A new study may settle a long-standing debate about the origin of Borneo's elephants. Tradition holds that elephants were introduced to Borneo as a gift to the Sultan of Sulu around 250 years ago. But now, new genetic data provides compelling evidence that the elephants may be a distinct population, isolated when Borneo was cut off from the mainland as long as 18,000 years ago.

The finding is significant because it makes Borneo's 2,000 or so Asian elephants (Elephas maximus) one of the highest priority populations for conservation.

"Genetic studies continue to provide data that contradicts what we think we know about nature," said Lori Eggert, conservation geneticist at the Smithsonian Institution in Washington, D.C. "A population once considered feral, has become one of high priority for conservation."

Popular Belief

Borneo's few thousand elephants are restricted to a small pocket of habitat in the island's northeastern corner. This "limited and unusual distribution," along with the common belief among locals that the elephants were recently introduced, suggested that Borneo's elephants weren't indigenous, said Prithiviraj Fernando, a conservation biologist at Columbia University in New York City.

Fernando is lead author behind the new study, which will be published later this fall in the science journal Public Library of Science Biology.

Borneo's elephants were classified as separate sub-species in 1935. But researchers later reclassified the elephants as members of either the Sumatran or Indian sub-species on the premise that they weren't morphologically, or physically, distinctive enough to warrant a separate grouping.

Little historical evidence has been available to arbitrate in the debate. There is almost no written record of Borneo's elephants before the 18th century. The only existing fossil is a single elephant tooth from a cave in Brunei.

Local tradition holds that the East India Trading Company gifted Indian elephants to the Sultan of Sulu (a nearby island) in 1750.

According to that legend, the Sultan had the elephants released in Borneo, which fell under his rule, and Borneo's elephants today are their descendents.

"It is possible that some elephants were gifted to the sultan, and he did send them to Borneo," said Fernando, "[The notion] was picked up by some writers and got propagated." Many experts never believed that this was the complete story.

Genetically Distinct

Fernando, Columbia University biologist Don Melnick, and a group of researchers in the United States, India, and Malaysia set out to settle the debate once and for all. The team gathered two different types of DNA samples from local elephants, and compared it to DNA taken from animals across the Asian elephant's range, including Sumatra, Peninsular Malaysia, and India-three likely possible sources of introduced elephants.

The analysis showed that, while Borneo's elephants bear most similarity to elephants from Malaysia, they are genetically distinct from all Asian elephants. "If Borneo elephants were introduced, they would not have had time to become genetically distinct from the source population [in just 250 years]," said Fernando.

The most probable explanation is that the animals became isolated from those on the mainland 18,000 years ago when the last land bridges disappeared under rising sea levels. However the genetic differences are great enough to hint that Borneo's elephants may have been a distinct population for as many as 30,000 years, says the report.

The results of this analysis "are very tight in my opinion," said Samuel K. Wasser, a conservation biologist at the University of Washington in Seattle. The elephants "likely came over on a land-bridge present during the glacial periods of the Pleistocene," when sea levels were lower, he said.

Conservation Priority

The elephants should now be considered a conservation priority, "representing an important extension of the Asian elephants' known range," said Wasser. The find extends the natural range of the Asian elephant by 1,300 kilometers (800 miles).

Conservation projects are now essential. "The whole population is only a couple of thousand animals," said Fernando. "There is widespread habitat loss in Borneo, and there are very few captive animals."

Finding that these elephants are unique and have been isolated for at least 18,000 years, means that elephants from other regions shouldn't be introduced, as they may not share adaptations to local conditions, observed Eggert, the Smithsonian conservation geneticist. "These animals have co-evolved with parasites and pathogens, as well as local food plants," she said. "Introducing outside animals could disrupt those adaptations."