Hi, It depends on which animals you're talking about. Humans are large mammals, and we tend to compete for environmental resources most directly with other large mammals. On the other hand, we have enormous impacts on ecosystems on a global scale, mainly because there's just so damn many of us. To take a random example, there are currently about 750,000 elephants in existence, as an upper estimate. But there are 7 billion human beings: that's 7,000,000,000. So, for every elephant on the planet there are roughly 1000 human beings. As a species, humanity's big advantage over other mammals is our large brains, and tool use - technology. The current level of technology we have has developed in an evolutionary blink of an eye, which has meant that we have out-competed every other major predator on the planet in only the last 10,000 years or so. Restricted to "natural" defences, other animals are limited in what they can hope to achieve in encounters with human beings, especially in numbers. The best thing they can do, in general, is to hide or run away when they see humans coming - and most of them do exactly that. Moving away from large mammals, many species that do not share such close evolutionary niches with human beings have, until relatively recently, managed to co-exist with human beings without much conflict. However, non-domesticated species that we used for food are all suffering; witness the over-fishing of the oceans, to take one example. Many species are also "collateral damage" of human expansionism and activity. We cut down forests. We spoil otherwise pristine environments all over the world. We dump our waste on land and into the oceans. In the process, many species have been made extinct or brought to the edge of extinction. Now, of course, we are conducting an uncontrolled experiment in global climate engineering, which is already having negative impacts not only on other species but also on millions of human beings. And it will only get worse unless we get serious about doing something to mitigate the harm we are causing. Some species, of course, actually benefit from being around human beings. There are far more cats and dogs in the world than there would be without so many human beings. There are lots of microorganisms that thrive on human bodies and on human products. Having a bullet-resistant hide doesn't come without cost. Maintaining a thick hide means the animals probably needs to eat more food. It might also restrict its freedom of movement. Everything in evolutionary "fitness" is a tradeoff. An adaptation only makes evolutionary sense if, in context, it gives a net survival advantage. It could well be that if you're a tiger, it would be evolutionarily more advantageous to simply hide from human beings in the rainforest rather than growing a bullet-proof hide.