Early bears were omnivores: Three-dimensional jaw analyses reveal diet

Ursus minimus – presumed to be the common ancestor of most modern bear species – lived in Europe between 4.9 and approximately 1.8 million years ago, during the Pliocene epoch and possibly into the early Pleistocene. The species represents the first black bears in Europe and the oldest known representative of the genus Ursus, which also includes today's brown and polar bears. Until now, researchers assumed that the ancient bear fed mainly on insects. A new study by SNSB zoologist Anneke van Heteren now paints a different picture: Ursus minimus, the so-called Auvergne bear, was most likely a typical omnivore – with no particular preference for insects. For her research, the mammal expert compared the jaws of Ursus minimus to those of other recent and extinct bear species with a range of diets – including specialists such as the insectivorous sun bear, the carnivorous polar bear, and the strictly vegetarian giant panda. The bear jaws have differing biomechanics when chewing food, depending on diet. Different jaw opening angles and the position of the chewing muscles reveal the animals' eating habits. The researcher from Munich used geometric morphometrics for her study. This involves measuring skeletal parts using digital measuring points, known as landmarks. This 3D shape analysis allows the jawbones of the bears to be visualized in three dimensions and compared using statistical methods.

"As a true omnivore, Ursus minimus was particularly flexible and adaptable and could easily adjust to changing food availability. This general adaptative strategy might have been the basis for the later evolution of specialized diets in other bear species. The findings on the dietary habits of such primitive species like Ursus minimus provide new insights into our understanding of the evolution of bears and their adaptability to changing environmental conditions," explains Anneke van Heteren, Curator of mammals at the Bavarian State Collection of Zoology (SNSB-ZSM) and author of the study.

Most modern as well as extinct bear species - with their entire range of different diets - can be traced back to the very primitive Ursus minimus.