A mysterious huge giant rhino species – called the Siberian unicorn because of its huge single horn – appears to have survived in Western Russia until 36,000 years ago, according to research published today in Natureology and Evolution. This eradication date means that the last days of the Siberian unification were shared with early modern people and neanderthals.
Previously, little was known if the creature believed to have been extinct more than 200,000 years ago. But genetic analysis and radioactive dating have begun to reveal many aspects of how it lived, and when it died.
An important result is that the Siberian unicorn was not extinct due to modern human hunting, not even the peak of the last ice age that began about 25,000 years ago.
Instead, it led to a more subtle change in the climate which reduced grasslands from Eastern Europe to China.
Our new findings show that the Siberian unicorn was dependent on these grasslands and, unlike other species in the field of saiga antelope, could not adapt to changes.
The "Siberian Unicorn"
The Siberian unicorn (Elasmotherium) had one large horn, estimated up to one meter in length. It was one of many different rhino species that once existed.
In addition to the extinct molluscs (still available as frozen mummies) there are five species of live rhino. All of these creatures are unfortunately now in trouble, including the White Rhino (near threatened), Javan-Rhino (critically threatened) and Sumatran rhino (critically threatened).
The loss of the Siberian unicorn provides a valuable case study that shows the wrinkles' poor resistance to environmental change.
The animal we worked with was found in modern Russia, although its scope was also extended to areas now comprising Kazakhstan, Mongolia and northern China, where it inhabited a steppe-like habitat dominated by grass and herbs.
The Siberian unicorn shared this environment with saiga antelope and other ice eels including wool rhino and mammoth.
But most of the evidence so far suggested that the Siberian unicorn was extinct 200,000 years ago, while the woolen nuns and mammals were killed about 13,000 and 4,000 years ago.
So why was the Siberian unicorn extinct while other species living in the same habitat lived for thousands of years longer or, like saiga, are still surviving today?
A smoke gun
Some unconfirmed evidence has recently suggested that the Siberian unicorn survived until closer to the present, much like the woolen hides. So we examined the age of 23 bone samples of the animal held in museum collections in Russia and the United Kingdom.
Rather than 200,000 years, new dating found that the Siberian unicorn was actually eradicated just recently 36,000 years ago.
Next, we felt how it might have been extinct at this time.
Climate change seems to be a likely competitor – but 36,000 years are well ahead of ice age, which occurred 20,000-25,000 years ago.
But this date matches the timing of a pronounced change towards cooler summers across northern Europe and Asia. This seasonal change resulted in grass and herbs becoming more sparse and an increase in tundra plants like mosses and lichens.
A vulnerable specialist
So why has a climate change 36,000 years ago pushed the Siberian unicorn out, but not the wool rhino or saiga?
To answer this question, our survey took fossil bones from the Siberian unicorn, the ephod and saiga and watched the nitrogen and the carbon they contained – because the differences in these elements reflect an animal's diet.
We found that 36,000 years ago, the saiga and Siberian unicorn behaved the same way and eat grass almost exclusively. After this point, carbon and nitrogen in saiga bones showed a big dietary change to other types of plants.
But shifting from the grass diet proved to be difficult for the Siberian unicorn, with its special folded weary teeth and a low-heeled head at the grassy height. Relatives like the eardrum had always eaten a more balanced range of plants, and were less affected by a change in habitats.
Importantly, the climate change that drove the Siberian unicorn was actually much less pronounced than those that occurred during the Ice Age that followed. Or the changes that we will meet in the near future.
The story of the Siberian unicorn is an early reminder that even subtle changes in plant distributions can have devastating knock-on effects for large animal species.
Surprisingly, this is a major risk to many animals, such as the surviving cousins of the Siberian unicorn, which, thanks to people, already have very limited areas.