The Kingdom of Rarities (9 page)

Monkeys may be hard to spot, but they glow like neon compared with jaguars. Few veteran tropical biologists have ever met a wild jaguar; according to those who have, a prolonged encounter is usually a once-in-a-lifetime event. The cat's exquisite pelage of black
rosettes on an amber background stands out in animals on display in zoos and on wall calendars, but that coat camouflages them in the dappled light of the forest understory.

Many biologists who attempt to study rain forest mammals eventually give up and shift to some other project. It is not for lack of trying. Rain forest mammals shrink from plain view. Many are nocturnal and diminutive; they scurry under leaves or, like the most abundant group—bats—roost in caves or shelter under dense boughs until nightfall. But even large vertebrates that are active by day are expert at staying out of sight, especially where hunters stalk them.

George's two target cats—jaguars and pumas—are among the most wide-ranging mammals in the region. The jaguar roams from Arizona to Argentina, but unlike many tropical rain forest denizens it can live in desert conditions. Like most large predators, however, it always occurs in low densities. The puma, also known as the mountain lion or cougar, can be found from the Yukon south almost to the tip of South America in the mountains of Tierra del Fuego. Like the jaguar, the puma has many ecological addresses, from the edge of arctic tundra to tropical wet mangroves, but never exists in large numbers. Unlike jaguars, pumas are one of the most studied of all large cats, except in the Amazon. Here, their ecology remained a mystery until George became intrigued by them.

How do the two big cats fit together in this ecological puzzle? “I began to wonder,” George told me, “do the smaller pumas share space with jaguars under the rain forest canopy? Do they hunt the same areas for prey?” Reduction of prey by another top predator would only boost the total area needed to support a pair of breeding jaguars, say, and make the answer to “How much is enough?” frighteningly large. Of course, from the perspective of a territorial male jaguar, even one nearby male jaguar or puma might be too close for comfort.

Since these questions all related to what rarity is, I began to wonder about the relativity of our definition and how we understand the
concept. Do jaguars and pumas even qualify as rare species? Some biologists point out that when it comes to rarity, both of these big cats, as well as the lion and the tiger, have such a widespread distribution that it may compensate for their low density wherever the species occurs. Rarity, they argue, really depends on the scale you are talking about. Other scientists argue that explaining the rarity of jaguars and pumas is as simple as looking at a food pyramid, as Paul Colinvaux summarized in his aptly titled 1979 book
Why Big Fierce Animals Are Rare
. It takes a lot of prey animals to support a healthy population of large carnivores. Biologists refer to different levels of food gathering by organisms as “trophic levels,” which can be visualized as a pyramid with the largest meat eaters at the apex, followed by fruit and insect eaters, then plant eaters, and finally the plants and fungi themselves at the base, supporting the whole structure. Species that occupy the top of the food chain are always scarce, whether on land, in lakes or streams, or in the oceans. Thus, in the rain forests of the Amazon, the Congo basin, or Asia, the largest flesh eaters, as dictated by the laws of thermodynamics and energetics, have to be much fewer in number than the large herbivores they eat. But how do the causes and consequences of rarity vary as one moves down the tropical food chain, from big, fierce cats, large herbivores such as deer and tapirs, monkeys, and macaws to the trees themselves, which give the forest its three-dimensional structure? The work of George, Sue, and other colleagues has brought these issues to light.

Knowing something of the density of the cats' prey could help George to better understand patterns of rarity among those that stalk them. Meet the forty-kilogram white-lipped peccary, a shaggy, piglike forest specialist and a primary prey item of both jaguars and pumas. Unlike the jaguar, a peccary moves in the company of hundreds of its family members and associates. Peccaries are constantly on the go and travel long distances over the year; it is still not clear whether they are nomadic or migratory. Unlike cats, peccaries make their presence obvious. Rooting peccary groups leave
conspicuous pockmarks and furrows in the soil and announce their presence with grunts, screams, and tooth clacking. The sound track is accompanied by an overpowering barnyard cologne, an especially pungent odor that peccaries emit when excited.

George and Sue chose the remote Madre de Dios area of the Amazon, and the Los Amigos Biological Station in particular, for their studies. Los Amigos offered a rare chance to study wildlife in a hunter-free zone. Somewhat like the Foja Mountains of New Guinea, Los Amigos can be used as a control site for other studies conducted in places where hunting is intense. At Los Amigos, George had the opportunity to study predator and prey populations, and Sue could study monkey troops, where their subjects' numbers and behavior were less influenced by human contact. For example, high densities of peccaries where they are neither shot nor snared might offer different insights into the wanderings and densities of cats from findings in locations where prey has been decimated by hunting, as it has been in a forest area of Madre de Dios near Puerto Maldonado, southeastern Peru's regional population center. These contrasting sites permitted George to study how wildlife responds to intrusion and even invasion. Near town, machetes and chain saws were carving up this once isolated stretch of the Amazon. Tens of thousands of gold miners were digging in the forest and dredging the riverbanks. Construction was under way on the new Transoceanic Highway, linking Brazil with the Pacific Ocean. Completed in 2010, it now connects southeastern Peru to the outside world—and it fragments what was one of the largest expanses of undisturbed rain forest. Thousands of poor villagers from the high Andes had already settled along the way in search of work, and more were arriving daily to seek their fortunes in the Amazon lowlands, as had the forty-niners in California 150 years before. The human migration is ongoing, despite the history of nearby Rondônia, Brazil, where in the past few decades thousands of settlers have staked their dreams on a piece of Amazon geography only to find livelihood unsustainable on its poor soils.

Map of the southeastern Peruvian Amazon

The shrinking of the rain forests because of human settlements introduced a new set of research questions for the husband-and-wife team. How had loss and fragmentation of rain forest and new levels of human influence, especially hunting, affected answers to the initial questions of how much is enough, for jaguars, for pumas, and for sakis? Given the pace of forest degradation, finding answers to these questions is urgent.

For the past four years, George had contracted with a locally run air taxi company to help him track the animals he and his field team captured and fitted with radiotelemetry devices. It was time for the near-monthly flight to pinpoint the animals' locations, and George
had offered to take me along. At the grassy field that served as an airstrip, George greeted his pilot, Jonathan Schmidt, and quickly attached his tracking gear to the plane.

George was always keen to apply a new technology or to tinker with older versions. When his research began four years earlier, in order to learn how many jaguars lived in this area and how much of which habitats they used, George and his colleagues placed automatic cameras known as camera traps in the dense forest to document the presence of species, such as jaguars, that shun detection by human eyes. A camera is set up along an animal trail, and whenever a moving subject passes in front of it, a sensor is triggered and—
Click!
—a photographic record is made, with an electronic date and time stamp. The results can be breathtaking. With the use of hidden cameras, species that were once ghosts—never seen by anyone or absent for decades—suddenly reappear.

Remote camera traps also enable estimation of actual densities of species that are almost never seen. Biologists have adapted statistical methods to derive numbers from photographic records of known individuals. Luckily, jaguars are perfect for this system because their spot patterns offer unique identification for each cat. The trick, though, is to set up opposing cameras to photograph each side of the passing jaguar (or other spotted or striped cat) because the spot pattern differs on the left and right flanks. If George and his team saturated the forest with enough camera traps placed at proper intervals and covered a sufficiently large area in a relatively short time, they could obtain a density estimate.

Even with the cameras, however, George's question could not be fully answered. The method depends on the area studded with cameras being larger than the home range of the study animal. Yet George's initial camera trapping grid, an area about as large as 10,000 soccer fields, proved too small to contain the entire home range of a single jaguar. In fact, one male used an area eight times larger! At best, the camera trapping effort offered an indication of jaguar presence.

To learn more about their daily movements, George had no alternative but to start catching jaguars and fitting them with tracking devices so that he could map the movements of each individual. The jaguars proved elusive. Adapting techniques from other studies, George and his team set large live traps—baited with pigs, dogs, and chickens, each housed safely in a separate compartment of the trap—in different parts of the forest.

Despite many attempts, these baited traps captured very few jaguars. George called in some expert cat catchers, who suggested that recordings be played of the cats' breeding calls and of vocalizations made by their prey. This decoy did the trick. Within a year, George and his team had more pumas and jaguars radio-collared than had ever been accomplished before in the Amazon.

In a region with no roads, however, tracking radio-collared jaguars on foot or by boat turned out to be futile; even when collared animals were nearby, the dense forest swallowed up the signals—the jaguars might as well have been a hundred kilometers away. In an airplane flying above the canopy, though, the signal was loud and clear, and George could locate all of his collared animals each time with a few hours of flying.

“Let's go find some jaguars!” George shouted to me over the engine noise. He gave a thumbs-up to the pilot, who then set the Cessna hurtling down the grassy, water-soaked runway in hopes of clearing the tall forest wall that surrounded us on all sides. It was a joy and a relief to rise above the living curtain of trees into a beautiful sunrise. Below were trees in a thousand shades of green as far as the eye could see, dotted by occasional ones with young, bright red leaves and a few with crowns awash in yellow or pink flowers.

What appeared to be a single type of forest, however, was many forests in one. Meandering rivers are a trademark feature of the Amazon basin and shape the extent of floodplain forest, where tree species must cope with periodic inundation. The high disturbance levels contribute to floodplain forests being less rich in species than the more stable upland forests, beyond the reach of seasonal
floods. These upland stands are among the most diverse forests in the world. A thousand shades of green may not be far off as an estimate: perhaps as many as 1,000 woody tree and vine species populate the area, though the tree species occur at extremely low densities.

In a clearing along the banks of the Madre de Dios, the buildings of the Los Amigos Biological Station gleamed in the morning sun. As the plane circled, George found his first radio-collared jaguar. Locating jaguars by plane may seem romantic, but it was really a throwback to the old ways of wildlife tracking. The schedule of determining one location a month for each collared cat would yield few answers to George's overarching questions. Frustrated but determined, he considered satellite telemetry using global positioning system collars. But even with expensive GPS collars, he concluded, reception would be possible only when the collared animals ventured into an opening, such as a rare natural clearing or a river sandbar.

The jaguars we were locating now reflected George's most recent solution to the problem of tracking in such dense vegetation. As the plane swung toward the Tambopata River, the signals of two more jaguars pinged in the headphones. Since 2006, some of the jaguars below us had been carrying two complementary signaling devices, one traditional—which was giving George the location he heard in his headphones—and the other a piece of wizardry. Mounted on the standard VHF radio collar was a TrackTag, a device invented by the Scottish engineer Peter Brown that obtains a fix in about twenty milliseconds—a significant improvement over normal GPS collars, which take at least ten times that long. Using this technology, George collected thousands of fixes, rather than the few he could obtain using VHF collars, over the course of our three-hour flight on that first of our two-day jaguar reconnaissance.