Milky rivers, such as the Amazon and the Madeira, generally have their origins in the west and are clouded by the heavy sediment load that they carry down from the youthful Andes. Blackwater rivers, on the other hand, usually come from the ancient Guiana Highlands in the north and so wash over nutrient-poor, sandy soils. Scoured by millions of years of hard rains, these soils cannot retain decomposing organic matter—mostly leaves—which, when swept into a river, literally stains the water black like tea.
Although during the rainy season the River of Doubt is nearly as black as the Negro and as murky as the Amazon, it is technically a clearwater river. Like the Amazon’s largest clearwater rivers, the Tapajos and the Xingu, it has its source in the Brazilian Highlands, and so it picks up very little sediment as it flows over ancient and highly eroded soil. Clearwater rivers are also less acidic than blackwater rivers. Some, most notably the Tapajos, are so clear that they look blue, perfectly mirroring the sky above them. But most, like the River of Doubt, mix with either blackwater or milky tributaries as they snake through the rain forest, and so look neither blue nor clear by the time they reach their mouth.
For Roosevelt and his men, the color of the River of Doubt was of interest primarily for what it revealed about the speed and character of its course. The same eroded crystalline plateau that kept the river largely sediment-free was also banded with alternating layers of soft young rock and hard ancient rock, each of which had been exposed by the carving force of the river, creating a perfect breeding ground for waterfalls and rapids.
At around three-thirty that afternoon, the men heard a low roar that traveled upstream like distant thunder before a rainstorm. Over the ensuing weeks, this roar would become for them one of the most alarming sounds in the Amazon: the sound of rapids. With a heightened sense of expectation, they allowed themselves to be swept along on the swift current until they reached the first rapid. Although lively, it was small, and the expedition’s three canoes and two balsas easily bumped through its turbid water. The men’s relief at having successfully navigated this first obstacle, however, was short-lived. “Instead of finding quiet waters at the foot,” Cherrie wrote, “the current ran faster and faster until we were whirled along as though through a mill race.”
Suddenly the river made a sharp turn, and when they rounded the bend, the men saw a seething cauldron of white water, the prelude to world-class rapids. Surprised by the stark transformation of their placid river, they quickly drove their canoes ashore so that they could decide what to do next from the relative safety of the bank. It was impossible from this vantage point to tell exactly what was whipping the river into such a frenzy, but they did not want to find out while they were still in their clumsy dugouts. Leaving the camaradas behind to set about clearing a spot for their camp, the officers cut a path along the bank so that they could see for themselves what awaited them downstream.
They were disheartened by what they found. Stretching before them for nearly a mile was a series of rapids that included two roughly six-foot waterfalls. The river sped, Rondon wrote, “with enormous velocity” through rocks of friable sandstone that had been “deeply cut out, smashed to pieces and thrown one on the top of the other by the rushing force of the waters.” Once over the falls, the river briefly divided into two branches as it swept past a small island—“the last stronghold of resistance which that ruined ground offered,” Rondon noted—but then came together again to perform a feat that none of them had ever expected to see. The water channel that had been at least a hundred yards wide and proportionally deep just a mile above the rapids now churned through a passage that, at one point, was less than two yards across, transforming the quiet river into a water cannon.
“It seemed extraordinary, almost impossible, that so broad a river could in so short a space of time contract its dimensions to the width of the strangled channel through which it now poured its entire volume,” Roosevelt marveled. In fact, so narrow was this gorge that Kermit took a picture of Cherrie kneeling at its chipped and worn edge and spanning it with his rifle. “No canoe could ever live through such whirlpools,” the naturalist would later write. “Only one glance at the angry waters was necessary for us to realize that a long portage would have to be made.”
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THE PORTAGE around the River of Doubt’s first serious set of rapids lasted for two and a half days. Rondon put everyone to work except Franca, the cook, and an ill camarada, who had already begun to sweat and shiver with fever. Even Kermit, who was suffering from a renewed attack of the boils that had tortured him during the overland journey, helped move their camp to the foot of the falls and, with Lyra, hauled the expedition’s heaviest, waterlogged dugout up from the river. It was only by applying block and tackle that the camaradas were able to get all of the dugouts out of the water, up the bank, and onto level ground. There must have been few men in the portage team who did not recall with deep regret the expedition’s abandonment of Fiala’s 160-pound canvas-covered canoes.
The camaradas had already prepared a corduroy road of heavy logs upon which they would drag the canoes. With axes and machetes, they had hewn a rough path through the jungle’s tangle of trees and snaking vines. Then they began chopping down trees, a job made infinitely more difficult by the broad, load-bearing buttresses that supported most large boles. These trees were cut into hundreds of thick, six-foot-long poles, which were placed on the ground at two-yard intervals to serve as rollers for the unwieldy canoes.
Once the road had been laid, the real work could begin. Harnessing themselves to a drag rope, the camaradas lined up two by two like draft horses to pull the dugouts over the crude skidway. The only help came from one man who stood behind them with a lever and tried to pry the canoes over the gnarled, uneven logs. It was in this way—“bumping and sliding,” Roosevelt wrote—that the seven dugouts painfully “twitched through the woods.” For the camaradas, the pain was not limited to their massive, awkward loads, or even to the rough rope that blistered their sweat-slick hands and sawed heavily into their shoulders. As they cut through the jungle, twisted vines and sharp, grasping branches tore at their clothes and slashed their skin. The hot, humid air felt thick in their throats, and they fought off a dizzying sensation of claustrophobia as they fumbled through the close, dense, and seemingly endless fortress of trees along the river-bank.
As the men had feared, the price of encountering impassable rapids was prolonged, intimate exposure to a jungle that seemed increasingly dangerous and enigmatic. Common sense and scientific respect for the jungle told them that there must be an abundance of animal life in this part of the Amazon, as in every part, but there was very little to be seen. The men frequently saw trails left by tapirs and peccaries, piglike mammals, but they were always empty. So far, they had had little opportunity to hunt, and no luck even fishing. The only creatures in evidence were the insects, which seemed to grow increasingly bold and aggressive the deeper the men traveled into the rain forest.
In fact, as the men of the expedition labored to build their portage road, the jungle around them was teeming with life. While on land, the members of the expedition could not sit, step, lean, or stand without entangling themselves in the predatory ambitions of some creature or, more often, hundreds of creatures of the Amazon. Yet the same evolutionary competition that filled each branch, shadow, and muddy puddle with an unparalleled diversity of living things also ensured that those forms of life were virtually invisible to Roosevelt and his men. Those glimpses of activity that they did manage to see, moreover, were often calculated for the specific purpose of confusing and misleading them.
Rarely in the rain forest do animals or insects allow themselves to be seen, and any that do generally do so with ulterior motives. In a world of endless, life-or-death competition, the need to hide from potential predators and deceive sophisticated prey is a fundamental requirement of longevity, and it has produced a staggering range of specialized attributes and behavior aimed at manipulating—or erasing entirel
y—any visible form that an enemy or victim might see. So refined is the specialization of life in the rain forest that every inch of the jungle, and each part of the cycle of day and night, has plant, animal, and insect specialists that have adapted to exploit the unique appearance-altering potential it offers.
The most common defensive tactic, used by many or most of the animals that Roosevelt and his men had expected to see, is simply to hide, biding time in hollow trees, carefully constructed burrows, or camouflaged nests high in the canopy, and emerging only under cover of darkness. The tent-making bat painstakingly makes small bites along the centerline of large leaves so that they will droop on each side, creating small tentlike shelters that protect them from rain, wind, and sun and render them all but invisible. The lumbering armadillo, on the other hand, laboriously digs a burrow that it inhabits for as little as a single day, only to abandon it in the interest of finding even greater safety and invisibility elsewhere.
To make the job of hiding easier, some creatures develop camouflage, or cryptic coloration, to help them disappear even in the plain view of potential predators. A ten-foot-long gold-and-brown-striped boa constrictor can all but vanish on the dappled forest floor. Caterpillars of the geometrid moth are almost indistinguishable from twigs, and katydids look like nothing more than green leaves. Fishes of the Aspredinidae and Anabantidae families also specialize in looking like twigs and leaves, blending in with the detritus carried along by the river’s current.
When protective coloration does not come to them naturally, some creatures have developed relationships with plants or insects that can do the job for them. The three-toed sloth, for example, a long-limbed, short-bodied mammal that lives in high trees, can nearly vanish while hanging upside down from its clawed feet. As a mammal that is typically grayish-brown in color, the sloth has no natural way of blending into the green coloration of the forest canopy. Each of its hairs has therefore evolved to contain microscopic grooves that become filled with algae, giving the sloth a greenish sheen that allows it to disappear when viewed from the ground.
Given their high numbers and stealthy habits, it is virtually certain that sloths were a constant presence as the men of the expedition fought their way through the forest below. Yet they remained undetected. In a world in which most animals have to fly, run, swing, or scurry in order to elude predators, the sloth has made a virtue out of immobility. The mere fact that it moves slowly and rarely—its head can rotate more than ninety degrees, so that every other part of its body can remain motionless—makes it almost impossible to see. So perfectly has the sloth adapted to its strange treetop life-style that its hair grows forward to allow the rain to drip effectively from its inverted body, and its sharp, curved claws are so specialized for the job of clinging to branches that the female cannot even pick up her young to carry them on her back—they must climb on by themselves after they are born.
To the degree that some creatures cannot avoid being seen, many adopt disguises to confuse, startle, or mislead potential enemies. The wings of many butterflies bear round, eye-shaped patterns which flash into view at the moment of flight, frightening potential predators by suggesting the face of an owl or a bird and buying a precious second of confusion for the butterfly to escape. The caterpillar of certain sphinx moths can contract its muscles so that it looks convincingly like the head of a small viper. To complete the illusion, it even sways slowly back and forth, much like a viper ready to strike.
The value of disguise and deception is not limited to defense against predators, and can also become a centerpiece of offensive strategies, like the remarkable Trojan Horse ploy used by the South American crab spider to capture the carpenter ants on which it feeds. After killing an ant, the crab spider, which is only a fifth of an inch long, carefully consumes the contents of the ant’s body without harming the outer skeleton. It then carries the empty carcass over its own body so that, visually and chemically, the spider “looks” like its prey—allowing it to approach new victims undetected. Some plants also assume disguises to fool their evolutionary foes and accomplish their reproductive mission. Certain orchids, for example, attract male tachnid flies by mimicking females; when the male tries to copulate with what it believes to be a female fly, it ends up pollinating the orchid.
For some species that deter attack by being poisonous, the goal of their physical appearance is not to hide or confuse other forest creatures, but to be noticed. In order to stay alive, they advertise their toxicity to potential predators through bright, vivid markings known as warning coloration. Some of the most famous practitioners of warning coloration in the Amazon are poison-dart frogs of the species Phyllobates terribilis, which can carry enough toxin to kill a hundred people and need only be touched to be deadly. These frogs, whose toxin is used on the blowgun darts of some Amazon Indian tribes, are as small as a half-inch long. But their bold patterns and vivid coloring are as effective as a neon sign in warning their natural predators of their lethal potential. For outsiders such as the men of the expedition, however, such signals meant little or nothing, and merely ensured that the only creatures they could see as they pushed through the forest were likely to be especially dangerous or even lethal.
* * *
ROOSEVELT AND Kermit had come to the Amazon with the expectation that they would hunt wild game, much as they had done in the wilderness of the Western United States and in Africa. But the relentless advance of evolutionary competition—together with the arrival of human beings on the South American continent thousands of years before—had largely eliminated the big, conspicuous game animals that Roosevelt had become famous for hunting elsewhere.
For much of its history, South America was home to a striking array of large animals like those Roosevelt would have associated with Africa or Asia. Although the reasons for the abrupt and dramatic loss of life are not certain, many scientists believe that the impact of human migration was decisive. In contrast to Africa and parts of Asia, where animals evolved alongside early humans and learned to fear them, South America was the last continent to be populated by humans, who by that time had become sophisticated hunters. With no understanding of their new predator, the large animals of South America were prime prey for the arriving humans, and most of them were soon driven to extinction.
Of the mammals that remain, the jaguar is the undisputed king. Cherrie would never forget an earlier expedition along the Paraguay River, when his party had been terrorized by a single jaguar. “Few people have heard a horse scream,” Cherrie wrote, still bothered by the memory of the sound. “When the jaguar started in the direction of our horses they literally screamed with fear and lunged about fiercely. Several broke their hitchings and went tearing away into the forest!”
For all its ferocity, however, the jaguar was too wary and elusive to constitute a real danger, and while other jungle mammals, such as peccaries, could be dangerous, they, too, were so scarce that the men would have welcomed the chance to encounter one in return for the possibility of a good meal. As they were quickly learning, the greatest challenge they faced from the rain forest came not from any creature or adversary that they could confront and defeat, but from the jungle as a whole—in the ruthless efficiency with which it apportioned food and nutrients, in the bewildering complexity of its defense mechanisms, in the constant demands that it placed upon every one of its inhabitants, and in the ruthlessness with which it dealt with the weak, the hungry, or the infirm.
To witness the devastating impact of this kind of danger, the men needed to look no further than the insects that filled the air around their faces, and swarmed over every tree, vine, and leaf they touched. Rondon, who had for decades watched his men be tortured, infected, and driven to the brink of madness by the jungle’s multitude of insect pests, knew better than most what power such small creatures could wield. The Brazilian colonel, Roosevelt wrote, regarded the threat that even jaguars posed as “utterly trivial compared to the real dangers of the wilderness—the torment and menace of at
tacks by the swarming insects, by mosquitoes and the even more intolerable tiny gnats, by the ticks, and by the vicious poisonous ants which occasionally cause villages and even whole districts to be deserted by human beings. These insects, and the fevers they cause, and dysentery and starvation and wearing hardship and accidents in rapids are what the pioneer explorers have to fear.”
So important and ubiquitous are insects in the ecology of the Amazon that, notwithstanding their generally small size, ants alone make up more than 10 percent of the biomass of all the animals in the rain forest. From tiny parasitic red mites to cyanide-squirting millipedes to giant six-inch beetles with legs so powerful that they require two men to pry them off if they grip a human arm, the insects of the rain forest have achieved an unparalleled degree of specialization, seeking out every possible source of sustenance and advantage. They accomplish this through adaptations that extend far beyond mere physical attributes and individual behavior, and reach into the realm of complex social relationships that involve not only other members of their own species but sophisticated alliances with other forms of life as well.