Sometimes, they simply shoot the beasts dead, even though the horns can grow back within two years without harming the animal if carefully cut. Officials and nonprofits in South Africa are preemptively cutting some rhinos' horns in an attempt to save them, but some poachers are killing anyway just for the nubs.
Vietnam wiped out its own last known Javan rhinoceros in 2010, despite the country's earlier efforts to protect it. The last of the population was found dead in a national park, shot through the leg with its horn hacked off.
Tran Dang Trung, who manages a zoo outside Hanoi that imported four white rhinos from South Africa, said he worries for the animals' safety even though the zoo has 24-hour security.
"If thieves wanted to kill the animals and steal their valuable parts, they could," Trung said recently outside the rhinos' basketball court-sized outdoor pen.
Laws in Vietnam surrounding the business of importing horns are murky and crackdowns are rare despite government pledges to root out traffickers.
Officially, no more than 60 horns are legally imported into Vietnam as trophies bagged from South African game farms each year, but international wildlife experts have estimated the actual number of trophy horns taken by Vietnamese nationals from South Africa each year may exceed 100.
Earlier this week, the South African government said it was working with the Vietnamese to stop the potential abuse of hunting permits. Hanoi has also been asked to conduct inspections to make sure rhino trophies imported from South Africa still remain in the hunters' possession.
It's impossible to track how other rhino horns are entering Vietnam, wildlife advocates say, but they point to local media reports suggesting Vietnamese diplomats are implicated in the international trade that's been largely banned since 1976.
In 2006, a diplomat at Vietnam's South African Embassy was arrested for trafficking rhino horn, while another was filmed two years later trading the substance outside the mission's gates. A third diplomat was also questioned that same year after 18 kilograms (40 pounds) of rhino horn was found in his car outside a casino.
In a statement, Foreign Ministry Spokesman Luong Thanh Nghi said those incidents reflected badly upon Vietnam's image, and that the diplomats all faced disciplinary measures.
Meanwhile, illegal rhino killings in South Africa are skyrocketing — from 122 in 2009 to 333 in 2010 and a record 448 in 2011. The country reported last week that 150 rhinos had already been poached this year, nearly 60 percent taken from Kruger National Park.
In Hanoi, Vietnamese buy rhino horn on the streets of the city's bustling old quarter, where a traditional medicine dealer recently told the AP that the average prescription costs 200,000 dong ($10).
Hanoi doctors report that some of their clients take the powder as a supplement to western medicines, believing it cures fever and other common ailments. Others use it as a last-ditch effort against cancer.
Nguyen Huu Truong, a doctor at Hanoi's Center for Allergy Clinical Immunology, said a handful of patients visit him each year complaining of rashes he links to rhino horn consumption.
"Many Vietnamese believe that anything expensive is good, but if you're going to spend a lot of money on rhino horn, you might as well bite your nails," he said. Rhino horns are composed of keratin, a protein found in human hair and fingernails.
Giang, the young Vietnamese woman who regularly uses rhino horn to prevent hangovers, says she's unfazed by doctors' assessments of the substance's efficacy and doesn't care to know how her father acquired the horn.
Experts say some rhino horns passing through Vietnam are fakes, and the AP couldn't verify the authenticity of Giang's horn, which she grinds on a plate with a rough finish made specifically for the task. She ingests the liquefied form when she has allergic reactions or after tippling on too much top-shelf liquor.
Because Giang only takes rhino horn shots once or twice every three months, she estimates her horn will last another 10 to 15 years. But once her stash is depleted, there may not be any rhinos left on earth to satisfy her craving.
Associated Press writer Donna Bryson in Johannesburg, South Africa, contributed to this report.
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