Ten Million Aliens

by Simon Barnes

  True flight. That’s the thing about bats. We’ve met some of the gliders and swoopers. I’ve always loved watching flying squirrels make their reckless and apparently doomed journeys across forest clearings, but for all their ingenuity and dexterity the general direction of each journey is down. Gliding is really just falling with attitude. But bats fly under their own power. When a bat is up it stays up.

  You see them in England as flickering shadows caught in the tail of your eye: flying things that don’t move quite like other flying things. Partly it’s because they are so agile, especially laterally: you see them jink sideways, with no effort at all, to catch an insect, seizing it in a leathery embrace of the wings and whisking it mouthwards. I remember a bat moment in Brisbane, where I was covering the cricket (English bats not faring too well that day) for The Times, part of the sportswriting side of my life. There is a small relict patch of mangrove swamp in the Brisbane River, so naturally, I took a twice-daily detour through there on my way to and from the ground. One evening, I left the cricket-ground later than usual. It was getting dark by the time I stepped onto the boardwalk. As if at a signal, the crickets struck up in unison, a high, mad, electrophonic squeal like an alien weapon sending the whole world crazy in a science-fiction film. At more or less the same instant huge shapes appeared in the sky and powered towards me, strong and majestic, eventually flying directly overhead: vast, arched, measured wingbeats: big fruit bats on their way to a night’s plunder. They gave the city a richness it hadn’t had before.

  And a slightly sinister touch, of course. We humans find all the creatures of the dark a little difficult, and give them all kinds of frightening attributes. Owls are birds of ill omen in Europe; birds of death, in Africa. Nightjars are surrounded by strange names and curious legends. Bats terrify the life out of people. The association of bats with vampirism goes very deep, even though there are 900-plus species of bats that have nothing to do with blood, and those that do are pretty small. I suspect it’s something to do with the naked skin of the bat’s wing: so unbirdlike. People from bat groups who try and help people with bat roosts in their outbuildings or (scarier still) in their attics will all tell you the same thing. They will catch a bat and show it to the householders, who see the furriness of the body and the bright mammalian eyes. Oh, it’s just like a little mouse! And with this revelation the bat becomes tolerable, even agreeable. Strange, in a way: we humans go in for naked skin rather than furriness: but the naked skin of the bat repels while the furriness makes it acceptable. DH Lawrence wrote a poem about it; here are the closing lines:

  Wings like bits of umbrella.

  Bats!

  Creatures that hang themselves up like an old rag, to sleep;

  And disgustingly upside down.

  Hanging upside down like rows of disgusting old rags

  And grinning in their sleep.

  Bats!

  In China the bat is symbol for happiness.

  Not for me!

  A bat is defined by flight. Flight is not a bonus: flight is all and everything to a bat. They come in two suborders, which might loosely be described as little buggers and bloody great big buggers. The big ’uns, the Megachiroptera or flying foxes, comprise a single family. They can weigh up to 3 pounds, 1.3 kilos, and look very impressive, especially when flying across the Brisbane River. Of these, only one genus uses echolocation, and a fairly crude version of it; the rest rely on their excellent sight.

  The Microchiroptera contains everything else: proper bats, you might say, echolocating and flying. The two things are very closely linked. Both are expensive in terms of energy, but when echolocation is used in flight, synchronised with the wingbeats, it becomes far more economical. In short, for a bat in flight echolocation becomes a freebie. This is the breakthrough that has allowed bats to prosper in so many places across the world: within the Arctic Circle and over almost every bit of land on earth. They are only absent in Antarctica and a few very remote islands. In New Zealand, the Azores and Hawaii, they are the only native mammals; that’s to say, the only mammals not brought there by humans. This has led to such unexpected creatures as the New Zealand short-tailed bat, which drops to the ground and scurries about like a mouse wearing a cape, ground-feeding in the manner of shrew.

  In most circumstances a bat will let out a single echolocating squeak with every wingbeat: up to 15 every second. The problem of echolocation is the same as the problem with radar: you have to find a way of not hearing your own sound. A bat has to shout and listen at the same time, and this is accomplished by means of a muscle in the inner ear that acts like an earplug, switching itself on and off so that the bat hears only the echoes, which it uses to build a sonic world-picture in its brain. Bats are also able to compute out the Doppler shift: the phenomenon that distorts sound when it is mixed with high speed (the change in note you can hear from a passing racing car).

  Bats are capable of high energy and very low energy, and they inhabit the extremes of the temperature spectrum as a result. They can reach 41 degrees Celcius in flight; they can go torpid and drop to 2 degrees at rest. Flight and echolocation mean that the night is theirs: and therefore, they have the great food resource of night-flying insects almost to themselves. Flight is expensive in energy terms, but distance becomes relatively cheap: it is harder to fly for an hour than to run for an hour, but it is easier to fly a mile than to run a mile. That is the conundrum that gives bats the range they need to exploit this resource. But insects aren’t the only food. Some bats take fish, frogs, other bats. Many (not just the flying foxes) take fruit, also nectar. As a result, some trees and many cacti are bat-pollinated, a concept that disturbs our sense of what is right.

  But not half as much as the thought of bats that drink blood.

  Lacing Venus’s girdle

  Obscure and heartbreakingly beautiful, the Ctenophora propel themselves through the world’s oceans on tiny beating hairs called cilia (getting cilia, in other words). Their name means comb-bearer; they are sometimes called comb jellies, sometimes sea gooseberries. Their beauty comes from their colour: most species are bioluminescent; that is to say the produce their own light and they glow. But there is a still lovelier thing that some of them do: as they waft themselves through the seas with their cilia, they can produce shifting rainbows that run up and down their bodies; ask YouTube to find you Ctenophora. This is not colour they produce themselves; it is a trick of the light, or if you prefer a more grown-up explanation, it is a phenomenon of physics called diffraction.

  The Ctenophora make up a phylum of their own. Quite a lot of them are quite a lot like cnidarians, the corals, sea anemones and jellyfish we have already met in these pages, but the differences are marked enough to separate them. Like the cnidarians, their body is a mass of jelly, with a layer of cells outside and another as a lining. But the outer layer is two cells deep in ctenophores, rather than the one in cnidarians. They operate in a similar way: both need water to flow through the body cavity for digestion and respiration, and they have a decentralised network of nerves rather than that brain thing some of us have.I Some scientists used to put the two in the same phylum, but the current trend is to consider them separately.

  They are predators. Hard to believe it: they look like harmless drifting patches of loveliness. Unlike cnidarians, they don’t have any stinging cells, but they possess sticky cells that they use to catch prey, often at the end of tentacles. Microscopic larvae and small crustaceans are their main diet and they can eat ten times their own body weight in a day: which seems like a lot for a lightshow to eat. There are between 100 and 150 species described.

  If they’re not cnidarians, what are they? Some have seized on evidence, most notably the anal pores, and suggested that this indicates a strong affinity with animals with bilateral symmetry (as opposed to the radial symmetry of a jellyfish). Bilaterans include insects, worms, snails and all us vertebrates. There are molecular data that contradict this, but not strongly enough to settle the argument.

>   Most Ctenophora are free-swimming, though there is one group that creeps along the bottom. They occupy all parts of all oceans: from poles to tropics, from surface to benthic depths, from inshore waters to the open ocean. Most are pretty small, a few millimetres in length, but out in the open ocean there are some whoppers, a metre and more across. They are so fragile that you can’t catch them in a net: they just fall apart. One species is an absurdly lovely thing called Venus’s girdle: more like a piece of abstract elegance designed to recall a wing than a living creature. Fossil Ctenophora have been found in Devonian rocks, and fossils very like Ctenophora go right back to the Cambrian.

  I believe I once swam with a swarm of Ctenophora, snorkelling off a beach in Barbados when playing truant from an assignment to cover the cricket. They were mostly transparent, so much so that they almost weren’t there at all. There was a sweetness and innocence about them that I mistrusted entirely: not knowing what I was dealing with, I flipped my fins and changed direction. I think now that this was a bit windy of me: human deaths by sea gooseberry are very rare.

  * * *

  I. What is described by Woody Allen in The Sleeper as “my second favourite organ”.

  The altruistic vampire

  If humans were more like vampire bats the world would be a much happier place. It’s altruism I’m talking about here: the free giving of something; something you need for yourself but are prepared to surrender to another. We humans like to think that altruism in any form is uniquely human: a real and above all moral division between us and the rest of the Animal Kingdom. Vampire bats contradict this view.

  I really do mean altruism. Giving to blood relations doesn’t count. It isn’t altruism to surrender things for your children: that’s just self-interest at the genetic level. The old notion that charity begins at home is a rejection of charity. It’s only when you give – free, gratis and for nothing – to an unrelated individual that you can claim genuine altruism. And it is the bedrock of the society of vampire bats.

  Vampire bats do at least drink blood. All kinds of fanciful legends have built up around them, but that part of it is not made up. There are three species; the white-winged vampire and the hairy-legged vampire prefer the blood of birds, and are adept at clambering through the branches to reach nests and nestlings. Common vampires – we’ll call them plain vampires from here on – prefer the blood of mammals: mostly livestock in these modern times, horses and cattle; their wild prey is tapirs, deer, peccaries and agoutis. They will on occasions drink human blood. The bite is not painful (apparently), but there is a problem in that 0.5 per cent of vampires carry paralytic rabies.I The bats can also contract the disease, and populations sometimes crash as a result of infection. Vampires are pretty small: 9 cm or 4 inches long, a wingspan of 18 cm, 7 inches. They are adept on the ground, crawling with agile speed to reach the target and search out a convenient blood vessel. They use razor-sharp incisors to remove the skin; the resulting wound has been described as looking like a golfer’s divot.

  The anti-coagulant in their saliva allows the blood to flow, and they lap up the trickling blood like a pussycat with a saucer of milk. They weigh about 40 grams; they can take a meal of half their own body weight.

  This sounds as if all the odds favour the bats, but not so. It’s quite common for a vampire to go through a night without a meal. This is inconvenient, to say the least: a vampire can starve to death in three days, and a hunger-weakened bat obviously finds it harder to find food. Blood-hunting is a skill that improves over time: yearling bats will fail one night in three; more experienced animals will only fail one night in ten. But all the same, failure is a fact of life for even the best blood-hunter.

  Vampires are social creatures, coming back to the same day-roost at the end of every night. There are some big colonies, up to 2,000 animals, but most are much smaller, and centre on a core population of females. Some of them will be related, others not: females often change their day-roost at some stage in their lives. All members of a roost, then, related or not, are likely to know each other well. And so it happens that a bat who has failed to find blood in a night’s flying will beg a meal from a neighbour. From a friend, we would say, if we weren’t so terrified of sounding anthropomorphic. The friend will then regurgitate blood, thus sharing a meal. Under this system females have been known to live for 15 years.

  Reciprocal altruism is still altruism; obviously this is a system that works on a mutual back-scratching basis. Rival journalists at a football match, heads down and writing hard, often miss the goal and the goal-scorer. “Christ, who scored?” is a cry of pain that goes up almost every time the ball hits the net. We who saw it never keep the information to ourselves: after all, it’ll be us next time. Human society – humane society – depends on the small kindnesses that you perform as a matter of course and that you expect to be performed for you in turn. But it’s not just humans who are humane.

  * * *

  I. Gerald Durrell, forgetting this fact, tried very hard to get bitten when he travelled in South America, sleeping with his foot sticking out from his bedding. He was anxious for the experience, in the interest of science and as ever, in search of a good story. He remembered about the rabies after a couple of frustratingly unbitten nights.

  Here be mud dragons

  The smartest thing mud dragons ever did was come up with a retractable head. They use it for getting about: unusual use for a head but they are unusual animals. First they unretract the head by filling it with body fluid. Then they anchor it: it is profusely equipped with spines called scalids. Once anchored, they retract the head again: and behold, the dragon has dragged itself forward. This is the phylum of Kinorhyncha, which means moveable snout. The name mud dragons makes them sound rather more glamorous than they really are: tiny scraps of life, the biggest no more than a millimetre in length, living in mud and sand at the bottom of the sea and feeding on the even tinier scraps of organic matter they find there. Their limbless bodies are divided into 13 little chunks called zonites: you can argue, should you wish to, about whether or not these are true segments.

  Their bodies are covered with a tough cuticle which they moult a few times as they grow to adulthood. Some have simple ocelli – basic eyes – on their heads. There are 180 species described, and they can be found in marine mud from the intertidal zones to depths of 8,000 m, and from Greenland to Antarctica. They are simple and effective creatures. They didn’t have the potential or perhaps more likely, they just lacked the breaks needed for great complexity and huge variety. As we have seen, luck plays a massive part in the way life operates. The dinosaurs had bad luck 65 million years ago when that meteor struck the earth: for mammals, and for one particular species of mammal, it was the break they needed. Luck is more important than innate superiority. Mud dragons don’t look like conquering the world, though you can never tell; no one would have bet on us mammals either. Besides, in the lottery of life it is honour enough to survive.

  Pocket dynamo

  My experience of marsupials has been limited to what I’ve managed to pick up in bars. I once experienced two species together in a bar in Brisbane. The first was the thylacine, or Tasmanian tiger. It’s extinct now, alas, but you can still see it on the label of the excellent Cascade beer of Tasmania. The second was a possum. The waiter went to the garden to throw out some peanuts: a possum descended the tree, took them from his hand and accepted strokes. Naturally, I had to join in. A half-grown possum was riding jockey-style on its mother’s back: it had no interest in peanuts and was unwilling to be stroked, but the mother was very agreeable.

  Which shows something of how tenacious and how successful marsupials can be: hanging on as urban bandits despite the brutal concreting of their environment. We tend to see marsupials as freaks and aberrations: perhaps that was why I found the idea of marsupials so thrilling at my junior school. I remember doing a project about Australia and its marsupials precisely because they seemed, in so many ways, to be so remote from Streatham, w
here I grew up. There are getting on for 350 species of marsupials currently recognised, and 70 per cent of them can be found in Australia and New Guinea. The rest are in the Americas, mostly South America. There are 13 in Central America and one, the Virginia or common opossum, spreads as far north as the United States.

  We humans are placental mammals: all us placentals give birth to young in varying degrees of good-to-go-ness. We do a good deal of growing and developing inside the womb. Marsupials give birth to blobs which they raise outside the womb: in the famous marsupial pouch. A baby koala weighs one-fiftieth of an ounce: a bare scrap of almost nothing.

  These slug-like, utterly unmammalian-looking things are a little repulsive, in both the appearance and the idea. Sure, it’s only what we placental mammals do inside the womb, but doing it outside seems indecent. Partly as a result of this, we are inclined to be just a little patronising about marsupials, looking on them as exotic primitives, mammals that tried to reach the dizzy heights set by us placentals but fell woefully short. As is often the case, these stock human responses to the natural world tell us more about our own nature – our desire for both separateness and superiority – than they do about the animals themselves. A female kangaroo is able to cope with three young at the same time, all in different stages of development; not many placentals can claim that, least of all those the size of a kangaroo. Humans are exceptional in their ability to do so.

  There are marsupial equivalents of many of the placental mammals. The thylacine on my beer bottle was as cool a carnivore as any that you’d find among the official family of Carnivora. It went extinct because it got a taste for sheep when the white settlers introduced them, and was shot out.I There are gliding marsupials, as we have seen, burrowing marsupials who live as moles, and ant-eating marsupials. There is an extinct marsupial not unlike a rhinoceros, and another kangaroo-like marsupial with a neck like a giraffe. Another species was considered a marsupial lion, though some people now argue that it was a tree-climber and used its impressive teeth to eat fruit.