The River of Doubt (25 page)

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.

*  *  *

R
OOSEVELT 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 attacks 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.

Like that of other rain forest organisms, the physical form of insects has evolved to accomplish a spectacular range of survival-related feats, from living upside down on canopy leaves to flying almost invisibly on transparent wings to biting with pincerlike mandibles so large that they are sometimes used by Indians to suture wounds. The Brazilian wasp
Mischocyttarus drewensi
secretes a chemical repellent from its abdomen that, when slathered onto the stem that holds its nest, forces marauding ants to turn back and abandon their plans of attack. Ants of the neotropical genus
Basiceros
have made themselves all but invisible on the forest floor both by camouflaging their bodies in fine particles of soil that collect in two layers of hair and by learning the value of slothlike immobility. When foraging, the ants move extremely slowly, and if disturbed, they stand perfectly still for minutes at a time, disappearing into the rotting litter around them.

More than any other rain forest creatures, insects have extended and refined their individual capabilities through elaborate social structures. As Roosevelt and his men discovered from their first moments on the River of Doubt, the powerful influence of ants, termites, wasps, and other highly regimented insects comes not only from the particular traits of any single individual, but from the collective, coordinated activities of colonies and hives that can number as many as a million members. Acting in concert, but with highly specialized roles, columns of hundreds of thousands of army ants can fan out in raiding parties fifty feet across at their front lines, harvesting huge numbers of tarantulas, roaches, beetles, scorpions, snakes, lizards, birds, and nearly anything else in their path before returning at dusk with the bodies of their prey to their common bivouac.

Insects have also developed highly refined, mutually beneficial relationships
with other rain forest organisms. Many tropical trees and plants have special sheltering cavities or nectar-producing structures for the benefit of ants, which in return then patrol them vigilantly, defending them against herbivores, tending their leaves, and eating the eggs and larvae of other potentially damaging insects. As a result of such relationships, virtually every growing thing teems with insects; a single tree in the Amazon can serve as home to more than forty different species of ant, rendering even the most casual contact with it a nightmare of painful bites.

At this early point in the Roosevelt-Rondon Expedition, the insects had already become the bane of the men’s existence. On the morning of March 4, Cherrie woke up to find that the poncho that he had spread underneath his hammock the night before was “literally alive with termites.” Unfortunately for the expedition, termites swarm during the rainy season. The mass swarming may be an effort to increase their chances for reproducing, or it may better their odds for surviving their countless predators. Whatever the reason for this invasion, every man suffered because of it. The termites ate Cherrie’s duffle bag, the red lining of Roosevelt’s helmet, and even one leg of the former president’s underwear. “When the Colonel held them up for our inspection there was a shout of laughter,” Cherrie recalled. “But I don’t believe he relished our mirth.”

Roosevelt might have found more humor in the situation if he had had underwear to spare. As it was, he had precious few pairs left. Not only had he left some of these essential items behind in an effort to reduce his personal belongings during the overland journey, but he had also lost some to another, earlier attack. One night near Utiarity, while he and Kermit were sleeping, one of the expedition’s pack oxen had gotten into their tent and feasted on their underwear.

The insects were more than destructive. Their bites were maddening and painful, forcing even strong men to seek shelter. “Our hands and faces were swollen from the bites and stings of the insect pests,” Roosevelt complained. Each night when he sat down at his little
portable table to work on his
Scribner’s
articles, Roosevelt had to pull long, fringed gauntlets over his hands and arms and drape his sun helmet in mosquito netting that hung heavily over his face.

To fight off the insects, the men had at least one useful weapon besides clothing and netting: fly dope. Developed in the late nineteenth century, fly dope was one of the first chemical insect repellents to be introduced in the United States. “I had never before been forced to use such an ointment, and had been reluctant to take it with me,” Roosevelt admitted. “But now I was glad enough to have it, and we all of us found it exceedingly useful. I would never again go into mosquito or sand-fly country without it.”

As welcome a relief as it had been, however, the small quantity of fly dope that Roosevelt had brought with him was hardly sufficient compared to the sheer scale of the insect life that the expedition encountered as it made its way down the River of Doubt.