An international team of researchers discovered that the Sumatran rhinoceros, currently on the brink of extinction, may have already been critically endangered far longer than what was previously thought.

Statistics reveal that the Sumatran rhino is one of the rarest animals in the world, with fewer than 100 remaining. The species, which was once endemic to several countries in Southeast Asia, was declared extinct in the wild in Malaysia in 2015.

The Truth Behind The Sumatran Rhino Extinction

Scientists have sequenced the entire genome of the Sumatran rhino for the first time. The sample was from Ipuh, the male Sumatran rhino who lived in captivity at the Cincinnati Zoo for over decades until his death over four years ago.

The findings, which were published in the Current Biology journal, revealed that the Sumatran rhino had been facing extinction for quite some time.

"Our genome sequence data revealed that the Pleistocene was a roller-coaster ride for Sumatran rhinoceros populations," said Herman Mays Jr., a genetics professor at Marshall University and the lead author of the study.

The Pleistocene era spanned the period from 2.6 million to 11,700 years ago. It was within this time that the population of many large mammals, including the Sumatra rhino, reached their peak.

However, as the Pleistocene ended, the population of the large mammals dwindled. Scientists estimated that 9,000 years ago, the Sumatran rhino population fell to just about 700, and the species never fully recovered.

What Pushed The Sumatran Rhino To The Brink Of Extinction?

To study the history of the Sumatran rhino, scientists used the pairwise sequentially Markovian coalescent technique. Through PSMC, they were able to use the species' genome sequence to estimate the demographics of the Sumatran rhino over the past thousands of generations.

After thorough analysis, the conclusion of the researchers is that it was climate change that negatively affected the original habitat of the Sumatran rhino in the biogeographical region known as Sundaland in Southeast Asia. Sundaland was submerged after weather events that happened at the end of the Pleistocene era, causing the species to be fragmented and resulting in its decline.

Man, however, still played a part in the fall of the Sumatran rhino into an endangered species. As the species struggled to recover, hunting and deforestation contributed to a quick decline of the Sumatran rhino population.

"The Sumatran rhinoceros species is hanging on by a thread," said Terri Roth, a researcher from the Center for Conservation and Research of Endangered Wildlife at the Cincinnati Zoo and Botanical Garden.