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I have heard and read from a few experts on the subject of animal behavior. Namely biologist. The believe that humans have impacted the behavior of animals through our interactions over the years. Well, not just humans. They're constantly adapting really. To their environment, to other animals, and of course, to us.
For example, perhaps due in part to the extinction of wolves in much of North America (up until their re-introduction a few decades ago from Canadian wolf packs into parts of Wyoming, Montana, etc) coyotes had moved up in the food chain. They didn't start forming large parks, triple in size and start taking down Caribou or anything crazy like that in the last one-hundred years, but they've become more wolf like then previously. Before wolves came back to Yosemite, they acted different then their cousins in Canada. They would form packs and take on larger prey. They were bolder and kept less to the shadows. When wolves came back, their coyote numbers were more than halved. And they became more solo again. I bring this up as an example that animals adapt and adapt quickly.
For a long time now, up until around the turn of the twentieth century, humans were a predator to be avoided by animals. The scents, sounds, and sight of humans was enough to deter a dangerous animal. Sure maybe you were unarmed while taking a walk around the wilds of Wyoming in 1860, but the Grizzlies and Wolves didn't know that. Through years of dealing with the natives and later trappers and mountain men, they knew enough to not take chances when humans were around.
That memory stayed ingrained with them even after their hunting became illegal. But it's been lessened as the years have gone by. Years have gone by where they have had interactions with humans were no harm was brought to them. The smell of a campfire no longer registers as dangerous humans nearby who might turn them into a rug. To a black bear, it means an easy meal at night when they are asleep and not tending to their food. Mountain lions accustomed to joggers running by unwary of their hidden presence may one day decide to make a meal of one if times get lean. As for Grizzlies, maybe they see us a nuisance, a threat to their cubs, or simply a potential meal. But they don't fear us.
Even wolves attacks, still considered very rare (in fact I'm not even sure there has ever been an officially recorded fatal attack on a human) have recently happened. I read in Canada or perhaps Michigan where some wolves came into a tent and dragged a child from his hair. He screamed, the parents woke up and managed to kick and fight the wolves off. Same with a lone female jogger in Australia being attacked by several dingos.
They've all learned we are not be feared. We are a potential meal.
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