B. Aging studies. Each year as a polar bear grows, a thin layer of cementum is added to the outside of each tooth. Age can be estimated by examining a thin slice of tooth and counting the layers. To estimate the age of a live polar bear, researchers can extract one small, vestigial premolar tooth. 1.Adult polar bears have no natural predators.
Males occasionally kill other males competing for mates.
Males periodically kill females protecting cubs. 2.Cubs less than one year old sometimes are prey to adult male polar bears and other carnivores, such as wolves. 3.Newborn cubs may be cannibalized by malnourished mothers. D. Human interaction. Polar bears have been hunted for thousands of years.