The Kingdom of Rarities (19 page)

The rhino stood motionless as the drug worked its magic. I squeezed the radio collar I was holding and glanced at my watch, the seconds ticking away, until the rhino sank to the ground at the edge of the forest. Finally, we dismounted. “So far, so good,” I thought. Before giving the green light to begin work, however, Sunder waved me and the others back, saying, “Let me test first for full sedation.” Grabbing a stick, he poked at the rhino's broad backside. So much for the textbook: the two-meter-tall rhino jumped to his feet.

The elephants trumpeted in alarm. The men on the ground scrambled for safety, trying not to be trampled by the fleeing rhino or panicked elephants. Fortunately, no one was hurt and the moment of bedlam passed. Behind them, Vishnu, the other trackers, and the elephant drivers howled with laughter. The excitable chief park warden, Ram Pritt Yadav, joined in. Hilarity in the aftermath of near disaster was practically a national custom.

Sunder was already preparing another drug cocktail for a second attempt. The trackers gathered round. He explained, “Either the contents of the first syringe didn't inject at all, or, most probably, it only partially injected.” This seemed like a plausible hypothesis, preferable to the alternative—that modern sedatives had no effect on ancient pachyderms.

The rhino was still in the vicinity, and within minutes we had repeated the drill: encircle, dart, wait until the drug put the rhino
under its spell. This time it worked, and soon we were swarming over the sleeping male, covering his eyes and plugging his ears to minimize arousal and attaching the radio collar. “Forty-five centimeters,” I said to Ram Kumar Aryal, who was writing measurements on a data sheet. I had just measured the massive horn, as long as a chair leg. We tested the collar's transmitter, and it sent out a strong signal. The beacon would allow us to locate the male with minimal effort even when he was in hiding and, after a trial period, enable us to habituate him to our presence on elephant-back. We could then learn where he lived, the pattern of his movements, and more intimate details associated with breeding.

Our team posed for a group picture, gathering around Yadav, as we named the rhino in honor of the presiding chief warden. Then it was time to saddle up and, from the safety of elephant-back, watch the rhino wake up. Vishnu stood next to the massive head and held the rhino's ear so Sunder could find a vein. The skilled vet administered the antidote and then both men remounted quickly. The drivers and trackers sat in awe of modern pharmaceuticals: a few drops of a drug a thousand times more concentrated than morphine to knock down a massive rhinoceros, a few more drops of the fast-acting reversal agent to right the beast. In less than thirty seconds, Yadav was rejuvenated. The big male shoved off, uttering deep, huffing grunts in cadence with its departing trot.

As we headed back to camp, one of the drivers burst into song and was joined by a chorus of colleagues. A celebration lay ahead. There would be feasting, folk songs and native dances, and a retelling, for at least the tenth time, of the day's big adventure. For me, the capture was burned into memory: on that foggy morning, there in the elephant grass, I had touched my first unicorn.

I continued to study this remarkable species for several more years in Nepal, and my fascination with rhinos continues to this day, even as they barely hold their own or, in some cases, hurtle toward
extinction. In the 1700s millions of rhinos were alive, but by 2011 the numbers of the five living species together totaled slightly more than 28,000 wild individuals. Most common are the 20,140 southern white rhinos, followed by the 4,840 black rhinos, all in Africa. In Asia, there are 2,900 endangered greater one-horned rhinos. The Sumatran rhino, of which there are about 250 left, and the Javan rhino, with a population of fewer than 50, are among the rarest mammals on Earth.

A species can have a narrow range and low density and yet, as we saw with birds of paradise, bowerbirds, and even Kirtland's warblers, can still be easy to spot if you look in the right places. The same is true for three of the rhinos, the white, black, and greater one-horned. No such “good viewing habitat” exists for the other two species. Would that statement have been true two thousand or even fifty years ago? To a conservationist, the question might seem academic. They are rare now, so it is better to address the immediate, pressing issues of poaching and habitat loss. Yet, to craft a longer-term strategy, biologists need to know under what conditions rhinos might once have flourished, in order to understand how it might be possible for them to flourish again.

A little paleontology greatly aids our understanding. The fossil record shows that rhinos first appeared in the late Eocene epoch (35 million years ago), the earliest known rhinoceros-like mammals having been described from fossil deposits in Asia, North America, and Europe. They looked nothing like the giants of today. Instead, these primitive rhinoceroses resembled early horses and tapirs, rhinos' nearest living relatives. They were diminutive and delicate, were probably abundant, and lacked horns. Between the late Eocene and Oligocene (about 33 to 23 million years ago) perhaps the most dramatic change was an increase in body size from the ancestral forms to larger, more recent body types, a phenomenon frequently observed in mammals. This is an example of Cope's rule—that species within a lineage tend toward gigantism over evolutionary time. Another, more recent development was the
appearance on the rhino skull of a unique, boneless horn. Two traits helped the rhinos to spread widely across the landscape. The evolution of broad feet with three toes allowed them to adapt to marshy habitats and expand their range. Of greater ecological importance were increases in the size and height (from the gumline) of high-crowned molar teeth to better handle a diet of coarse grasses.

Growing so large was probably a defense against natural predators. After rhinos reached a certain size, there were no longer any natural enemies large enough to kill any except the very young calves. Rhinos filled every herbivore niche possible except the arboreal, although the previously mentioned giant giraffe rhinoceros browsed the limbs of trees. The animal's feeding strategy was to eat a great deal but process the bulk quickly in its giant digestive sac. And being giant herbivores meant they were capable of making a living by eating lush, coarse elephant grasses. No matter how one defines evolutionary success—diversity of species, persistence over time, range size, biomass, or feeding niches occupied—rhinos dominated the early epochs when large mammals flourished, in the late Eocene and the Oligocene. On the basis of their numerical dominance, their biomass within an ecosystem, and the number of diverse, wide-ranging, but now extinct species that once flourished, we can safely say that many ancient rhinos, when compared with other mammalian browsers and grazers, were ecological commoners: widespread and abundant.

So what caused the eventual decline of this group? While large body size does not cause rarity, there is an important implication to it that can be drawn from studies of the mass extinction of large mammals during the Pleistocene epoch. The once abundant large plant-eating mammals—the mammoths, mastodons, and their kind—were especially vulnerable to environmental changes and relatively easy to hunt. Early hunting hit large animals especially hard. A major reason is that large animals, especially herbivores, inevitably have very low reproductive rates. Their persistence depends on high adult survival rates. Thus, even a slight increase in
death rate can bring their numbers down rapidly. When humans, whether early hunters or latter-day poachers, take females from the population time after time, crash is not far behind.

In North America, almost the entire rhinoceros fauna was eliminated between 2.5 and 5 million years ago, and in Eurasia only two lineages survived. One of these gave rise to a form quite similar to the Sumatran rhinoceros of today. Perhaps the most famous member of this line was the woolly rhinoceros (
Coelodonta antiquitatis
), which appeared first in China and moved westward into Europe. This charismatic thick-coated, big-horned species inspired the early painters who decorated the walls of the Lascaux caves in France. It persisted until about 1,200 years ago and ranged from Korea to Spain.

A little ecological history clarifies the swift and widespread decline among all five living rhino species in more recent times. Before approximately AD 1400, when the Gangetic Plain first opened to agriculture, greater one-horned rhinos must have been relatively common in this hot, steamy region. Basing our calculations on densities achieved by rhinos today in prime floodplain habitat, I estimated that perhaps half a million or more grazed along rivers or wallowed in oxbows. Around 1900, there may have been 300,000 to 1 million black rhinos in sub-Saharan Africa. Several hundred years ago, the numbers of white rhinos must have been equally staggering. And Javan rhinos were so common in colonial Indonesia that they were considered garden pests and shot by Dutch tea planters. Even Sumatran rhinos then must have filled Southeast Asian forests with their peculiar whalelike vocalizations. All evidence seems to point to the conclusion that rarity is a relatively recent phenomenon for rhinoceroses and that overhunting, then poaching, and habitat loss have been the drivers of their startling decline.

In that September of 1986, before we had our first successful radio-collaring, torrents of rain had engulfed the Chitwan Valley for three
solid days. Along the banks of the Rapti River, villagers gazed in wonder and fear at the surging brown floodwaters that swept uprooted trees along as if they were toothpicks. As I stood watching above the river's roar, the ecological significance of this event became clear. Floods occur here almost every year, but rare, catastrophic floods are the major structuring force in the one-horned rhino's home ecosystem, redrawing the vegetation map. Had I not been here to witness this rare event, I might have missed seeing how a once-in-a-century or half-century deluge inundates vast areas, reshaping the ecology of the land. Such a flood reconfigures floodplains and oxbows and even shifts the vegetation types over huge areas through the deposition of rich silt carried from the mountains.

Every year, monsoon flooding forces the wildlife of the Terai zone to head to higher ground or risk being swept away. When the threat passes, however, new life emerges. As each year's flood-waters recede, the silt deposited in the grasslands acts as a layer of fertilizer. From that silt, the next year's crop of wild sugarcane will emerge, and rhinos will feed on the shoots. The ability of greater one-horned rhinos to feed on early postmonsoon vegetation maintained by annual disturbance, to track those disturbances, and to disperse among them is vital to their survival.

Fortunately, river-hugging rhinos are powerful swimmers. They can easily ford the flooding waters and are savvy enough to avoid exposed quicksand when waters retreat. Not all of Chitwan's grassland-dependent mammals handle the floods with such aplomb, however. Endangered hog deer are sometimes washed away by the rising waters. The elusive pygmy hog and hispid hare, also called the bristly rabbit, are some of the rarest mammals on Earth and face emboldened predators when floods bury their tall grass cover. Yet such native species must have made some adaptation to the normal range of annual flooding and the once-in-a-century deluges, as species truly unable to cope would have vanished ages ago.