Re: Why do animals try to bluff their way out of fights?

If you think about two animals fighting, you can easily imagine that they would be able to hurt each other. Well, neither of them wants to be hurt, right? (OK, maybe I'm being anthropomorphic [attributing human emotions and intentions to animals] by saying "wants," but think of it as a shorthand; what I really mean is, it is not in the evolutionary best interest of either animal to be hurt, because injury might prevent it from surviving or breeding in the future.) It's a lot easier for both animals to perform displays (mallard ducks flash a particularly bright patch of feathers, red deer "roar") at one another, or, as you say, bluff their way out of the fight. That way neither is injured and the dispute is settled based on the displays (who had the brighter patch of feathers, or was more persistent in flashing the feathers, who roared louder or longer).

I'm not sure if you used the word "bluff" intentionally--did you mean to imply that one or both animals were trying to deceive the other into giving up on the fight? Actually, a lot of scientists are doing research on this area of communication and deception. Some displays used by animals are "honest": they give some kind of realistic description of the strength or size of the animal (for instance, roaring in red deer takes a lot of energy, so whichever male can do it longer is the stronger male and would probably win a fight, if it came to that). But some displays are probably deceptive: if the animal performing the display does not need more energy or more strength or whatever to make a more impressive display, then the animal can do so and "lie." Then it's up to the other animal to figure out whether the first one is lying, and whether or not it is worthwhile to fight.