A new study suggests that there are six, and not two, distinct subspecies of tigers remaining in the world. These findings, according to a report from the New York Times, could offer better guidance for conservationist groups hoping to save the endangered animal from extinction.
Prior to the new study, scientists originally believed that tigers can be classified into five subspecies. Gizmodo wrote that this changed in 2015 when researchers found that classifying tigers was as simple as dividing them into two subspecies — one found in the mainland, and another found in Sumatra and other Indonesian islands. In 2017, this two-subspecies system was recommended by the International Union for Conservation of Nature’s Cat Specialist Group as the ideal system for preventing tiger populations from further decline.
This guidance, however, was challenged by Peking University scientist and study lead author Shi-Jun Luo and her colleagues in a paper published Thursday in the journal Current Biology. Compared to 14 years ago, when Luo first presented her theory that tigers have six living subspecies, the team used newer and more advanced methodologies and genomic techniques to perform a genome-wide analysis of 32 preserved wild tiger specimens.
The new findings confirmed that there are six living tiger subspecies — Amur, Bengal, Indochinese, Malayan, South China, and Sumatran. Three other subspecies that were first identified in the 1930s — the Bali, Caspian, and Javan tigers — were found to have gone extinct within the last 70 years.
As noted by the New York Times, there are fewer than 4,000 tigers currently surviving in the wild. This is a figure that is drastically lower than the estimated 100,000 tigers that lived about a century ago before human-driven factors such as poaching and habitat destruction caused their numbers to dwindle. One subspecies, the South China tiger, only exists in captivity at the present.
The researchers also discovered that all tiger subspecies most recently had a common ancestor about 110,000 years ago, with this creature believed to have existed in what is now known as Southeast Asia and southern China. This was the time the species was believed to have spread out to other parts of Asia due to a population collapse that was driven by climate change.
Due to this population collapse, all living tiger subspecies have their own genetic characteristics that set them apart from each other. These include Sumatran tigers, which were the first to diverge from their common ancestor and have genes that allowed them to develop smaller bodies than other subspecies.
“In India and Siberia, tigers prey on large ungulates, but in Sumatra, they rely more on wild boar and smaller deer. It makes sense that smaller prey would exert selection pressure for smaller tigers,” said Luo.
In a statement quoted by the New York Times, Luo said that her team’s work is important because saving the genetic diversity of tigers is just as essential as preventing the animals from going extinct.
“To preserve such genomic signatures is to preserve evolutionary uniqueness that tigers have accumulated over thousands of years. We need to respect this uniqueness by maximizing our efforts for all tiger subspecies.”
While Luo and her team believe that reclassifying tigers into six subspecies could be more beneficial than the previous two-subspecies system, other experts feel that the use of advanced techniques to analyze the tiger’s genome won’t make a big enough impact in the quest to save all subspecies from extinction. Ullas Karanth from the Wildlife Conservation Society told the New York Times that the populations of certain subspecies, specifically the Indian and Russian tigers, are “just too small” to be saved through reclassification.