for National Geographic News
How do you make a 4,000-pound (1,800-kilogram) rhinoceros disappear?
That's the weighty mystery facing a Nepali nature reserve where more than four dozen Indian rhinoceroses have gone missing over the past several years.
Starting in the 1980s wildlife officials introduced 72 of the rare rhinos to a protected valley about 200 miles (320 kilometers) southwest of Nepal's capital city of Kathmandu as part of a conservation program.
"We have records showing 23 rhinos had died due to poaching or other causes. The rest are missing," Laxmi Prasad Manandhar, a senior official at Nepal's Department of National Park and Wildlife Conservation, told the Reuters news service.
"Where did they go? I have no answer. It is a mystery," Manandhar said.
The Indian rhino, also known as the great one-horned rhino, once roamed wild in the Babai Valley, which was made part of Royal Bardia National Park in 1984 (related photo: baby Indian rhino born in California zoo [February 11, 2005]).
The species is also found in the wild in the northeast Indian state of Assam.
In Nepal, army units stationed inside the national parks once effectively deterred poachers and helped the country's rhinos rally from about 60 animals in the mid-20th century to more than 500 in 2000.
But Nepal's recently ended civil war hampered conservation efforts and fueled the poaching of rhinos and other wildlife (photos: inside Nepal's revolution).
The monarchy's troops were needed to battle Maoist rebels, so the parks were left unguarded and poachers were free to ply their trade.
Royal Chitwan National Park, Nepal's largest rhino stronghold, has seen its population fall from 544 of the animals in 2000 to 372 in 2005.
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