains unanswered.

Moreover, in a comparative immunological study whose results were published during 1994, Drs Arnd Schreiber, Doris Erker, and Klausdieter Bauer from Heidelberg University showed that proteins in the blood serum of fruit bats and primates share enough features to suggest a close taxonomic relationship between these two mammalian groups after all - thus bringing this continuing controversy full circle.

Samoan fruit bats Pteropus samoensis, 1858 (public domain)

Many primitive tribes believe that fruit bats are the spirits of their long-departed ancestors. In view of the fascinating disclosures reported here, these tribes could be closer to the truth than they realise!

This ShukerNature blog article is excerpted from my book Karl Shuker's Alien Zoo – a massive compendium of my Alien Zoo cryptozoological news reports and my longer Lost Ark cryptozoological articles that have been published in Fortean Times since the late 1990s.

SOLVING THE MYSTERY OF SCHOMBURGK'S MISSING MICRO-SQUIRRELS - AND REVISITING TANZANIA'S FLYING JACKAL

Large-eared flying mouse Idiurus macrotis (Jonathan Kingdon - Kingdon Field Guide to African Mammals)

It's often been said that good things come in small packages, and this is certainly true of the following cryptozoological case, in which the cryptid in question may be minuscule but is definitely no less memorable for that.

The German explorer/naturalist/film-maker Hans Schomburgk (1880-1967) earned a lasting, well-deserved place in zoological and cryptozoological history by rediscovering on 13 June 1911 the pygmy hippopotamus Choeropsis liberiensis, alive and well in Liberia – where it had long been known to the native people as the nigbwe, yet had been ignored by scientists.

Pygmy hippopotamus (Cliff1066/Wikipedia)

Indeed, until then this enigmatic species had generally been discounted as nothing more than a freak of nature, consisting merely of dwarf, stunted specimens of the larger, common hippopotamus Hippopotamus amphibius, or even as a juvenile form of the latter – despite American zoologist Dr Samuel G. Morton having officially named and described it as a valid, second species of hippo more than half a century earlier in 1849. Following its rediscovery by Schomburgk, however, studies confirmed its status as a valid and very distinct species in its own right. (For full details concerning the pygmy hippo's controversial history, see my book The Encyclopaedia of New and Rediscovered Animals (Coachwhip: Landisville, 2012).)

These were the first live pygmy hippos that I ever saw, at Bristol Zoo during the late 1960s/early 1970s (Maurice Beere)

Yet whereas Schomburgk became famous for refinding this erstwhile cryptid, it was by no means the only creature of cryptozoology that he had heard about during his numerous African expeditions. In his book Zelte in Afrika ('Tents in Africa'), published in 1957 but looking back upon his explorations and researches from the past six decades, he documented a number of very interesting mystery beasts, some of which were new to me when they were brought to my attention recently by German cryptozoological investigator Markus Bühler.


Although I'd heard of Schomburgk's book, and had read a little concerning his cryptozoological accounts in other publications, I'd never seen a copy of it. Nor had I received any excerpts or summaries from it, until Markus very kindly provided me with the following information:

"There are so many cryptids in Schomburgk´s "Zelte in Afrika", including some he has seen himself, which were nowhere else documented...

"He wrote for example he once encountered several small mammals which looked like tiny squirrels, and which were extremely tame. They were so cute he didn't want to kill one for his collection, and later he learned these animals were never seen before (and never again)...

"There were also some stories which he heard from natives, but without further information, about a giant hyaena, a "jungle tiger" and I think also a mokele-mbembe-like animal. If I remember correctly he also brought a sculpture of some kind of water monster back to Germany, which was in the archives of the ethnological museum at Hamburg, but later given back (but there is still a copy I think). It's already been some time ago since I read the book the last time, but there are really a whole lot of great stories, and a lot of information about water elephants."

As I was so intrigued by the tantalising snippets above, Markus checked through his copy of Zelte in Afrika for further details, and this is what he found:

"Luckily I have put a bookmark at the pages which mention some cryptids.

"So here are some animals which are sadly only mentioned: the lion-tiger (not jungle tiger as I thought) of Senegal, the giant hyaena, the water-leopard [of] Mafue [near Zambia's Lukanga Swamp] which is depicted in the sculpture he discovered.

"He also heard reports about chimpekwe [aka chipekwe] at Lake Bangweulu [in Zambia].

"He mentions also a creature called koo-be-eng, some kind of giant snake-like reptile with a horn on its head, which lives in the water and eats big animals. He wrote that there is a depiction of such a beast in a cave at Brackfontein [in South Africa].

"There is also kou-teign-koo-rou - lord of the water, which was said to be bigger and stronger than a hippo and also living in swamps.

"Bushmen caught it with very strong traps, and he mentions also depictions.

"He also heard tales about the animal tu from the upper part of Morfi River [in Liberia], which was said to be as big as a goat, with teeth of a dog, black fur, and to be quite vicious.

"And a giant ape from Vey-Land which was like a huge greyish yellowish chimp with long fur, which kills or mutilates humans."

Although all of these beasts sounded very interesting (I was already aware of the tu, chipekwe, and water leopard, but not the others), the one that fascinated me most was the Liberian micro-squirrel. For although Schomburgk had stated that these delightful little creatures had never been seen again since his encounter with them, they instantly reminded me of an obscure but formally-described and definitely still-surviving species that I had read about somewhere else. So I asked Markus if he could provide me with a translation into English from Schomburgk's book of the entire passage describing them, and here it is: (Thanks, Markus!)

"During my search for Choeropsis liberiensis I found a bush which was full of lovely small animals. Full of beans, they were. They were grey-brown coloured, reminiscent of tiny squirrels. I put my hand in the bush. The tiny cute beasts whizzed on my palm, stood upright like small rabbits and jumped from finger to finger. Noticeable was the long tail, with feather-like erected hairs. When I tried to hold one on it, it broke off. I repeated this experiment, but always with the same result, so brittle was this, with a thin skin-covered chain of tiniest vertebrae. Surely they were some kind of pygmy mouse. As I was on a hunt, I had no vessel with me, in which I could have caught one of the beasties alive. Only the spirit jar, which one of my native helpers carried. I let him uncap it, to include at least one or two of these beings in my collection. But at this moment the tiny mice looked at me with their big wide eyes in such a clever trusting way, I had not the heart to exploit their trust in the giant who was so mysterious to them. It doesn't have to be today, I thought. I will come back tomorrow or the day after tomorrow and incorporate the lovely bush pygmy mouse into my menagerie. But never again, neither back then nor later, have I or any other explorer found any sign of this odd little animal. And what grieves me most: since then, I have learned that I'd had an animal in my hand that had never been seen in my homeland and which was unknown to science. I have enriched zoology with some discoveries: the Bubalus schomburgki (a type of Liberian buffalo), the already mentioned shell Mutela hargeri schomburgki, five species of earthworm, from which two have my name as well. However, my lively little mouse belongs to those animals that exist yet which have still not been secured for science."

After reading this account, conversely, I was even more convinced that I knew the identity of Schomburgk's mystifying little mammal, because many years earlier I had read about another famous naturalist not only seeking but successfully encountering what seemed to be an identical mini-beast elsewhere in West Africa. The book in which this search appeared was The Bafut Beagles (Rupert Hart Davis: London, 1954), recounting the author's many adventures during a private expedition to Cameroon in 1949, collecting wild animals to sell to zoos. And the name of that author? None other than Gerald Durrell.

 
My much-treasured Penguin paperback edition of The Bafut Beagles (the very first Gerald Durrell book that I ever read, and which swiftly led to my devouring each and every other book written by him!)

One creature that Durrell was particularly anxious to find and collect while in Cameroon belonged to a fascinating but scarcely-known genus of rodents – Idiurus, the flying mice (a somewhat unfortunate name, as they are not mice, and they glide rather than fly!). And the species of Idiurus that he was seeking was I. kivuensis (which, as will be seen, has a somewhat convoluted taxonomic history).
Idiurus kivuensis as depicted in The Bafut Beagles (Ralph Thompson)

Idiurus is one of three genera of squirrel-like rodents belonging to the taxonomic family Anomaluridae. Exclusively African, this family's members are known collectively as anomalures ('strange tails') or, more colloquially, as scaly-tails, because they are all characterised by two rows of overlapping keeled scales on the underside of their tail near the base. Moreover, all but one species (the flightless Cameroon scaly-tail Zenkerella insignis) also possess a pair of gliding membranes, linking their front and hind limbs on each side of their body.

Three species of scaly-tail, including both species of flying mouse (Jonathan Kingdon - Kingdon Field Guide to African Mammals)

Consequently, scaly-tails superficially resemble true flying squirrels or petauristids, but their cranial structure is very different, so they are only distantly related to those latter rodents. Instead, their outward similarity is due to convergent evolution (so too is that of the even more distantly related flying phalangers - a group of squirrel-like gliding marsupials native to Australia).

The smallest scaly-tails are the so-called flying mice or pygmy scaly-tails, belonging to the genus Idiurus. Today, only two species are recognised – I. macrotis, the long-eared flying mouse (formally described in 1898, and native to western and central Africa, ranging from Sierra Leone to the Democratic Republic of Congo); and I. zenkeri, Zenker's flying mouse (formally described in 1894, and native to central and central-west Africa, ranging from Cameroon to the Democratic Republic of Congo).

Zenker's flying mouse (Eveha/Wikipedia)

At the time of Durrell's expedition, however, a third species was also recognised – I. kivuensis, the Kivu flying mouse. When this was originally described in 1917 by Swedish mammalogist Dr Einar Lönnberg, he had categorised it as a subspecies of I. zenkeri, but in 1946 mammalogist Robert W. Hayman from London's Natural History Museum had elevated it to the level of species. Thus it remained until 1963, when it was reclassified by Belgian mammalogist Prof. Walter N. Verheyen as a subspecies of I. macrotis, a status that it has retained ever since.

So the Idiurus that Durrell encountered in Cameroon during his 1949 expedition there - and documented in a charmingly entitled chapter 'The Forest of Flying Mice' within his book - is nowadays deemed to be a subspecies of Idiurus macrotis, the long-eared flying mouse.

Long-eared flying mouse Idiurus macrotis (Ed Stauffacher/Grzimek's Animal Life Encyclopaedia)

And here is Durrell's description of the very first specimen that he succeeded in capturing:

"He was about the size of a common House Mouse, and very similar to it in general shape. The first thing that caught your attention was his tail: it was very long (almost twice as long as his body), and down each side of it grew a fringe of long, wavy hairs, so the whole tail looked like a bedraggled feather. His head was large, and rather domed, with small, pixie-pointed ears. His eyes were pitch black, small, and rather prominent. His rodent teeth, a pair of great bright orange incisors, protruded from his mouth in a gentle curve, so that from the side it gave him a most extraordinarily supercilious expression. Perhaps the most curious part about him was the 'flying' membrane, which stretched along each side of his body. This was a long, fine flap of skin, which was attached to his ankles, and to a long, slightly curved, cartilaginous shaft that grew out from his arm, just behind the elbow. When at rest, his membrane was curled and rucked along the side of his body like a curtain pelmet; when he launched himself into the air, however, the legs were stretched out straight, and the membrane thus drawn taut, so that it acted like the wings of a glider."

Later on, by smoking a tree containing more Idiurus specimens in the hope of capturing some without harming them, Durrell was able to see these tiny creatures take to the air, and what a remarkable sight it was:

"I have seen some extraordinary sights at one time and another, but the flight of the flying mice I shall remember until my dying day. The great tree was bound round with shifting columns of grey smoke that turned to the most ethereal blue where the great bars of sunlight stabbed through it. Into this the Idiurus launched themselves. They left the trunk of the tree without any apparent effort at jumping; one minute they were clinging spread-eagled to the bark, the next they were in the air. Their tiny legs were stretched out, and the membranes along their sides were taut. They swooped and drifted through the tumbling clouds of smoke with all the assurance and skill of hawking swallows, twisting and banking with incredible skill and apparently little or no movement of the body. This was pure gliding, and what they achieved was astonishing. I saw one leave the trunk of the tree at a height of about thirty feet. He glided across the dell in a straight and steady swoop, and landed on a tree about a hundred and fifty feet away, losing little, if any, height in the process. Others left the trunk of the smoke-enveloped tree and glided round it in a series of diminishing spirals, to land on a portion of the trunk lower down. Some patrolled the tree in a series of S-shaped patterns, doubling back on their tracks with great smoothness and efficiency. Their wonderful ability in the air amazed me, for there was no breeze in the forest to set up the air currents I should have thought essential for such intricate manoeuvring."

Idiurus airborne, as depicted in The Bafut Beagles (Ralph Thompson)

As its common name suggests, a flying mouse does indeed look very murine in general form, because when at rest its gliding membranes are folded up tightly and thus are not readily noticeable (which would explain why Schomburgk never mentioned them). What is noticeable, conversely, as mentioned by Durrell, is its very lengthy, plumed tail, which is so fragile that it could certainly be snapped off if not handled with great care.

Moreover, whereas most scaly-tail species are solitary, those of Idiurus are colonial; indeed, the two Idiurus species have even been found associating together. In 1940, for instance, veteran American cryptozoologist and animal collector Ivan T. Sanderson recorded finding approximately 100 individuals of both Idiurus species living together in the same tree during his participation in the Percy Sladen Expedition to the Mamfe Division of Cameroon.

Idiurus ahoy! (Illustration source unknown)

Due to their primarily nocturnal lifestyle and highly elusive nature, however, even today the Idiurus scaly-tails remain virtually unknown not only to science but even to local hunters – as Durrell discovered during his Idiurus searches in Cameroon.

In conclusion: as can clearly be seen from the above accounts, the long-eared 'flying mouse' scaly-tail I. macrotis, whose zoogeographical range includes Liberia, so greatly resembles Schomburgk's description of his mysterious Liberian micro-squirrel that there can be little doubt the two mammals are indeed one and the same species – an opinion shared by Markus after I'd informed him of my thoughts concerning this case. Another longstanding if hitherto little-known cryptozoological mystery is duly solved, but many others documented by Schomburgk remain unresolved – for now!

Interestingly, this is not the first time that a scaly-tail has been at the core of a cryptozoological mystery, as ably demonstrated by the remarkable case of Tanzania's flying jackal - which I originally investigated in my book Extraordinary Animals Worldwide (1991) and returned to in its updated edition, Extraordinary Animals Revisited (2007).

Late 19th-Century engraving of a large Anomalurus scaly-tail

As reported by Captain William Hichens in the December 1937 issue of a monthly magazine entitled Discovery, kraalsmen in what was then Tanganyika (now Tanzania) affirmed that an amazing beast known to them as the mlularuka or flying jackal, yet wholly unknown to science at that time, would frequently raid their mango trees and pomegranates during its flights at dusk, and would give voice to loud cries while on the wing. Not surprisingly, their reports were totally disbelieved and dismissed as arrant fantasy - until the ‘flying jackal’ was discovered!

A selection of scaly-tails (Clifford Lees, in A.H. Booth's Small Mammals of West Africa)

As I learnt from Dr Maria E. Rutzmoser of Harvard University’s Agassiz Museum, in 1926 zoologist Arthur Loveridge was in Tanganyika, collecting specimens for the museum, and at Vituri he succeeded in tracking down the mlularuka, but it was not a flying jackal. Instead, it was a large (2.5-ft-long) form of scaly-tail.

Although well-known in West and Central Africa at that time, their existence in East Africa had not previously been suspected. Consequently, the mlularuka was initially believed to be a new species, but was later shown to be a subspecies of an already wide-ranging species variously called Lord Derby's or Fraser’s scaly-tail Anomalurus derbianus. Hence it is now referred to as A. d. orientalis - a mythical flying jackal that was ultimately unmasked as an aerial squirrel-impersonator!

Lord Derby's (aka Fraser's) scaly-tail (Eveha/Wikipedia)

My sincere thanks to Markus Bühler for so generously sharing information from Schomburgk's book with me and also for very kindly supplying me with an English translation of the relevant passage from it concerning the Liberian micro-squirrels.