colloquially known as rhinoceros wombats; Thylacoleo carnifex, a tigersize carnivore referred to as a marsupial lion; and the giant short-faced kangaroo. Even smaller islands had their own large beasts. Cyprus had a dwarf elephant and a dwarf hippopotamus. Madagascar was home to three species of pygmy hippos, a family of enormous flightless birds known as elephant birds, and several species of giant lemurs. What happened to all these oversize creatures? Scientists have been debating this question for a century and a half, and they divide into two hostile camps: the climatists and the overkillers. According to the first group, the culprit was the temperature shift that occurred at the end of the last glaciation, 18,000 years ago. According to the second, it was humans who wiped out the megafauna through hunting. One of the earliest climatists was the British geologist Charles Lyell, a mentor to Charles Darwin. Lyell attributed the megafauna’s demise to “the great modification in climate” caused by the ice age. Darwin agreed with Lyell, though only reluctantly. “I cannot feel quite easy about the glacial period and the extinction of large mammals,” he wrote in a letter to Alfred Russel Wallace, another of the nineteenth century’s great naturalists. Wallace, for his part, initially favored a climatic explanation, but later changed his mind. “Looking at the whole subject again,” he observed in his last book, The World of Life, “I am convinced that…the rapidity of the extinction of so many large Mammalia is actually due to man’s agency.” The whole thing, he said, was really “very obvious.” The debate drags on, but the most recent research has come down decidedly on the side of overkill. A study of Australian megafauna published in 2012, for instance, found that the continent’s giant herbivores died out before any significant climate change had occurred (but, importantly, after humans arrived). The megafauna extinction in Australia “couldn’t have been driven by climate,” Chris Johnson, an ecologist at the University of Tasmania and one of the lead authors of the study, told me on the phone from his office in Hobart. “I think we can say that categorically.” The plight of the Sumatran rhino also supports the case for overkill, if only indirectly. As a general rule, the trade-off for being large enough to avoid predation is a low birth rate: megaherbivores take a mega-long time to give rise to a new generation. Rhinos require six or seven years to reach sexual maturity. Gestation then takes about 16 months. For elephants, the process is even more drawn out; they don’t start reproducing until their teens, and their gestation period is nearly two years. The problem with people (as far as elephants and rhinos are concerned) is that they don’t obey the usual rules of predator-prey relations. Humans can—and routinely do—kill animals that are much larger and stronger than themselves. This alters the terms of the trade-off and turns what was a highly successful survival strategy into a loser’s game. People don’t have to wantonly slaughter rhinos, just as they didn’t have to wantonly slaughter mammoths or diprotodons, to drive them to extinction. All they have to do is depress the already low reproductive rate, and the population will decline. If the pressure is sustained, ultimately it will drop all the way to zero. In the case of the Sumatran rhino, the population has fallen to the point that there are those who argue that all the animals left in the rainforest ought to be pulled out of it. “In my strong opinion, the only way to save this species is to bring them into captivity and make them breed,” John Payne, executive director of the Borneo Rhino Alliance and one of the organizers of the Sumatran Rhino Crisis Summit, told me by phone from the city of
Kota Kinabalu. “This is the heart of the matter. That’s controversial. There’s people saying that’s not the way to do it.” In fact, the Malaysian government has resolved to bring all of the rhinos left on Borneo into captivity, but at this point there are probably fewer than 10 rhinos remaining there. Sumatra, where the rest of the animals live, is part of Indonesia, and the Indonesian government, by contrast, has endorsed a plan to try to preserve its rhinos in parks. The fact that the rhino’s small population is divided between two antagonistic countries may be another reason to fear for its survival, as the two nations often seem to be working at cross-purposes.
ne day in Cincinnati, I arrived at what is
called the rhino’s barn—really a one-story building made of cinder blocks—in time to watch Harapan’s sister, Suci, get breakfast. On an average day, Paul Reinhart told me, Suci goes through about 100 pounds of ficus. (Providing her and Harapan with browse costs the zoo about $200,000 a year.) Once the ficus leaves were gone, Suci started in on the branches. These were an inch or two thick, but she crunched through them easily, and continued on until only a few stray twigs remained. Reinhart described Suci to me as a “good mix” of her mother, Emi, and her father, Ipuh, who died just a few months before Harapan returned. (E. O. Wilson, who once spent an evening with Emi at the zoo, described the encounter as “one of the most memorable events” of his life.) “Emi, if there was trouble to get into, she’d get into it,” Reinhart recalled. “Suci, she’s very playful. But she’s also more hardheaded, like her dad.” Suci is so used to being around people that Reinhart let me hang out with her while he went off to do other chores. I stroked her hairy flanks. Sumatran rhinos have pebbled skin that makes petting them feel a bit like rubbing a tree trunk. Though I can’t say I sensed much playfulness, Suci did seem to me to be affectionate, a little like an overgrown dog. (In fact, rhinos are most closely related to horses.) At the same time, I recalled the warning of one zoo official, who had told me that if Suci suddenly decided to jerk her enormous head, she could easily break my arm. After a while, it was time for the rhino to go get weighed. Some pieces of banana were laid out in front of a pallet scale built into the floor of the next stall over. When Suci trudged over to eat the bananas, the readout from the scale was 1,507 pounds. The Cincinnati breeding program demonstrates how seriously humans take extinction. Such is the pain caused by the loss of a single species that people are willing to perform ultrasounds with their arms deep in a rhino’s rectum, if there’s even a chance that this will help. Time and again, people have shown that they care about what Rachel Carson called the “problem of sharing our earth with other creatures,” and that they’re willing to make sacrifices on those creatures’ behalf. But just as clearly, the breeding program shows the limits of such desperate efforts. Once a slow-to-reproduce species like the Sumatran rhino is down to its last 100 individuals, there just aren’t many options left. Terri Roth told me that she was already starting to look for a new project to turn her attention to, because “if there are no other long-term solutions, I don’t want to continue to inbreed.” It is painful to imagine a world in which the Sumatran rhino has no place. But it’s getting increasingly difficult to see what that place is. spring 2014
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