Although bears are often classified as carnivores most bear species are classical anatomical omnivores. Their individual diets can range from almost exclusively herbivorous to almost exclusively carnivorous, depending on what kind of food sources are available to the animal both locally and seasonally, but primarily 70-80% of a bear’s diet is usually plant based. Bears cannot digest fibrous vegetation well and it is because of this that they are highly selective feeders. Their diet usually consists mainly of lent herbage, tubers and berries. Some scientists are even led to believe that because vegetation is not available in cold northern months, that this is why most bears hibernate during the winter.
Polar bears are considered carnivores but they will sometimes eat plants. However they mainly feed off of seal blubber, interestingly enough they hibernate during the summer months when seals are unavailable. Pandas are herbivores, while giant pandas have been known to eat some meat such as insects. About 90% of the eastern black bear’s diet consists of leaves, plants, grasses, buds, flowers, mushrooms, berries, fruits, nuts, acorns, and insects.
Although bears do mainly eat from plant based food sources, they do have a few anatomical features that are consistent with a carnivorous diet as well. For instance, the jaw joint of bears is in the same plane as their molars. The temporalis muscle is massive, and the angle of the mandible is small corresponding to the limited role the pterygoid and masseter muscles play in operating the bear’s jaw.
Bears also have short, small intestines and also like that of pure carnivorous animals exhibit a colon that is smooth, simple and short. What is interesting is that even though bears have the incisors, large canines, and premolars similar to those of other carnivorous animals, they have adapted molars that have become squared with rounded cusps for crushing and grinding, but yet still have not evolved to possess the blunt nails seen in herbivores. Instead they are still seen sporting the elongated, pointed claws of a carnivore.
Sometimes it can be confusing business when trying to figure out what exactly makes a bear carnivorous and what makes it omnivorous. At the end of the day, they can almost be classified in different ways as both or either/or. Really take your pick. It depends on the bear type, the location, the season, the food sources available, etc.