A couple of years ago, when the Cincinnati Zoo announced that it was going to try to breed two Sumatran rhinos who were brother and sister—Harapan and Suci—the news made international headlines. To many, it brought home just how dire the species’ situation is: Only about a hundred Sumatran rhinos remain in the world.

Now, in a last-ditch effort to save the species, the Cincinnati Zoo has announced it is sending its male rhino, Harapan—the last Sumatran rhino left in the United States—to a breeding facility on Sumatra. There it is hoped that he will mate with a female named Rosa , who was brought into captivity after she began wandering outside the national park where she was born.

“We are hoping she and Harapan will hit it off,” said Terri Roth, the Cincinnati Zoo’s vice president for conservation and science. She described Harapan, who’s eight years old and weighs 1,800 pounds (more than 800 kilograms), as extremely eligible: “He’s a really fun rhino. He seems like a little bit of a pistol, quite frankly.”

One Rhino’s Story

Harapan’s life story begins with what might be called the second-to-last ditch effort to save the Sumatran rhino. The species, Dicerorhinus sumatrensis, once browsed its way all across southeastern Asia, from the foothills of the Himalayas in India and Bhutan to Borneo and Sumatra. By the early 1980s, its range had contracted to a patch of peninsular Malaysia and a few scattered parks on the islands, and its number had been reduced to a few hundred. At a meeting of experts held in Singapore in 1984, it was decided that some animals should be taken into captivity as an insurance policy against extinction.

Sadly, what followed was almost a textbook study of what can go wrong when trying to save a species. Several animals caught in peninsular Malaysia were killed by disease. Others, on Borneo, succumbed to injuries sustained during capture. Seven animals were sent to zoos in the U.S. A decade later, only three were still alive, each in a different city. At that point, the Bronx Zoo and the Los Angeles Zoo agreed to send their rhinos—both females—to Cincinnati, which had the only surviving male.

Sumatran rhinos turn out to have perversely complicated reproductive lives . If a female does not regularly get pregnant, she tends to develop problems, such as uterine cysts, that render her infertile. Meanwhile, if females don’t sense a male around, they won’t ovulate. The team at the Cincinnati Zoo, led by Roth, eventually figured all this out. Once they finally did, the zoo’s captive rhinos produced three calves— Andalas , Suci, and Harapan. (Harapan means “hope” in Indonesian.)

All of the rhinos originally sent to the U.S. are now dead. So is Suci, who died of hemochromatosis, a disease in which excess iron builds up in internal organs. Andalas was transferred to Indonesia in 2007, and has since fathered one calf at the breeding facility, which is situated in Way Kambas National Park. That leaves Harapan.

Finding A Mate Is Hard

It also leaves the question of how best to deal with the few Sumatran rhinos that remain. They are split among Way Kambas and a few other parks on Sumatra. With populations in each region so low, it’s possible that rhinos aren’t encountering one another, which means that females are likely developing reproductive problems. This cycle may be one of the reasons the species is spiraling toward oblivion.

“There are some people who think all of the rhinos ought to be taken into captivity and managed intensively and bred,” Roth said. “There are others who still want to protect the wild populations.”

A few years ago, the Malaysian government decided it would try to capture all of the Sumatran rhinos left on Borneo; this attempt led to the discovery that, in fact, the animal is now extinct in the wild there. (Two females were captured in that effort, but both have turned out to be infertile.)

Precisely because Sumatran rhinos are so rare—buying and selling the animals is prohibited under the Convention on International Trade in Endangered Species of Wild Flora and Fauna —Harapan can’t simply be sent off now, even though the Cincinnati Zoo and the Los Angeles Zoo, where his mother was from, have decided to let him go. Several permits are required from the Indonesian and the U.S. governments. Only some of these have been officially granted; zoo officials are hopeful the remainder will come through soon.

When they do, Harapan will be loaded onto a cargo plane for Jakarta. He’ll be accompanied by his keeper and one of the zoo’s vets. From Jakarta, they’ll take a ferry to Sumatra, and then a truck to Way Kambas, on the island’s southern tip. At that point, all potentially fertile Sumatran rhinos will be on Sumatra, and the responsibility for saving the species will rest entirely with the Indonesians—if, that is, it is still savable.