This concept makes me really, really want to show a talk my grandfather did to some Japanese biologists and the reaction they had about considering ourself as the same level of animals in the circle of life. It's an idea that exist all over the world though, that humans are somehow above animal behavior makes it difficult for people to conceptualize how animals actually feel. Both expecting them to have the same social structures as humans but also not thinking that they are intelligent enough to be beyond helpless and innocent.
The whole idea that the bear might return to take revenge for it's mother, that is really interesting to me. I ranted before but spite is a trait that really is not something that can theoretically be an evolutionary advantage as an animal that practices true spite will not live to pass that gene down, but working with some animals I've seen personally that it still pops up. Altruism is probably more what the deer was showing, but a more diluted form because it was for it's kin. And in that same thought Touma was showing true altruism himself by sacrificing his life for a stranger. I do wonder if that was the intention behind this arc
Idk. I love this series, it made me depressed a lot but also a bit hopeful