We had a trip to the zoo this week to see a bear with a sore head - dental caries to be specific. A 1940 study (Hall ER) looked at 360 bear skulls and found caries in 3. This is an 0.8% prevalence.
Two were young adults and, as in our image, the occlusal surfaces were more severely affected. Berries and fruit are an important part of the diet. Berries have a low pH which can erode enamel. The other possible culprit is honey. This is a fermentable carbohydrate, which is necessary for caries formation.
Interestingly a similar study in polar bears found no caries - probably due to their strictly carnivorous habits.