Cave bears' inflexible eating habits might have led to their demise, a new study suggests.

The ancient bears, which went extinct about 25,000 years ago and stood as tall as 5.5 feet at the shoulder, may have eventually perished because they followed a vegan diet, according to the study.

Scientists analyzed cave bear bones from a Belgian cave, and found that the prehistoric ursines were herbivores. Modern-day brown bears eat lots of things: their omnivorous diet ranges from fish to mammals to plants. But cave bears might have been narrow-minded when it came to their dining decisions. 

"The Cave Bear is a very different story [compared to brown bears]," Dr. Hervé Bocherens, of the Senckenberg Center for Human Evolution and Palaeoenvironment in Germany, said in a statement. “According to our newest findings, these extinct relatives of the Brown Bear lived on a strictly vegan diet."

Bocherens compared the eating habits of the cave bears to modern-day giant pandas, which are also inflexible eaters.

“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,” he said in the statement.

The results were published in the Journal of Quaternary Science.

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