The lecture discusses the short-faced bear and gives three reasons why it is unlikely that the short-faced bear was a carnivore and more likely that it was an omnivore and scavenger. The lecturer's points go against the points made in the reading.

First the lecturer points out that nitrogen-15 testing is not 100 percent conclusive in proving that the short-faced bear was a carnivore. He points out that an omnivore that ate a lot of meat as well as a lot of plants would also have a high nitrogen-15 to nitrogen-14 ratio.This disputes the reading's claim that the short-faced bear was a carnivore because testing showed a high ratio of nitrogen-15 to nitrogen-14 in bear remains.

Second, the lecturer mentions that the environment of the bear is an important consideration in diet. The polar bear lives in an Arctic Ocean environment that doesn't include plants, so that is why it is a carnivore. The environment of the short-faced bear included plants so it probably ate a lot of plants. The two bears are similar, but their diets are probably different because of their environments. This contradicts the reading's claim that the short-faced bear's great size means it must have been a carnivore.

Thirdly, the lecturer agrees with the reading that the legs and the claws of the short-faced bear would have been good for running. But the lecturer points out that these structures are more efficient for slower, long-distance travel. Therefore, the lecturer concludes that the short-faced bear was more likely to have used its long legs to travel over long distances in search of a variety of foods. This casts doubt on the reading's claim that the short-faced bear's leg structure allowed it to chase down and attack large animals to feed a carnivorous diet.