"Little Creatures Who Run the World"

PBS Airdate: August 12, 1997

ANNOUNCER: Tonight on NOVA, humans may think they run the world, but there is another superpower who is really on top. They outnumber us a million to one. And little can stand in their way. Their engineers breach wide gaps in a single bound. Their workers lift weight twice their size. Their soldiers are studied by U.S. defense analysts. Who is this superpower, and what makes them so successful? NOVA gets up close and personal with the "Little Creatures Who Run the World."

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BILL MASON: We humans like to think that we run the world. But even in the heart of our great cities, a rival superpower thrives: the ants. These tiny creatures live all around us in vast numbers, though we hardly even notice them. But in many ways, it is they who really run the show. When ants march together, little can stand in their way. Some ten thousand types are known. They outnumber us a million to one, and the total weight of ants matches that of the entire human race. But could these insect societies really have the edge on us? One man believes that they might: Professor Edward Wilson of Harvard University. His provocative insights on the social nature of both ants and humans provide a new understanding of what leads to biological success. And it's the insect societies that impress him the most.

EDWARD O. WILSON: I've spent most of my life working on tiny insects like these leafcutter ants—Each one is only about a millionth the size of a human being—and over the years, I've become convinced that the key to their success is, quite simply, the way they work together. To see why that's true, we can go almost anywhere in the world on the land, or back to almost any point in time. So, let's go way back, to the beginnings of this success story.

BILL MASON: The first insects emerged during the age of coal, some three hundred million years ago, long before the dinosaurs appeared. The ancient swamps were their kingdom. With no birds to compete with, dragonflies ruled the air. A few were giants, with three-foot wingspans, but only smaller forms survived. Other insects were to succeed them as the premier force. On land, cockroaches thrived. Their line was to persist and multiply. Around a hundred million years later, dinosaurs stalked the land, and a new insect power was emerging. The first wasps worked alone to dig simple nests, but for them, a social revolution was looming. They captured other insects to feed their young. These family bonds gave their line an edge, and the wasps gave rise to the prolific ants. But rival forces were gathering, hidden away in rotting wood. Simple societies of cockroaches began to multiply. Living in family groups was the key to their success. They feasted on decaying wood, but could only digest it with an internal soup of microscopic organisms. Youngsters inherited these vital organisms by feeding directly from their parents. The termites, or so-called white ants, rose from the same stock as the social roaches, and they would become the only rivals of the true ants for numbers and living space. By thirty million years ago, the dinosaurs were long gone. Birds were on the scene, alongside the surviving reptiles. And on land, the greatest insect force of all time was well-established: the fearsome ants. Descendants of the early wasps, they had shed their wings, but retained the powerful jaws and stings to become a major predatory force, outnumbering the remaining wasps by far. Their strength came not just from weaponry, but from working together. Living in close-knit colonies, the ants soon became the most abundant of all insects. Evidence for this ancient success story has come to light through a remarkable process. Sticky sap, oozing over tree bark, proved a fatal attraction, and many insects became trapped. Over millions of years, some of the sap became fossilized as amber, along with its prisoners. The earliest and most wasp-like of all known ants was suspended in sap a hundred million years ago, with every detail preserved.

EDWARD O. WILSON: So, the ants have been around a very long time. This is an actual specimen trapped in plant sap about thirty million years ago, turned into a beautiful fossil. And this is an ant that I just collected last year in Costa Rica. This two are so close together that they might as well be put in the same species. So, the ant way of life is very ancient and very successful. As far as human beings are concerned, we've been around for only one million years—too soon be sure.

BILL MASON: What is it about the ant way of life that has stood the test of time so well? All ants belong to extended families, and carry their prey home to share. Unselfishness is the rule. Everything they do is for their colony's good. Close relationships are the basis for their society, for all the active workers are sisters, spawned by a single queen, a larger ant who rules her subjects throughout her life. Some queens live for decades and lay millions of eggs. Workers rarely get to breed, and devote themselves like robot slaves to the colony, tending their youngest sisters, the helpless white grubs. Workers don't calculate the pros and cons of this life; their behavior is programmed. But raising lots of close sisters rather than struggling to breed alone ensures success, both for the colony and themselves. Workers clean the grubs obsessively, and fight off infections in their underground kingdoms with antiseptics from special glands. An ants' nest is like a Swiss watch. Complexity comes from many intricate parts doing separate, simple jobs, all with a clean and humming precision. Collecting food and tending eggs, grubs, and the cocoons of unhatched sisters are all vital chores in the colony's efficient production line. But the only products that count towards long term continuity are the winged males and future queens the colony rears, because the founding of new colonies depends on them. Thousands of young queens and males pour out of harvester ant nests in Arizona each year. On just a few evenings following the summer rains, all the colonies for miles around erupt at exactly the same time. As if at a given signal, they start to take off, encouraged by the workers. Tens of thousands gather, carpeting areas the size of football fields with their bodies. The males fan chemicals into the air to attract queens. And as each one arrives, a cluster of males scrambles to mate with her, for this is an ant orgy, and each male competes to pass on his colony's genes. Mated queens fly off to start new families, while exhausted males expire in drifts on the desert floor. But they've ensured the continuation of a line that goes back for millions of years.

EDWARD O. WILSON: The ants are not only long-lived, but they occur around the world in a tremendous variety of habitats. Even in the frozen forests of the north, there are ants. Nest mounds as high as six feet dominate the landscape, and each one is home to a million or more wood ants. These ancestral piles pass from one generation to the next, and some may date as far back as the nineteenth century.

BILL MASON: In winter, it can drop to minus forty degrees outside. But the ants survive huddled together inside. Toward the spring, the ants produce body heat which warms their homes and helps to melt the snow off the mounds. When the thaw is complete, the ants pour out to sunbathe before setting off to raid the forest like a hungry army. Their winter huddling gives them a head start on other insects, and force of numbers ensures few competitors get in their way. The shifting sands of the Sahara Desert, where surface temperatures reach a hundred and forty degrees Fahrenheit or more, are also home to ants. Desert ants are the only animals to brave the midday sun, and they hunt for other creatures that have died from the heat. They are known to navigate through this featureless landscape by scanning the sky at regular intervals to check the sun's position. They endure higher temperatures than any other land animal. But even they escape the burning surface when they can. These ants are suicidal. They die within a few days in this heat. But their missions are crucial. When they find food, they run straight home. Their colonies persist in one of the harshest places on Earth through navigational skill and heat tolerance, but above all, through the selfless devotion of the workers. But in Ed Wilson's view, tropical rainforests are the true kingdom of the ants. More kinds of plants and animals flourish in these cathedrals of life than anywhere else on Earth. But even here, social insects, especially the ants, rise above all the competition, and are by far the commonest creatures thriving in mind-boggling numbers. These forests have been a well of inspiration and discovery to Ed Wilson, and year after year, he has drawn back to untangle further mysteries.

EDWARD O. WILSON: A lot of people think that the forest is teeming with big animals—jaguars, monkeys, snakes, and so forth. They are there, and they certainly are appealing. They're exciting when you run across them. But you don't see them very often. They're very scarce. By far, the dominant creatures are the little animals—the insects, the spiders, and other arthropods that abound at every level in the forest. They're not easy to see if you just stand and look around. But when you probe a little, you see that they are there, in the greatest array and diversity that, I think, has ever evolved on the planet in the three and a half billion years of life's history.

BILL MASON: Much of this teeming life is concentrated high in the roof of the jungle. Scientists who have probed this high-rise world believe that over five million kinds of insects live here. But of all these creatures, the ants are the most prolific. They make up half the insects in the canopy, and a single tree may be home to nearly fifty types. The jungle floor, too, is crawling with life.

EDWARD O. WILSON: In that one handful of litter and soil is more order and richness and history than in all the planets in the solar system put together. If you dig down into the tangle of rootlets and bits of vegetable matter, you'll see a few ants and a termite or two. You'll see a whole host of springtails and little beetles and a lot of other creatures. It's a miniature wilderness. It would take lifetimes to completely explore. And if you magnify it still more, you'll come to microscopic mites, the little fanged creatures, and tufts of millions of strands of fungi. In just one gram of this material, you can find somewhere in the order of ten billion bacteria belonging to several thousand species, almost all of which are still unknown to science. Among the animals that are visible to the naked eye, the social insects completely dominate. If we were to take all the animals in this forest, from birds and snakes down to little insects and roundworms, we'd find that the ants and the termites make up about one third of the total weight. And I'd say that, within ten yards of where I'm sitting, we could expect to find a hundred or more species of ants and termites alone.

BILL MASON: So, on almost every count, success through geologic time, geographic range, and sheet weight of numbers, ants and other social insects come out ahead. But what gives them the edge over insects that go it alone? Ed Wilson has clearly shown that much of the answer lies in the way they coordinate their behavior through efficient communication.

EDWARD O. WILSON: The amazing thing is that they communicate mostly with chemicals, with substances that they pass back and forth, and taste and smell. I can communicate directly with the ants myself—these fire ants on the table—simply by taking an extract of the bodies of several of the workers, dipping this sharpened stick in, and laying a trail on the table for them to follow. And they'll go wherever I tell them. Each one of these fire ants has only a billionth of a gram—That's ten billionths of an ounce—of that substance in its body. And yet, the material is so powerful that a milligram of it is theoretically enough to lead a column of the ants three times around the world. Ants generally use between ten and twenty chemical signals of this kind to alert nestmates to danger, to lead them from one place to another, to identify the caste of their nestmates, and so on, through the whole bizarre vocabulary to keep the colony well-organized and efficient.

BILL MASON: The only insect superpowers to rival ants for numbers are the termites. And they too rely almost entirely on chemicals for communication. Descendants of wood-eating cockroaches rather than wasps, they've developed a complex family life much like the ants, with a huge queen tended by slave-like offspring who devote their lives to looking after her and her young. Ants and termites have been deadly enemies for a hundred million years, and much of their rivalry has been over living space. Ed Wilson considers that for both groups, togetherness is their greatest strength.

EDWARD O. WILSON: Here in the Trinidad rainforest, this strange-looking object is home to maybe a hundred thousand termites. It was built by a remarkable team effort, and the termites use the sheer strength of their numbers to defend it against their enemies. When I break into the nest like this, the first wave out are the soldiers. Each one of them has a nozzle-shaped head, from which it squirts a stream of noxious chemicals in a glue-like substance. Now, that stops most enemies cold, and if I back off, after a while, the soldiers will go back in. And then, the next caste comes out, the soft white workers. They bring up building material from inside the nest, and use it to patch over the hole. Colonies can survive heavy assaults on their nests because they're able to bring out large numbers of individuals who work co-operatively and very efficiently. Social insects like this generally do better than solitary insects also, because the individuals can afford to risk their lives, even give their lives away. If some of them die in the attack, no matter. They'll soon be replaced by newborn brothers and sisters inside the nest.

BILL MASON: Simple homes protect termites in the humid forests of the tropics. But they build huge fortresses in the harsher conditions of the Australian outback and the African bush. Termites build perhaps the most impressive homes of all animals. In some places, their mounds cover nearly a third of the land surface, and the total weight of termites can equal that of all the mammals in the area. Vast teams of tiny workers build twenty-foot skyscrapers. That's two miles high in human terms. But termites have their limitations. They eat only dead wood and other plant matter, although in huge amounts. But when it comes to killing, they are no match for the fearsome ants, who combine a harmonious homelife with a ruthless approach to their enemies. Columns of Kenyan raid ants set off in pursuit of termites, following a chemical trail laid down by scouts. The ants bunch together as they approach the termites' nest before pouring into their underground chambers. The raiders dump each victim on the surface before returning for more, while others begin to gather up the corpses. At the height of the raid, the surface is littered with dead termites. The raid ends as suddenly as it began, and the ants collect their booty and head home. Each ant carries up to ten termites in its jaws. They've killed over three thousand in the space of ten minutes, not enough to destroy the colony, for they'll need to come back another day. By combining force of numbers with organized aggression, ants have become the greatest insect killers on Earth. But all creatures have reason to fear one particular African ant, whose cavernous shafts descend six feet or more into the ground. These ants live in the biggest single colonies of any animal on Earth, with up to twenty million sisters operating like a huge monster with a monstrous appetite to match. These are driver ants. When they march, nothing in their path is safe. They've been known to kill tethered horses, human babies, and have even been used to execute criminals. Soldier ants stand guard over the marching column. The river of ants divides, spreading out over the forest floor. Few victims escape once the ants get a grip. Millions act like a fearsome super-organism emerging from its lair, sending out long tentacles of marching workers to engulf its prey. A giant slug seems an unlikely target, its thick slime a sticky trap. But the persistent ants overwhelm the slug. They have a neat trick to soak up the slime, sticking tiny fragments of leaf and soil all over the slug. The soldiers now get to work, slicing it up like a beached whale with their powerful jaws. The ants then release their trapped sisters. It's all for one and one for all. The relentless army marches on. Those that can, leap for safety, while others watch from above as hordes of cockroaches and other insects are driven ahead of the raid. Many that escape the ants run right into the path of shrikes and other birds that feast on fleeing insects. There's no safety in fleeing upwards, for the ants follow. A praying mantis is more than a match for just a few ants, but with so many attackers, it can't eat them fast enough. They carry the mantis off, piece by piece. Several ants share the heaviest loads. Workers labor to keep the trail clear. Soldiers form living archways over the columns, and hold back twigs and leaves. It's a genuine team effort. The ants return home, carrying their spoils deep underground, where millions of developing grubs are waiting to be fed. In ant society, no job is left undone for long, and back outside, yet another task force throws out the remains of past victims. Driver ants kills almost everything within range of their nests, and relocate from time to time to find enough food. With no fixed abode, wars between colonies are rare. But in the deserts of Arizona, warfare between ant superpowers is waged non-stop, for these ants have permanent homes, and their cellars are full of treasure. These grotesquely swollen creatures are honeypot ants, and they devote themselves to the colony as living storage pots. In times of plenty, their sisters fill them to bursting with nectar from desert blooms, and demand it back during lean, dry spells. The colony can live on these stores for weeks, but when the weather allows, they venture forth in search of prey. They check out hidden entrances and savage any juicy termites they find. Such a find is best kept in the family, and a scout, on meeting a stranger, runs back to its own nest. Reinforcements pour out to confront the opposition, while others continue to gather termites. Instead of launching straight into battle, these ants limit their losses by aggressive posturing. They square up to rivals, standing on tip-toe to seem as large as possible, while checking the others' size with their feelers. They recognize their sisters by odor, and separate immediately on meeting. They often climb up onto stones, perhaps to appear larger still, for one colony seems to judge another's strength by how many large workers show up. Colonies appear to remember show they fared in recent conflicts, and back off where they've lost before. But if they sense an advantage, they'll send all available forces into battle to drive their opponents back to their nests. As in human warfare, the worst routs occur when one side fails to assess the other's strength accurately. And when forces are poorly matched, posturing soon gives way to fighting, and the smaller colony is overrun. Tactical ant warfare has even attracted interest from defense analysts trying to sharpen up their methods of assessing enemy strength. The victorious ants raid their opponents' nest for the spoils of war, dragging off the struggling honeypots. Damaged honeypots are eaten, the rest forced into bondage, feeding their new masters on demand, a system uncomfortably reminiscent of human slavery. Wise use of military strength pays off for ants, but is force the only way?

EDWARD O. WILSON: Not all ants use violence to dominate their world. Some use more subtle methods to get their way. These particular ants are dairy farmers. They're gently looking after a group of tiny treehoppers, which is a kind of bug that sucks the juice of forest trees. These little creatures, living together in a bunch, offer the ants the excess they get in the form of honeydew droplets, a sweet-tasting liquid that's rich in sugar and amino acids. This kind of relationship has existed for millions of years, long before human beings ever started tending cattle, and some of the connections have become intimately close, as close and ingenious as anything ever devised by human culture. Take, for example, the true herdsman ants of the Malaysian rainforest.

BILL MASON: These ants get all their food as honeydew from vast herds of tiny bugs. The bugs rely entirely on the ants to care for them while they busily suck juices from young leaves or unburst flowers. When the plants start to age, the bugs stop feeding and the herdsmen move in. They tenderly gather up every single bug, both young and adult, completely clearing the plant within an hour or two. The herdsmen now head off, taking their precious livestock with them. Following a chemical trail laid down by scouts, the bugs are carried up toward the lushest-growing tips. The herders now release them to begin feeding in their new pastures. The secret of these ants' long-term success lies hidden high in a bamboo thicket. Their nest, deep in an old bamboo log, is the heart of an operation that only a complex society could run. Thousands of ants link legs to form a living cradle to support a new generation of herdsmen. These roofs and walls of living ants also shelter expectant mother bugs, whose tiny yellow young are born here and then taken out to feed. After a few weeks in one place, the living scaffold begins to untangle. The most pivotal event in their farming calendar is imminent. For these herdsmen are nomads, and regularly move the entire operation, taking all their own young and their breeding stock of bugs with them. They take the jungle obstacle course in their stride, linking together to form living bridges over awkward gaps. The colony settles into a new home selected by scouts for easy access to their new pastures. Partnerships between ants and other creatures have evolved over a hundred million years, so the fact that they work so well is no surprise to Ed Wilson.

EDWARD O. WILSON: But ants go far beyond just animal husbandry. They've also become gardeners and agriculturalists, and in so doing, they run a good part of the plant world in a far more intimate and harmonious way than human beings have ever achieved. The South American plant Cecropia has one of the closest relationships of all with ants. Its hollow stem gives them a home, and it provides a daily crop of little white nodules to feed them. The ants harvest this crop rapidly, and carry it back into the nest. The starchy nodules are produced exclusively for the ants, who eat very little else. Inside the stem, the huge queen lives in safety, surrounded by piles of grubs. No home could be better. But why should the plant be so hospitable? When it's threatened, the reason becomes clear. These tiny ants, which are pouring off the tree onto my hand, as the Cecropia plant's private army. Scientists have very appropriately given them the name Azteca, after the Indian warrior nation. Even though they are only a millionth my size, they're able to drive me off pretty quickly with their sharp little jaws. But their real importance is the protection they give against the plant's natural enemies.

BILL MASON: Many insects like this beetle feast on Cecropia leaves, unless they meet resistance. But a plant with an army of ants to defend it is safe. Buying protection with ant food pays off in a big way. Cecropia, with a lot of guards, thrive, and the ants affect the plant world in even more spectacular ways. Teams of tiny gardeners shape entire landscapes. Up to half the wild flowers in American woodlands are planted by ants. Spring beauties, violets, Trillium, and many others encourage ants, not birds or mammals, to sow their seeds. Some produce pods which fall and burst open, while others lay their seeds directly on the ground for the ants to distribute. But this is no free service. The ants are enticed by the white flesh on the seeds, whose taste they find irresistible. Unselfish as ever, the ants carry these treats back home to share. Their nest is just below ground, where the ants tend their hordes of hungry young. These tasty prizes attract workers chained to underground duties, for their flesh is a delicious kind of fruit—the strawberries, apples, and melons of the ants. Chewed seeds are dumped in compost heaps inside the nest. They look damaged, but are perfectly healthy, and are ideally placed to germinate. Ants are now known to disperse thousands of different plants around the world for such bribes. In Amazonia, ant horticulture goes even further. Ants grow hanging gardens here, rooted in nests of chewed plant fiber. Right on their doorsteps, all sorts of flowers bloom, and this floral display is more than just for show. The blossoms produce nectar on demand. When the ants take the seeds inside the nest to germinate, the garden is maintained, and new growth ensured. The hanging gardens of Amazonia are a natural wonder, created entirely by ants. And the clearest evidence that ants control their world has just been discovered in the steamy jungles of Peru. Thousands of different plants grow side by side here, more than anywhere else on Earth. And yet, amidst this rampant foliage, are mysterious clearings known as gardens of the devil. Hemmed in by dense jungle, areas the size of tennis courts contain just two kinds of plant, with bare leaf litter below. The Peruvian Indians believe black magic is at work, and leave the fruits well alone. But the gardens really belong to ants. Although these ants are particularly small and feeble, they live in enormous extended families in the hollow stems of the two plants that grow in the clearings. Each day, thousands of ants pour down onto the forest floor. They're waging a long-term war against the encroaching jungle. Every alien seedling is attacked with slashing jaws and herbicide. They spread formic acid from poison glands onto the young shoots, and chew away persistently at leaf stalks to cut off the life-giving sap. Although each ant is tiny, so many attack that every seedling is killed. By weeding out invading plants, they remove potential homes for fiercer ants, and keep areas—in ant terms, the size of New York City—to themselves. But the most famous tropical ants are not so much weeders as plunderers of plants. Leafcutter ants remove more greenery than any other animal from South American forests, and they devastate human crops. They use powerful jaws to slice the thickest leaves. Each segment is the equivalent of a five hundred pound weight. But ants have tremendous strength. Their labors continue day and night, in a complex process involving many ants of all sizes doing different jobs with great efficiency. The scale of the operation is vast. Returning to their nests, leafcutters run the ant equivalent of a marathon, at a four-minute-mile pace all the way. In Ed Wilson's eyes, theirs is the most impressive of all ant societies.

EDWARD O. WILSON: This is the surface of the nest of just one colony of leafcutter ants. A colony this size can hold as many as two or even three million workers, all the daughters of a single queen that they keep deep down inside the nest. As the foragers go into the nest, they proceed on downward for as much as fifteen, twenty feet. That's, in human terms, equivalent of about a mile. In its life span, the colony can move as much as forty thousand pounds of soil. That's the ant equivalent of the Great Wall of China. That means that the leafcutters are pretty vital elements of the rainforest ecosystem. They move, they aerate, they fertilize more soil than earthworms. A colony like this has the appetite of a full-grown cow, and the colonies all around consume almost a fifth of the vegetation growth every year. It's an onslaught, yet the forest keeps flourishing. How is that possible?

BILL MASON: Long-term studies show that leafcutters have favorite targets, and go to great lengths to reach the tender, new leaves high in the canopy. They soon move on to strip other trees along trails they've cut in the forest. In time, the same trees are attacked again, but not before they've recovered fully. We humans are much less careful. People often have a harmful impact on the planet, while the social ants run their world in a more stable way. They have had far longer to get things right. And it shows.

EDWARD O. WILSON: Social existence has paid off in a very big way in evolution. Ants and other social insects are, by a long margin, the most social small animals, and they're also the most abundant. And of course, human beings are, by a wide margin, the most social big animals of any kind. The question I guess I'm most often asked is, what are the similarities between ants and human beings, particularly in their social behavior? And my answer has to be, not many at all. But there are some very important differences, and then you look at those closely, then you do illuminate the human condition somewhat. I guess that the real difference lies in reproductive rights and expectations. Essentially, a worker ant or a bee, wasp, termite, doesn't have any. They are bound to the colony in the way that makes them meaningful only as members of the colony. They are little robots, programmed to do work for the colony to survive. The exact opposite is the case with human beings. We join societies and we work to make them succeed—primarily for ourselves. We've learned how to cooperate to an extreme degree. We are capable of altruism. We do it by the unique genius of human behavior, which is the ability to form long-term binding social contracts. But in doing it, in building up a society that is so enormously successful, we have entered into an eternal paradox, a tension between individuality and self-serving, on the one side, and the needs of the society on the other, that makes individual success guaranteed. And that is, I'm afraid, inherent in the human condition. We will always suffer that tension and walk the fine line. The question inevitably comes to mind, that is these inherent weaknesses in human society ever prove fatal, and if we ruined the planet for ourselves and disappeared, how would our own extinction affect the world we left behind? I believe that ants and other social insects would hold on somewhere, and life would pretty much come back to what it was before we arrived on the scene. Then, the ecosystems would return to a balance, and the ants and the other social insects would be right there with them, filling the environment as before, and going on as before, probably for tens of millions of years into the future.

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