Bears is a much more straightforward nature movie than you might expect. The story of a pair of brown bear cubs and their mother through their first year together, it doesn't try to escape the inevitable cuteness of bear cubs, but except for that, it does not present the life in nature as being cute at all.
In fact, it's a pretty grim battle against starvation in a wild world where you have to know where you're going and have to get there at the right time or there will be no food-- even for animals that can eat everything from grass, to clams, to shellfish, to, unfortunately, each other.
Papa Bear is never even mentioned, and what males are around would love to feast on the cubs if they can get past Mother, though anybody who has had dealings with her is hardly eager for a repeat experience.
We are told that half of all newborn bear cubs do not live to see their first birthday. And, formidable as she is, Mama is susceptible to exhaustion and despair, and her kids are about as much help as you would expect kids to be, especially her son.
There is some gender stereotyping between the son and daughter, but Ma is too busy and worried to show much personality, and the other characters-- all animals and no CGI-- are pretty two-dimensional obstacles to the little family's survival. And we are told that this is just the first of three such years.
Bears is not as grim as March of the Penguins, but its portrayal of the cruelty of nature is apparently not what some people expect from the Disney studio, people who forget that even in Bambi, Disney let Bambi's mother dies at the hands of a hunter.
Refreshingly, there is no depredation by human beings, although I recommend that you not consider that people are threatening the salmon without which the bears would have virtually no chance at all.