Competition for food? Jaw analyses show what cave bears and brown bears ate

The differences lie in the details. Recent 3D shape analyses of the jaws and dentitions of cave bears and brown bears coexisting in the site of Goyet caves in Belgium reveal distinct differences in their dietary choices.

The study, published in the journal Boreas, compares the diet of brown bears living approximately 30,000 years ago with their present-day North American relatives. The brown bear Ursus arctos is the closest living relative of the extinct cave bear Ursus spelaeus, which vanished about 25,000 years ago. These two bear species lived side by side in the same regions, including the Namur region of Belgium, between 1.3 million and 25,000 years ago. It is likely that they competed for plant food. The caves of Goyet and Trou des Nutons contain remains of both bear species dating back approximately 30,000 years.

Anneke van Heteren, mammal curator at the Zoologische Staatssammlung München (SNSB-ZSM), and her colleague Mietje Germonpré from the Royal Belgian Institute of Natural Sciences (RBINS) conducted this new study, which demonstrates that the two contemporaries had distinct feeding habits. The cave bear was strictly herbivorous, while the brown bear, then and now, is an omnivore. Notably, there are significant differences in the shape and biomechanics of their jaws.

The research team also identified slight differences in the jaws of fossil brown bears compared to their modern counterparts. According to van Heteren, “Presumably, the fossil brown bears from Belgium consumed slightly more plant-based food compared to the brown bears in present-day North America.”

Furthermore, the researchers examined cave bear cubs from Belgium and found that their jaws were less suited for chewing solid food compared to adult cave bears. Van Heteren speculates that the young bears may have still been nursing from their mothers. Their jaws needed time to adapt to the development of their permanent dentition.

Geometric morphometrics, a method that employs measuring points called landmarks to measure skeletal parts, allowed the team from Munich and Belgium to observe and compare the three-dimensional jawbones of both bear species using statistical methods. This revealed distinct biomechanical differences in their chewing movements.