Sumatran rhinos were once widespread across southern Asia; today, fewer than 100 are believed to be left in the wild.
An international captive breeding program was launched in 1984, sending rhinos to the United States and United Kingdom.
The first calf wasn’t born until 2001, because maintaining and breeding these rare rhinos turned out to be an unusual challenge.
This is Part One of a two-part series about attempts to rescue Sumatran rhinos from the brink of extinction by breeding the critically endangered species in captivity. Read Part Two here.
A baby Sumatran rhino displays the species’ characteristic shaggy fur. Photo courtesy of the Cincinnati Zoo.
The most endangered rhino is one you’ve probably never heard of. Unlike its more famous African cousins, the Sumatran rhino (Dicerorhinus sumatrensis)–sometimes called the hairy rhinoceros–has two horns and a variable coat of shaggy fur, especially on the ears. They’re smaller, solitary, and live in dense tropical forest. It’s not the first word that comes to mind when you think of rhinos, but if any rhino species is cute, this is the one.
Once widespread across Southeast Asia and the Himalayan foothills, hunting and habitat loss reduced Sumatran rhinos to just a few small populations by the end of the 20th century, prompting fears that without intervention the species would go extinct.
Husbandry and health
In 1984, when perhaps a thousand were estimated to be left in the wild, a program was initiated to take rhinos into captivity from habitat that was about to be destroyed. Forty Sumatran rhinos were captured in Indonesia and Malaysia with the hopes of starting a captive breeding program. Seven of these rhinos were sent to the US, three to the UK and one to Thailand, while seven remained in Indonesia and 22 in Malaysia. By the late 1990s, not only had there been no calves, but fewer than half of those animals were still alive. Some deaths were likely due to old age, but simply maintaining their health in captivity had turned out to be far more difficult than zoos had anticipated.
One very basic problem was diet. Many rhinos suffered from digestive problems until their caretakers realized the typical zoo diet for browsing species wasn’t suitable. “A primarily hay-based diet didn’t work,” Terri Roth of the Cincinnati Zoo, who led the research team that produced the first calf, told Mongabay. “With a lot of other browser species we can convert them to another diet in captivity, but these we can’t.” Fresh browse, in particular ficus, was crucial.
Terri Roth with one of her charges at the Cincinnati Zoo. Photo by Michelle Curley.
The rhinos were also prone to eye problems. “If you think of how they live in the wild, they’re in the dense forest, and they’re fairly sedentary during the bright daylight hours. They don’t get exposure to a lot of sunlight,” says Roth. However, they didn’t seem to have an instinct to avoid it, and their eyes would basically get repeatedly sunburnt, resulting in scarring and vision loss. Fortunately, the solution to this one was simple: “Once we built a big shade structure over the enclosure we didn’t have any more problems.”
Another health issue presented a much more serious challenge. Iron storage disease is a problem for a wide variety of species in captivity, from dolphins to tropical birds. While it’s not known for sure, Roth suspects it is a side effect of easier living in captivity. In the wild, she explains, animals absorb as much of the vital nutrient as possible because they eat a diet low in iron and lose blood from parasites and injuries. “We get rid of parasites, we keep them from fighting conspecifics so they don’t get injured…. We do all these things to make life better for them, and now they’re getting too much iron.”
Roth says there’s some future hope for treatment. Human medicine is developing oral drugs to treat the disease, and at some point it might be possible to use these in wildlife. “The challenge is right now those medicines are far too expensive, especially for something as large as a rhino.” In the meantime, animals crucial to the breeding program have been lost to the disease.
Relationship issues
Bull rhino Ipuh in his enclosure at the Cincinnati Zoo. Photo courtesy of the Cincinnati Zoo.
In the 1990s the last three Sumatran rhinos left in the US were brought together at the Cincinnati Zoo. At this point, early attempts at breeding had either failed or, worse, resulted in injuries.
Unlike African rhinos, Sumatrans are solitary in the wild. “We couldn’t house them together,” Roth says. “When we put them together, they’d fight.” So it was particularly important to know when the female was receptive before putting a pair together for breeding. However, nothing was known about their reproductive physiology, and the animals weren’t helping—there were no reliable behavioral signs. “We would have cycles where we could tell the day was right because the male was excited and spraying urine all over the place,” Roth says. “Other times they would be sleeping in adjacent stalls until we let them out and they started breeding.”
They couldn’t risk having these incredibly rare animals hurt one another. “So that’s when we decided we really needed some science to try to determine what was going on with the female reproductive cycle,” says Roth.
Some Science…
Every stage of each rhino pregnancy was carefully monitored by ultrasound. Image courtesy of the Cincinnati Zoo.
Before the science came the training. Because the work required frequent testing, anesthesia wasn’t an option. Instead, the rhinos were conditioned to allow blood draws from their ears and rectal ultrasounds. The latter might sound like a crazy thing to try to do to a rhino, but Roth says it was actually surprisingly easy. “I would rather do a rectal exam on a rhino than a cow,” she says. “They just don’t seem to mind it that much. They are much better about that than blood collection, because they don’t like needles.”
Now, finally, it should have been clear: They’d have the data they needed to see when the female came into estrous. Except that after eight months of monitoring, they still couldn’t.
“As scientists working with wildlife, we have to be honest that we don’t know what’s going on when we don’t know what’s going on,” says Roth. Since they had to admit that they could not tell when the rhino was ovulating, they decided to try something different. The team started to carefully introduce the two rhinos to each other every day. Working with what they knew about the animals’ behavior, they waited until mid-morning after the male had eaten and was settled down in his pool. The pair was put together for just twenty or thirty minutes with staff watching for the whole time.
“I think after about 42 days of doing that daily, one morning we put her out and the male came right out of the pool and started following her around and resting his chin on her and mounting her,” Roth says. “Two days later we did the ultrasound and she had ovulated.”
This turned out to be a huge and unexpected discovery: The Sumatran rhino was an induced ovulator. They hadn’t been able to tell when she ovulated because she hadn’t—the female needed some interaction with the male for ovulation to occur, instead of it happening spontaneously on a regular schedule. “This was completely unexpected in rhinos, because the theory at the time was that they all spontaneously ovulated,” says Roth.
Andalas, the first successful birth of the captive breeding program. Photo courtesy of the Cincinnati Zoo.
It’s a Boy!… eventually
That first mating and ovulation didn’t result in conception, but finally the team knew how to proceed. Another wrinkle they discovered in these rhinos’ unusual physiology was that they needed to breed before the ovarian follicle reached its maximum size. “If you let it continue growing, the female will go out of estrous and it won’t ovulate,” says Roth.
Putting everything together, scientists could now determine the right time to put the pair together for breeding, even in the absence of behavioral clues. But Sumatran rhinos never give you a break: The next thing Roth and her colleagues learned is that successful mating leads to actual pregnancy only a very small percentage of the time. The female conceived on the second mating, which was pretty lucky given that in the long run it took over 30 matings to get three calves. Then, she lost the first five pregnancies. Finally, with the help of hormone supplements, she gave birth to the calf they named Andalas on September 13, 2001.
Rhino calf Emi and her mother Suci in their enclosure at the Cincinnati Zoo. Photo courtesy of the Cincinnati Zoo.
You’ll see Andalas referred to as the first Sumatran rhino calf bred and born in captivity in 112 years. “He’s called that because there was a report that we believe is real of a female that gave birth in 1889 in the Calcutta zoo that was in captivity long enough that she had to have mated in captivity,” says Roth. The details of this birth are lost to history.
Cincinnati’s breeding pair ultimately produced three calves: Suci, a female, was born in 2004, and in 2007, Harapan, another male. In the meantime, the breeding program in their homeland was not having any success, and the male was suspected to be infertile. So in 2007, Andalas was sent to the Sumatran Rhino Center on Sumatra. Some doubted whether Andalas would be able to do what needed to be done. “Some people said, he was raised in a zoo, he wouldn’t know what to do,” says Roth. “He has done just fine.” In fact, Andalas has sired two calves with female Ratu, the first in 2012, a male, Andatu, and this past May, a female, Delilah.
Harapan, nicknamed Harry, was a great favorite with zoo visitors and staff. Photo by Michelle Curley.
Difficult Decisions
In 2015, Harapan was the only Sumatran rhino left in Cincinnati and therefore the whole of North America. Emi, the mother, died of iron storage disease in 2009, and Ipuh, the sire, one of the oldest Sumatran rhinos in captivity, died in 2013. A much more painful loss, their daughter Suci, the second calf born at Cincinnati, was also lost to iron storage disease in March 2014.
Cincinnati would have loved to get a mate for Harapan, but that wasn’t in the cards. According to Widodo Ramono, executive director of Yayasan Badak Indonesia (the Indonesia Rhino Foundation), part of the decision not to send more rhinos to the US had to do with the feeling that living in their home country was better for the health of the animals. There was concern about the loss of rhinos to iron storage disease and about the difficulty of providing a natural diet in a foreign country. At the Sumatran Rhino Sanctuary (SRS) facility in Way Kambas National Park, the animals are kept in enclosures in natural forest, where they’re moved around when the browse is used up. “The Sumatran rhino eats more than 200 species of plants,” he says. “We think the best solution is to keep the rhino as wild as possible.”
Cincinnati needed to make a hard decision. “It was clear that Indonesia was not going to send us any more rhinos,” says Roth. “Either we were going to keep an animal here to serve as an ambassador all his life, or he was going to go over there.” In October 2015, Harapan was moved to SRS so he could contribute to the continuation of his species.
Harapan traveled from Ohio to Indonesia in a giant crate. Photo courtesy of the Cincinnati Zoo.
Roth says the relationship with colleagues at SRS has always been strong – she’s traveled there nearly every year since 1999. “It was very important to us that our colleagues in Indonesia be successful,” she says. “But sending Harapan, which closed the door on our program, was hard on everybody.” Not only had the research program been a huge part of her professional life, there was just something about that rhino. “People loved that animal, more than any of the other rhinos for some reason. He was incredibly charismatic.”
The working relationship continues, though, and Roth will soon travel to collect Harapan’s semen for testing and banking. And there’s no question that although they were unable to continue the program in Cincinnati, it was a huge accomplishment. “If they had never come here, all that information about their reproductive cycles and how to breed them would probably still be a mystery,” she says. “But we were able to figure that out, and just as important, have been able to transfer that to their country of origin.”
This article initially stated that eleven rhinos, rather than seven, were transported to the United States. It has now been corrected. We regret the error.
