I usually leave things as they are. I like to remain as distant from the scene as possible to capture the events as they would without my presence. Admittedly though, sometimes I have manipulated nature in order to get my desired shot. Specifically with snakes. Generally, snakes will move away from you when your around. The only way Ive known to battle this is to control the snake itself, while in its environment. The snake will normally sit still and keep an eye on me, leaving me enough time to take several shots before he moves, and then Ill grab it and move it again. I do not intentionally feed animals to draw them in or go to the zoo to take images either. Anything wildlife photography I capture is always as I see it in the wild(with the exception of snakes). As much as I would like to feed birds to draw them near also nears the ethics borderline as well. I prefer to catch animals in their native habitat, not next to a feeder, or behind a piece of glass. Im not saying I make ethical decisions 100% of the time, but that is generally the case.