To determine the bears’ bite forces, the researchers reconstructed their jaw muscles and analysed their cross-sectional areas. In addition, they analysed the microstructures of the bones to determine muscle fibre density. The researchers then used computer models to calculate and compare the bears’ bite forces.
The model estimated that cave bears could exert maximum bite forces of about 1,200 newtons (N) at the canine teeth and about 1,700 N at the molars. Brown bears, by comparison, could generate maximum forces of about 1,600 N at the canines and about 1,950 N at the molars.
“Although cave bears had slightly lower maximum bite forces than brown bears, they were still able to break open tough food items, such as bones, and consume nutritious bone marrow,” says first author Dr. Stephanie Müller of the University of Mainz.
However, the researchers also found that cave bears had greater leverage at their molars than brown bears. This would have allowed them to grind plant matter more efficiently. “This indicates that cave bears had a more herbivorous diet than brown bears,” says Müller.
The researchers suggest that the difference in diet between cave bears and brown bears may have been a key factor in the former’s extinction. Following climate change approximately 125,000 years ago, plant productivity in Europe declined significantly. Cave bears were likely more affected by the deteriorating food conditions during this period than brown bears were, leading ultimately to their extinction about 25,000 years ago.
“Our study shows that competition for food was likely a major factor in the extinction of cave bears,” says Müller. “By analysing the bears' jaw muscles and computer modelling, we have been able to gain new insights into their diets and the challenges they faced during the late Pleistocene.”
