Sumatran rhinos have hairy coats and tufted ears, ancient features that lead biologists to conclude they are among the oldest surviving rhinos. They are small, about eight to nine feet long and three to four feet high at the shoulder, but the Bornean rhino is slightly smaller and its skull is shaped somewhat differently, said Juan Carlos Morales, an associate research scientist at Columbia who performed much of the genetic analysis. Like almost all species, rhinos have been classified by physical characteristics, not genetic differences, and the Bornean rhino has been recognized as a separate subspecies since 1965. Now found only in Sabah state, it has been separated from its Sumatran cousins for at least 10,000 years by water and probably longer by mountains. Although timber extraction has resulted in loss of rhino habitat on Borneo, poachers have taken a far greater toll.
Poachers seek rhino horns for ornamental dagger handles and purported medicinal benefits.
The Columbia study will be a valuable tool for government conservation officials in Malaysia and Indonesia, said Thomas Foose, program officer for the International Rhinoceros Foundation in Cumberland, Ohio, which is working with local governments to preserve rhinoceros populations around the world. The study provides a detailed map of the Sumatran rhino's genetic diversity, information that could not have been provided without genetic analysis techniques developed over the last decade, Professor Melnick said. Co-authors of the research with Drs. Researchers examined the DNA in cell bodies called mitochondria, because such DNA evolves relatively rapidly, making it a good indicator of recent genetic changes. They used enzymes that cleave the animals' DNA at specific sequences of base pairs, then compared the resulting fragments for genetic similarity.