Ten Million Aliens

by Simon Barnes

  So much is common to all rodents. The disparity between species is equally remarkable. Rodents live underground, on the ground and in tree canopies never touching the ground. They can live in deserts and never take a drink, they can live in water, or semi-aquatically at any rate, and some species have webbed toes to help them do so. They can be found on every continent, including the Antarctic, because some species have grown adept at living off and alongside humans. Rodents have been found living in cold-stores – not just raiding, but living full-time inside them – and at the bottom of mines. They include – to take a lightning and rather selective run through the order of rodents – beavers, capybaras, flying squirrels, non-flying squirrels, dormice, voles, chipmunks, mice, rats, porcupines, chinchillas, guinea pigs and coypus.

  They usually have a pretty small body size: the African pygmy mouse is 6 cm, 2.4 inches, long without the tail, though the Baluchistan pygmy jerboa can be even smaller. The biggest is the capybara: a majestic giant guinea pig. I have walked among a gathering of them in a public park in Curitiba, in Brazil; I felt like Alice after she had drunk from the bottle that said Drink Me and shrunk drastically, as I strolled thigh-high through guinea pigs. Capybara can reach 65 kilos, and an exceptional animal weighed 91 kilos. But these are midgets compared to some of the extinct species of rodent: Josephoartigasia monesi was, it has been estimated, capable of reaching 1,000 kilos, 2,200 pounds or more.

  Rodents are mostly compact and short-legged, but where there is an absence of antelope competition in South America, you find long-legged, rangy rodents like agoutis, maras and pacas. Rodents don’t have the complex ruminant stomach that antelopes possess, which allows them to digest cellulose and so get enough nutrition from grass. But rodents who specialise in eating greenery manage the same trick by passing it through their system twice: that is to say, they eat their own droppings. The second time through, the droppings are hard and unpalatable. Rabbits (not rodents) do the same, which is how they function so effectively as grazers: if you have read Watership Down and wondered what Richard Adams meant when Hazel and Fiver were relaxing in their burrow “chewing pellets”, you need wonder no longer.

  Rodents have other advantages that have contributed to their extraordinary success. They are small, and they have a rapid breeding cycle. In optimal circumstances, they can reproduce at a rate that pest-control people love to scare us with: six mice in a house can become 60 in three months; one female can produce up to ten litters a year, each of a half-dozen young, all of whom could be breeding within 30 days.

  Humans tend to hate mice because they invade our homes and eat our food and foul our cupboards and lofts and damage the places where we have our being. Perhaps it is helpful to think of humans as mice and the natural world as the home of others species: a home that we invade and foul and damage. We are probably more capable than mice of making a moral choice: pity we don’t do so all that often.

  Tipping the velvet worm

  A woman walked into a bar and asked for a euphemism. So I gave her one.

  Rather a favourite joke of mine, that, and it came to mind with the requirement to write a chapter on velvet worms. No doubt it got there at least partly because of a 1998 historical novel about a lesbian love affair. It was called Tipping the Velvet, apparently a Victorian euphemism for cunnilingus; the book was made into a television series.I

  But both velvet and worms have long been used in sexual codes, so you’d be entitled to think that a velvet worm chapter was an elaborate practical joke, if not a rather diseased and unhealthy fantasy of the author. Nothing of the kind, I assure you. Velvet worm is the common name for the phylum of Onychophora, which means claw-bearers. It’s not one of your big phyla, no more than a couple of hundred species described, but they are related to the biggest of them all, the arthropods, which we’ll come to in due course. It has been speculated that velvet worms are relict ancestral arthropods, so you can look on them as both a failure and the greatest success in the Animal Kingdom. Water bears, incidentally, are also related to arthropods. Rum the way it all works: the same branch of evolution produced these two obscure phyla which between them have only a quarter of the species of us mammals, and we’re not even a full phylum. But the third turning on the same branch provided the arthropods: and practically every living species of animal is an arthropod.

  It’s not exactly a question of where did it all go wrong, as the bell-hop so famously asked George Best.II It’s more a demonstration of the truth that one basic design is more suitable than others when it comes to producing endless forms. It’s a nonsense to speak of dead ends, or of failed experiments. Velvet worms, like water bears, are viable and effective animals. It’s just that they’re not very various, or for that matter, numerous. They work, though: and that’s enough to be going on with. Life is not about being ambitious; it’s about continuation, and velvet worms continue.

  So far as humans are concerned, velvet worms have their being in obscurity: making a life in leaf litter and crevices in warm parts of the world, especially rainforest, in the Americas, Australia and Africa. They are mostly nocturnal, though they are often active after rainfall. They are hard to spot: you are unlikely to find yourself out in the forest with a guide keen to show you his velvet worm.

  They look like caterpillars; some more like giant caterpillars. They have bodies a little like earthworms, but with stumpy legs that make them look a little like millipedes, though they are related to neither. They are, to use a delightful phrase, “obscurely segmented”; in other words, their body is divided into segments (like insects and other arthropods, in fact) but the segments are quite difficult to make out. This is because they are not rigid animals; they are kept firm by their fluid content. They can dry out in adverse conditions, like other non-related creatures such as worms and sea anemones. They need high humidity in order to be safe, which makes rainforests an immensely suitable place for them. They stretch and contract their bodies in order to move, and they do so on stubbly little feet with the pleasant name of lobopods. They can be anything from half a centimetre to 20 cm, a quarter-inch to eight inches. Most of them are reddy-browny in colour, but there are some decorative ones in bright green, blue, gold and white, and some are patterned. They move in a slow and graceful fashion as if they were doing an invertebrate form of tai-chi, which makes it hard for predators to find them; most predators’ eyes are tuned to catch movement. All the same, velvet worms are highly effective ambush predators, and they use a single terrible weapon: slime.

  Their basic strategy is to lie in wait for a small creature and then to slime them. They can squirt this as much as 4 cm, nearly 2 inches. This slime is good stuff: high tensile strength and great stretchiness. They make a net of slime, which they use gladitorially.III They will eat and recycle dried slime; it’s expensive stuff to produce and it takes 24 days for them to reload.

  There are few groups of animals, and for that matter, few individual species, that don’t challenge our human preconceptions. Velvet worms have a social life; groups of up to 15 individuals have been found together. It is presumed that these are related animals. They have been seen hunting cooperatively; some more conservative anthropologists still suggest that cooperative hunting was a human invention. These colonies or family groups tend to be aggressive to other velvet worms that invade their sanctuaries, which are often under a good log. When a kill has been made the dominant female feeds first. They eat woodlice, termites, crickets, cockroaches, millipedes, centipedes, spiders (they will first slime a spider’s fangs), worms and even snails.

  There is one parthenogeneticIV species, but most have a sex life, if not a terribly thrilling one. Females tend to be larger than males, with more legs. The male produces sperm and makes a bundle of it, which he then trowels into the female’s genetic opening; some species use a dagger-like or axe-like structure on the head. There are two species that simply slap the sperm-packet onto the female’s flanks. From there it is absorbed, though not without causing skin injury. Most
velvet worms live at low density. Obscurity is their chosen method in life, and in a quiet and unlooked-for way, it works as well as most other strategies.

  * * *

  I. Such matters are (a) more acceptable and (b) more titillating in period costume.

  II. Apologies if this ancient footballing story is unfamiliar. The incident took place after Best had retired from football. On the day in question he had taken to a hotel bedroom after a sizeable win at a casino. The room was full of fivers and a lovely lady, usually described as Miss World.

  III. Secutor versus retiarius: swordsman against the man with net and trident; odds three to one in favour of the net-man.

  IV. Going in for virgin birth.

  Dirty rats

  There is no better way of looking hard-nosed than to embrace a misunderstanding of Darwin. Hitler is but one example. People who have reservations about wildlife conservation will tell you that the endangered animals are losers:I weaklings: evolutionary failures. Humans have taken over the planet: deal with it or go extinct. Those that fall by the wayside – pandas, tigers, rhinos – well, sad, but that’s life. Or not, of course. Either you learn to adapt to humans or you fail: some writers have taken up the term Anthropocene: a new geological era created by the planet’s dominant species. But we humans have always allowed ourselves the luxury of entertaining two contradictory ideas at the same time; in fact, it’s the founding principle of human civilisation. So we can despise the animals that fail to adapt to the human domination of the planet – and at the same time, we can despise the animals that have adapted to humans and live alongside us in profusion. Seagulls that haunt landfill sites, pigeons that fly around city centres, cockroaches in our kitchens: all these we treat with contempt. But when it comes to fear and loathing, nothing beats a rat.

  The brown rat, Rattus norvegicus, is one of the great success stories of the last millennium. Not known in Britain before the 11th century, it has become a seldom-seen omnipresent fact of city and country life. In a city, you are never more than 3 metres or 10 feet from a rat, so they say: information designed to make our flesh creep. There are more rats than people in Britain, There are supposed to be 100 million rats in New York. We despise rats as scavengers: the more polite and scientific term is commensals, creatures that share the table with humans. But the idea of rats at the table is not overly appealing, so perhaps I’d better drop it.

  The muroid or mouse-like rodents have been the triumph of the triumphant rodents, with around 542 species. They are marked by an ability to survive, multiply and adapt quickly to changing circumstances. Rats are the triumph of the muroids. In Graham Greene’s novel Travels with My Aunt, Mr Visconti, Aunt Augusta’s lover of all lovers, war criminal, con-man, thief and so forth, says: “I have a great fellow-feeling for rats. The future of the world lies with the rat… Rats are highly intelligent creatures. If we want to find out anything new about the human body we experiment on rats. Rats are ahead of us indisputably in one respect – they live underground. We only began to live underground during the last war. Rats have understood the dangers of surface life for thousands of years. When the atom bomb falls the rats will survive. What a wonderful empty world it will be for them, though I hope they will be wise enough to stay below. I can imagine them evolving very quickly. I hope they don’t repeat our mistake and invent the wheel.”

  The brown rat is a wet-loving burrower, and over the course of the last millennium, it has mostly displaced the black rat, Rattus rattus, which is a climber by nature. The brown rat, spreading from Scandinavia as the scientific name implies (though both species have their ultimate origin in Asia), out-competed the black and sailed to the new world. Rats are a fact of life: an ineluctable aspect of the human condition. I live in the country and keep horses and chickens: naturally, I have rats. They take feed and they pollute feed and they damage stuff, and what’s more, they are the cause of ill-feeling among neighbours: so naturally – or unnaturally if you prefer – I control them. Which is a euphemism for killing them: Andy, the rat-man, who used to play darts for Suffolk, baits for them – which is a euphemism for poisons them – and makes sure that numbers don’t get out of control.

  Control! That’s an important part of it, of course. When you read a newspaper scare story related to wildlife, you generally learn that numbers are “out of control”. Why is there a need for wild species to be under human control? That’s never explained. The idea of losing control, of being unable to regulate the numbers of wild animals we have around us, is something that profoundly distresses us modern humans. It is an insult to our omnipotence, a serious challenge to our understanding of ourselves and our place on the planet. We humans define ourselves by our control – and yet there is a contradiction within 10 feet of you, if you are reading these words in a city. We are not in control. We may be able to extirpate a lot of species with great efficiency, both on purpose and by accident, but there are some species that we simply can’t control, no matter how hard we try. They are just too good for us: too smart, too well adapted, too effective. Andy keeps rat numbers down: it’s the best he can do. If he ever succeeded in wiping out all my rats, he would only create a vacancy, one that would soon be filled by incoming rats from all over the village. Rats are terrifically effective.

  They often carry fleas. The oriental rat flea is the vector for the pathogen Yersina pestis, which causes bubonic plague. Rats are not the sole host, but they bear the blame for the pandemics that changed the course of global history, with the Justinian Plague of the 5th century AD, the Black Death of the 14th century and the Great Plague of London in 1665–66. There were 18th-century outbreaks of plague in Marseilles, Cadiz, Messina and Russia. There was a pandemic in China and India from 1855 until, according to the World Health Organisation, 1959. There was plague in Algeria in 2003 and in the Congo three years later. Human history has been shaped by fleas, though we prefer to blame the rats that bore them: you’re the dirty rat that killed my civilisation.

  Western civilisation has never had many good things to say about rats, for all that they have been roped into thousands of scientific experiments for the very good reason that rats can tell us an awful lot about human beings. But some cultures are less single-minded in their detestation of rats. A rat is the vehicle of the beloved elephant-headed Hindu god Ganesh. I have visited a Jain temple in which the rats were not only fed but honoured. In some Indian cultures, rat meat is considered a delicacy.II In the Chinese horoscope, the year of the rat is by no means inauspicious; its natives are said to be creative, intelligent, generous, honest, ambitious, quick-tempered and wasteful. There is a fine statue commemorating a rat with such qualities in Kyoto; you can find it if you walk the Philosopher’s Walk, a stroll that takes you past a number of Zen temples. It is a walk devised for contemplation of higher things than species hatred. What’s to hate about rats anyway? Sure, they’re ubiquitous, destructive, rapacious and far too effective at breeding. But as you stroll along the Philosopher’s Walk, you are entitled to ask yourself: well, who isn’t?

  * * *

  I. It’s an interesting philosophical point. The current wave of extinctions is the work of humans, mostly because we have changed conditions – moved the goalposts of evolution, if you like – faster than natural selection can cope. Is it our moral duty to consider non-human animals and amend our ways? Is it in our own best interests to look after the planet we live on? Is it better for our souls, for our sense of well-being, our sense of being at home on this planet, to cherish wild places and the creatures that live in them? Or is it humans first and damn the rest?

  II. The novelist Anthony Burgess claimed more than once (he was immensely keen on recycling) to have eaten rat stew in Chinese-run ships, praising the excellence of their flesh fed from grain they scavenged in the holds, and stressing that their diet made them far more esculent (favourite Burgess word) than rats who lived in sewers.

  Another can of worms

  When we think of worms, we usually mean the segmented
worms, the annelids. They are, to the human mind, proper worms, worms that understand what we expect of a worm. We’ve already looked at flatworms, velvet worms and nematode worms, which are all as separate from each other as they are from humans, all of us in our separate phyla. The segmented worms take the whole thing a step further, and they offer us around 17,000 species in more than 130 families. A number of minor phyla have been downgraded and tidied up into the phylum of annelid worms, as if for administrative convenience, but in fact, it was because of the latest bout of revisionism in the taxonomist’s art. The annelid worms include earthworms, ragworms (including those dug up as bait for fishermen), bristleworms and leeches. Have you ever looked out over a river estuary in winter when the tide is low? You will see acre upon acre of soft, fine, beautiful mud, peopled and patrolled by waders beyond counting, birds all prodding their beaks into it. So many of them: and all of them dependent for their lives on annelid worms. If there are that many predators, how many prey animals must there be down there in the wet, salty, fine-grained gloop? Annelid worms live in salt and fresh water and in damp terrestrial habitats. They fill all kinds of habitats in the sea, from the intertidal zones down to hydrothermal vents.

  It’s worth taking a moment to consider these vents. We used to accept the notion that every food chain on earth begins with the sun. But this bleeding-obvious idea was contradicted by the discovery in the last century of communities that make their living around hydrothermal vents: undersea places fuelled by volcanic energy, like marine versions of geysers, fumaroles and hot springs. These places can support life at up to 100,000 times the density of the surrounding seabed, and they do so without any (direct) reference to the sun. The giant tube worm is a dramatic member of this community. The worm anchors itself with its body and extends a red plume to harbour the bacteria which gain their energy from the minerals that come from these vents. It’s an impressive creature, which can be up to 2.4 m, 7 feet 10 inches long.