The Javan rhinoceros is extinct in mainland Asia, conservationists announced this week.

An adult female Javan rhino was shot and killed in a Vietnamese forest last year—leaving just one wild population left of the species in the world, a group of fewer than 50 individuals in a small park in Indonesia.

"The last Javan rhino in Vietnam has gone," Tran Thi Minh Hien,Vietnam director of the nonprofit WWF, said in a statement. (Watch a video of the Javan rhino's road to extinction.)

Watch a video of the last Javan rhinos in Vietnam.

In April 2010 park rangers discovered the remains of the female rhino, which appeared to have died only a few months before.

"A veterinary pathologist estimated that the animal was an adult—but not elderly—individual, probably 15 to 25 years old," Nick Cox, manager of WWF's Species Programme in the Greater Mekong, said in an email.

A DNA comparison of skin taken from the corpse and from nearby rhino dung showed the DNA belonged to the same individual—quashing hopes that there might have been more than one rhino in the area. Poaching was the likely cause of death, WWF said, as a bullet was found in the animal's leg and its horn had been removed.

The horn of the Javan rhino is highly prized in Vietnam and China, where it's ground into a powder and sold as a purported cure for ailments such as fever, arthritis, high blood pressure, and cancer.

Rhino Conservation Hopes Dashed

According to historical records, herds of Javan rhinos once roamed Southeast Asia, and the animals were plentiful enough to be considered agricultural pests. (Watch a video of a Javan rhino in Indonesia.)

But habitat loss and widespread hunting slashed their numbers, so that by the latter half of the 20th century, the animal was believed to be extinct on mainland Asia.

In 1988, a population of 15 or fewer individuals was found in the Cat Tien region of Vietnam. Conservationists were hopeful that this population, though tiny, could recover, based on the success of Africa's southern white rhino.

Southern white rhinos had been poached to only about 20 individuals by the late 19th century, but due to intense conservation efforts, the population now numbers close to 20,000 animals.

Hopes were dashed, however, when a 2004 survey suggested that the Cat Tien population had been reduced to two individuals, both of them female.

A more thorough survey involving dung-sniffing dogs in late 2009 and early 2010 turned up 22 fecal samples, but a DNA analysis showed the droppings had been left by only a single individual. Sometime between 2004 and 2009, one of the rhinos had died or been killed—leaving only the female found dead in 2010.

Rhino Extinction a Wakeup Call for Vietnam

Conservationists are sure that no more Javan rhinos exist in Vietnam.

"We thoroughly searched the only area that has supported a rhino population in the last 20 years," Cox said.

The animal's local extinction should be a wakeup call to Vietnam to protect its other endangered animals, such as tigers and elephants, he added. (See "Pictures: Hundreds of Rare Gibbons Found in Vietnam.")

"It's a question of mourning the loss but making sure we learn the lessons, and creating an even greater sense of urgency for those species that still remain," Cox said.