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Animal communication that is primarily innate includes signaling based on fixed action patterns. Fixed action patterns are genetically encoded and occur spontaneously when the animal is presented with an environmental cue, or sign stimulus, which acts as a trigger. Researchers have observed a vivid example of this behavior in the male stickleback fish, who flaunts his flame-red belly in fighting postures when another male invades his territory at mating time. A male stickleback will produce the same postures when confronted with models of fish showing bright red undersides. These postures are fixed action patterns because the red coloring-the sign stimulus-provokes identical behavior in all male sticklebacks. In contrast, communication as learned behavior is clearly demonstrated in birds, whose songs are often influenced by other birds. The white-crowned sparrow, for example, has a rudimentary song coded in its genes but modifies the song to match that of other white-crowned sparrows living nearby. Researchers have found that young white-crowned sparrows living in isolation the first few months of their lives never develop their songs past the rudimentary version. This critical period-the time where early learning must take place-is a common feature of learned behavior in animals.

Visual displays include a rich array of facial expressions, body movements, coloration, and physical shapes, such as the male peacock's fanned tail. Visual communication is easy to produce, instantaneous, and can be modified to carry various types of information. For example, a dog may raise its hackles in warning when a potential enemy approaches and then lower them if the approaching animal or human appears friendly. Visual displays can be momentary, such as raised hackles; cyclical, such as the reddened rump of a female chimpanzee that signals readiness for mating; or permanent, as evident in the scarlet and purple facial markings of a male mandrill that enhance his facial expressions. They can be as simple as a male stickleback's reddened belly, or as complex as a mountain gorilla's dominance ritual, which includes rising to a standing position, chest-slapping, tipping the head to one side, and tearing up and tossing vegetation. Different aspects of an animal's body may be used in visual display, depending on both individual anatomy and environment. Most reptiles, for instance, have body parts that inflate to show aggression. Animals living on land, including humans and other primates, rely primarily on the head and face for producing visual displays. Fish, in contrast, use their gills and fins. Some structures used for visual display serve additional functions as well.