Answer: Count Their Tooth Rings

In a curious crossover between checking the age of a tree and checking the age of a bear, the most accurate way to do both is to count their rings. Specifically, in the case of bears, the best way to determine the age of a bear is to examine a cross-section of their teeth (the outer part of the root, called cementum) under a microscope and count the layers.

Much like trees go through periods of growth and rest that create the rings of their trunk, bear teeth also go through periods of growth and rest continuously over the course of the bear’s life. Every year a new lighter colored layer forms and during the bear’s hibernation period, a thin black layer forms.

Not only can you count the black lines to see how many years the bear has been alive, but you can also examine the spacing between them to learn about the bear’s general health including if it has given birth to and raised cubs. The growth layers on mother bears’ teeth are thinner during the years they have cubs because much of the calcium and nutrients that make up tooth growth go to nursing the cubs.

Obviously this method, as you would assume, is reserved for posthumous examination as, unlike trees, no bear would stand for such an invasive examination.