Control, suppression, decay, disappearance and replacement of displays.

Abstract Published descriptions by various authors indicate that many species of mammals, birds, and fish have similar numbers of major displays (ritualized social signals) despite great differences in habitus and social structure. The usual range of adult displays would seem to be from approximately 15 to approximately 35. It is surprising that the range is so narrow. The crucial question is why numbers have not increased more. The answer may lie in some effects of diversity. Any increase in the number of displays will entail greater diversity in their forms. It may also mean that some of them can be given only rarely. Rare displays of peculiar form may be unexpected (by their receivers) in circumstances in which surprise would be disadvantageous. The relative stability of numbers is a dynamic equilibrium. There has been loss of old displays as well as gain of new ones during evolution. The immediate causes of the decline of particular displays must be extremely varied, but one would expect such patterns to become progressively more vulnerable or susceptible to decay with age. They will usually tend to become more “attenuated”, less meaningful, and/or more exaggerated in form as time passes. Displays can be lost by becoming increasingly rare, fusing with other patterns, or by a process of “de-ritualization”. Many potential replacement patterns must be available whenever a display starts to decay. There will probably be competition among signals as well as among individuals. A display may be replaced by another pattern of almost any origin but probably not any form. The replacements should be neither too similar to, nor too different from, the patterns being replaced.