by Simon Barnes
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Oh fuck, another phylum. It’s probably the most famous remark made by the palaeontologist Simon Conway Morris, and no doubt the one he most regrets. All the same, I expect we can all empathise with it as we meet the phylum of Gastrotricha: the hairy-backs. Conway Morris was widely celebrated for his work on a fabulous collection of Cambrian fossils found in a rock formation called the Burgess Shale. Stephen Jay Gould, met before in these pages, made a hero of Conway Morris, and suggested that his discoveries demonstrated that Cambrian life was actually more diverse than the life of the present day. Conway Morris’sI remark was a reflection of the astonishing hyper-diversity of the Burgess Shale fauna. However, he disagreed with Gould’s conclusions, and suggested that most of the fossils could be properly accommodated in the modern phyla;II a view that is current orthodoxy.
It has to be admitted that the modern phyla don’t seem to be a particularly limited bunch, and that the more you look for life – even on the huge scale of the phylum – the more you find. Or to put that another way: oh fuck, here are the gastrotrichs. Bring on the hairy-backs.
They are astonishingly numerous, that’s the real point of them. They have been found at a density of 150 individuals in 10 square centimetres, say, 4 square inches, of water. Microscopic, then, found in marine and fresh waters, and most likely to found in between particles of sediment. They are also found in the film of water around grains of soil. Small things, things almost meaningless to the human mind, they are nonetheless, by virtue of their numbers, an important link in the food chain that sustains us all: feeding on impossibly minute scraps of life like microalgae and bacteria, and in turn preyed upon. There are over 700 species described, and they come in two main groups: strap-shaped hairy-backs and tenpin-shaped hairy-backs.
I have not, I suspect, thrilled my reader very deeply with this chapter. I haven’t sold the gastrotrichs over-well. And yet there they are, millions and millions and untold billions of them. So many: would the world be able to carry on without them? Would the world be very different if they didn’t exist? I suspect it would.
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I. Conway Morris is both a Darwinian and a Christian, and has given lectures to make the point that the two are not incompatible. Christianity does not require its adherents to accept creationism, and science does not require scientists or anyone else to reject religion. Here he is in agreement with Gould. Gould was not religious, but wrote that science and religion were not mutually exclusive. He coined the rather orotund phrase – he was increasingly prone to such phrases in his later work – of “non-overlapping magisteria”. Briefly, science can demonstrate the truth of Darwin’s theories, but science cannot, by its nature, have a view on the question of whether or not a human has an immortal soul. It is not science’s job to legislate on matters of belief. Such things cannot be proved or disproved and are matters of faith. Science does not deal in such things: they are not the business of science. In other words, it is impertinent for a scientist to lecture us on the non-existence of God as it is for a vicar to lecture us on the falsity of evolution.
II. Conway Morris named one Burgess Shale creature Hallucigenia, so bizarre did it look. Gould believed that it was not related to any living creature; the modern consensus is that it is related to the arthropods, the great group (we shall come to it eventually) that includes insects, spiders and crustaceans.
Look, no stabilisers
I have flown with eagles. I have to admit, though, that I was very frightened before take-off. It was the instruction to empty my trouser pockets that did it: to leave the Swiss Army knife and the pocket magnifier and the small coins behind, lest they work their way loose in flight and crash into the prop and break the damn thing. The prop, you see, was basically sticking out of my arse. Must be pretty fragile if you can break it with a 10p coin. That instruction rather underlined the fragility of the whole business of being up in the air. Humans aren’t really meant to do it. It’s against nature.
John Coppinger is an old friend; he runs Tafika Camp in (you’ve guessed it) the Luangwa Valley. And he has a microlight: one of those Heath-Robinson aircraft that is a strange coupling of kite and lawnmower engine. John sits in the front and holds a bar attached to the wing, which is nothing more than a triangle of fabric above his head. You ride pillion and hold onto – well, nothing much, actually. My old friend Chris Breen (the one who attended the death of the elephant), alarmed when John had gained some serious height, confessed that he was once reduced to clutching hold of the pilot. You rest your feet on things like aluminium cigar tubes.
The first time I went up, I took my place with the copper taste of nausea in my mouth. This feeling lasted all through the flight preparations and the run and bounce down the brief baked-earth runway. It vanished the instant, but the very instant, we left the ground. All at once there was the mad river beneath me, thrashing about from one side of the valley to the other like a wounded snake, as it has done for countless millennia. Down there I could see the vast mammals, now perfectly accustomed to the noise periodically made by the little aircraft: elephant, eland, impala, puku. We could visit the crowned cranes on their breeding grounds, in the soft swamps where no human can tread.
And we flew with the bateleurs. The bateleur eagleI is the great emblematic bird of the Luangwa Valley. They can be seen over most open savannah country in Africa, but they are or seem to be especially numerous in the valley. They hold their wings in a sharp V, a marked dihedral, to use the correct term from aerodynamics. This gives added stability in the roll axis. The birds are still not completely stable, and they need to make constant small corrections and counter-corrections. The word bateleur is French, and means a tumbler, a showman, a circus performer. This bateleur is a tightrope walker, tiptoeing his way across the sky with insolent ease, knowing that the air is his servant, not his master, and that gravity is in pretty much the same situation.
Flight is the birds’ great advance over the rest of the vertebrates: only bats can rival them for powered flight, and they are not all that close when it comes to comparisons based on pure flight. Sonar is a great trick and bats are masters at it, but when it comes to flying, birds are on a different level.
Flight is the birds’ evolutionary triumph, whether you are a ground bird that leaps effortfully into the air (like a peacock) at the approach of a predator, whether you are a small bird of the forest canopy that has forgotten that the ground ever existed, or whether you are a bateleur whose days are spent riding the air and, very occasionally, flapping. A bateleur will spend eight or nine hours a day in the air, and will cover an area of around 250 square miles, 650 square kilometres. It does this with a minimal expenditure of energy. Flight is very expensive, but gliding is highly economical: you just sit there and let the wind do the work. A bateleur will soar on thermals, rising columns of heated air, and will hoard the height like a miser, relinquishing it grudgingly as it cruises across the valley in search of food: pigeons, sandgrouse, snakes.
And here’s a rum thing: the bird seems to have no tail whatsoever. The red feet extend beyond the base of the truncated tail. The flight silhouette is so singular that it’s a standard tease to tell first-time visitors that “this is the only bird in the world that flies backwards”.II Tail-less flight is supremely efficient for all day gliding: less drag from the tail means that the bird loses very little height as it travels forward under gravity. But the technicalities of tail-less flight are hard to master, and that’s why a subadult bateleur doesn’t look much like a bateleur. Instead of being boldly picked out in black and white with a startling red beak and legs, this younger eagle is all shades of brown, and it has a tail. For the first seven or eight years of its life, it has a tail much in the manner that children have stabilisers on their bikes. The difference is that the tail doesn’t get removed all in one brave decision: rather, it diminishes as the bird shifts through its plumage phases. The young eagle has to learn how to be a bateleur. Mastery of the airways doesn’t come cheap: it
’s a long, hard education. Flight is a life skill that must be acquired and worked on. The adult bateleur’s casual confidence comes from a ritual 10,000 hours.
Flight is what birds excel at. You can choose many species – practically any species – to spell out this mastery: the daily miracle of the bateleur will do as a starting point. There are other birds with greater speed, greater drama, greater endurance, greater range and at least equal aerial skill, and we will touch on a good few of them as we continue our circling journey through the vertebrates. I remember looking down from the microlight, looking past my own left boot, at a bateleur who was flying his own flight without needing to make a horrible noise, with no need for an arse-shaving prop, out-turning us with the subtlest shift of those perfect aerofoil surfaces. The bateleur stands for the perfectly insolent nature of the birds’ conquest of the air. The bateleur is the bird that knows the sky loves him.
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I. To be strictly accurate, bateleurs are not true eagles, like the golden eagle and the bald eagle. They have no trousers: no feathery covering on the upper legs. They are classified in a separate but related group called snake eagles.
II. Hummingbirds really can fly backwards, and we’ll come to them in due course.
The crypto-bums
Entoproct means “anus inside”. And that is perhaps the most fascinating things about this phylum: they are creatures with hidden bottoms. They are quite easy to overlook – the entire creature, I mean, not just their bottoms. The biggest of them measures around 7 mm, 0.28 inches. They are goblet-shaped, so they are sometimes called goblet worms, for all that they are not a lot like worms. They have also been called nodding heads.
They are found in water; all but two of the 150 species described live in the sea. They have a crown of tentacles around the rim of the goblet, and they use beating cilia to encourage particles of food in the general direction of their mouths. I know you’ve heard that one before: it’s a very popular way of making a living. So many creatures, all of them clearly and sometimes spectacularly unrelated, have come up with the same basic solution to life’s first problem of getting enough to eat: just hang about and wait to see what the sky will drop in the way of food, and help it on its way by sort of beckoning to it. It’s a way of living that prompts two more or less simultaneous thoughts. The first is that a completely stationary lifestyle seems unnatural to us humans, but as we have seen, many, many creatures across many different phyla find it suits them perfectly. It’s not as if hanging about all day and all night in the same place is energy-expensive: and the business of making a living is based on balancing the books. If you rampage about all day and/or all night like a hyena or a bateleur, or if you are an insanely active shrew, you need to take on a fair bit of nourishment to keep going. A shrew will famously eat his own body weight in a day. Finding food tends to be an expensive business for birds and mammals: they need a lot of food in order to be able to search for food. But if you are an entoproct, hanging about and doing the occasional bit of wafting, you can exist on much less.
The second thought is that even granted all this stuff about the economics of survival, there must still be an awful lot of floating, drifting, tumbling bits of nutrition in the water, in certain places, to support all these waiters and hopers and wafters. The larvae of the entoprocts are free-swimming, but then they settle down, in the most final sense of the term, to grown-up life, swivelling through 180 degrees and turning both mouth and anus upwards. They can propagate by cloning, but they also do sex. They tend to start off as simultaneous hermaphrodites but some species later divvy up into sexes. And that’s it: wafting goblets with secret bottoms: creatures who have as fully evolved and effective a way of life as the president of the United States.
Same bat time, same bat hawk
Let’s look at some of my greatest bird-of-prey moments. Why not? They include many of my best moments for all wildlife. Or all life, for that matter. Looking down on a lammergeier cruising along a Spanish valley, being almost knocked off my horse by a hunting sparrowhawk, the marsh harrier on my honeymoon,I the hobby that stooped on a flock of house martins by a church in Barnet,II the hawk migration in Michigan,III the majesty of martial eagle, the daintiness of a merlin perched on my naked fist,IV the sheer speed of a peregrine… but I could go on forever and before long I would be showing off rather than explaining the wonders of the wild world.
The drama of them. Let’s have a bat hawk. Few animals on earth do drama quite as a bat hawk does. They are African birds that have cracked a specialist niche. As a result, they are busy for just a few minutes every day: but those few minutes are spectacular. At dawn, and especially at dusk, a bat hawk turns from a small black statue into a high-speed high-stealth killing machine. As the bats come out to feed at the end of the day, and as the bats return home in the fore-dawn, so the bat hawk preys. And that’s how you see them: as a silent clap of thunder. An expanse of still water is best, for you have a clear view and plenty of ambient light. There are also many insects associated with the water, and they bring in the insect-eating bats. It’s the moment when the sight-hunting tactics of the hawk and the echo-locating techniques of the bat overlap, and it’s the bat that tends to pay the price. Out of a dark sky, the darker bat hawk will strike: the shadow of a shadow: appearing in your vision for about two seconds before vanishing… leaving an indelible memory on every human tuned into such things. Remember when we saw the bat hawk? You mean the one by the lagoon at Nsolo? I’ll say I do.
Birds of prey have a deep and rich meaning for humans. They are all of them glorious: and that’s because they have to be. Their way of life is intensely demanding: therefore they are right on the limits of evolutionary possibility. They have to be able to stay in the air all day like a bateleur; or they have to be as swift and as secretive as a bat hawk, or they have to be as fast as a peregrine or as manoeuvrable as a sparrowhawk. They have no choice. For a bird of prey, perfection is the only option. That is, in fact, a kind of heresy: as said before in these pages, evolution is not about seeking perfection, it’s about finding a solution to the questions that life asks. All the same, birds of prey look very much like perfection: and it’s probably fair to say that they are as perfect as anything that evolution has come up with. To human eyes, they are an embodiment of everything that we find awe-inspiring in the wild world.
The notion of “birds of prey” is a fairly rough-and-ready concept. Plenty of birds kill and consume their fellow vertebrates and are not counted as birds of prey: an osprey preys on fish and is a bird of prey while a heron does the same thing and is nothing of the kind. Skuas, penguins, storks and kookaburras, to name but a few, are predatory birds that are not birds of prey. The tendency is to lump together five more or less related groups of fierce birds and call them “diurnal birds of prey”. They all have superb eyesight, claws specialised for grasping and killing, and a butcher’s hook for a beak. It’s wiser not to speak of “nocturnal birds of prey”; these are more frequently referred to as “owls”, and we’ll have a look at them in the chapter after next.
These diurnal birds of prey are almost all fabulous fliers, but they have many different kinds of different kinds of fabulosity. The marsh harrier I can observe from the window of my study as I look out over a stretch of marsh is very good indeed at flying extremely slowly: quartering a feeding ground at speed that would cause many birds to stall and fall out of the air. Slowness gives it time to survey with immense precision: the better to examine what is below and when the moment is right, kill it and eat it.
The peregrine goes for the opposite strategy and is the fastest bird in the world. A peregrine, streamlined, powerfully muscled and with swept-back wings like a fighter plane, is capable of reaching 60 mph, 100 kph, in straight and level flight: only a few birds can match or perhaps beat this, some waders, ducks and pigeons. A swift, the white-throated needletail, has been clocked at 69.3 mph, 111.6 kph. But in a stoop – a thunderbolt attack on a flying bird, plunging from a height and s
o exploiting gravity to add to its speed – the peregrine doesn’t so much speed up as pass into another reality, reaching 200 mph, 322 kph. Even at such speed the bird has enough control to home in on a flying bird, one that is manoeuvring in three dimensions and often enough, attempting to escape – though plenty are caught completely unawares.
The techniques of all-day gliding and soaringV are practised by vultures of both the old and the new world. These two groups are not, in fact, closely related but they are both adept scavengers. The new-world birds, which include the famous condors, have, unusually in birds, a sense of smell. The sparrowhawk is a hider and ambusher, the greatest of all sneak-strikers, with almost impossible manoeuvrability. I have seen a sparrowhawk fly at full speed though a wood, going through gaps a blue tit would think twice about, folding its wings and unfolding them on the far side of the gap to emerge and strike at unsuspecting birds on the other side, often inverting in the air to stretch out a single foot armed with killing claws. The osprey is in a group by itself: the dashing fisher that is found all over the world.
And one oddity. The secretary bird is a bird of prey that hunts on foot, stalking about the open plains of Africa apparently with its hands behind its back, in the same terribly interested fashion of Prince Philip reviewing the troops. It specialises in taking snakes from the ground.
Birds of prey have a special meaning for humans: often a bellicose and hyper-masculine one. Best not to explain, perhaps, that among birds of prey, the female is almost always larger and stronger than the male and capable of dealing with bigger prey. Birds of prey are the birds men would like to be: in America’s National Football League, three of the 32 teams are named for birds of prey: Philadelphia Eagles, Atlanta Falcons and Seattle Seahawks. Birds of prey are the most admired birds on the planet: and they are also the most persecuted. The illegal killing of birds of prey is one of the most intractable problems of conservation. In England, only one pair of hen harriers succeeded in breeding in 2012, despite the fact that there is capacity for more than 300; the following year not a single pair bred. The problem is that most hen harrier habitat is on grouse moors that are managed for shooting. A satellite-tagged bird, Bowland Betty, was shot a few weeks after she was tagged. When it comes to perfectibility, we humans time and again succeed in bringing off the perfect contradiction, particularly when it comes to our relationship with the wild world, which we love and hate in equal measure.
