TüBINGEN, Germany, Aug. 23 (UPI) -- Stretching nearly 12 feet in length and rising more than 5 feet tall, Europe's cave bears, Ursus spelaeus, were even larger than their closest modern relative, the brown bear.
But as new research proves, their size wasn't bolstered by a diet rich in protein. No, the hefty cave bear was a vegan. The new study -- published this week in the Journal of Quaternary Science -- suggests the inflexibility of its herbivorous diet was the species' undoing.
By around 400,000 years ago, cave bears had established populations across a range stretching from Northern Spain to the Ural Mountains. Their reign ended around 25,000 years ago. Though its time on Earth was relatively short, the species left thousands of bones for study in the caves of Europe.
Recently, a team of international scientists set out to scavenge those bones for clues to why they disappeared.
"We were particularly interested in what exactly the cave bears ate, and whether there is a connection between their diet and their extinction," lead study author Hervé Bocherens, a biogeologist at the University of Tübingen, explained in a news release.
Analysis of isotope levels in collagen extracted form the ancient cave bear bones suggests the species subsisted on a strictly vegan diet.
"Similar to today's giant panda, the cave bears were therefore extremely inflexible in regard to their food," Bocherens added. "We assume that this unbalanced diet, in combination with the reduced supply of plants during the last ice age, ultimately led to the cave bear's extinction."
As the climate shifted across much of Europe, the bears ran out of a suitable supply of food.
Previously, scientists have speculated that the cave bear lost out to increased human hunting pressure and extremely cold temperatures.