I think it was from a PBS documentary or some other “behind the scenes” show where one of the wildlife photographers described a scene where a bear killed a younger, smaller female to mate with the other one. I don’t know if its supposed to be some sort of threat or a show of might or what.
I’ve seen other shows where, yeah, a mother with cubs are avoiding other males like they were predators. 
Nature is pretty dark when you learn about the nitty gritty. Most of the deaths come hard.
