If you look closely, you’ll notice that these black bears are not American black bears. They are Asiatic black bears that have had their manes trimmed back.
Of they are hybrids between Asiatic and American black bears.
Asiatic black bears were more commonly used in circuses and Hollywood because they were more docile and easy to train.
Of course the narrative is a bit off. American black bear sows with cubs are among the least dangerous of bears. A female black bear may defend her cubs, but all she will likely do is take a nip or a swat. It’s the male bears that actually prey upon people that should be of greater concern. Nearly all fatal attacks from American black bears involve predatory behavior from males, as this recent study confirmed.
Yeller likely didn’t save Arliss’s life, but he did save him from a nasty bite or scratch.
This scene is also a reminder that the black bear was once a part of life in the Texas Hill Country. Maybe it will be again someday, according to this:
http://www.wildlifemanagementpro.com/2008/04/18/black-bears-on-the-move-in-texas/