Signalling Theory - Dishonest Signals

Dishonest Signals

Because there are both mutual and conflicting interests in most animal signalling systems, the fundamental problem in evolutionary signalling games is dishonesty or cheating. Why don’t foraging birds just give warning calls all the time, at random (false alarms), just in case a predator is nearby? If peacocks with bigger tails are preferred by peahens, why don’t all peacocks display big tails? Too much cheating would disrupt the correlation at the foundation of the system, causing it to collapse. Receivers should ignore the signals if they are not useful to them and signallers shouldn’t invest in costly signals if they won’t alter the behavior of receivers in ways that benefit the signaller. What prevents cheating from destabilizing signalling systems? It might be apparent that the costs of displaying signals must be an important part of the answer. However, understanding how costs can stabilize an "honest" correlation between the public signal trait and the private signalled quality has turned out to be a long, interesting process. If many animals in a group send too many dishonest signals, then their entire signalling system will collapse, leading to much poorer fitness of the group as a whole. Every dishonest signal weakens the integrity of the signalling system, and thus weakens the fitness of the group.

An example of dishonest signalling comes from Fiddler crabs such as Uca lactea mjoebergi, which have been shown to bluff in regards to their fighting ability. Upon regrowing a lost claw, a crab will occasionally regrow a weaker claw that nevertheless intimidates crabs with smaller but stronger claws. The proportion of dishonest signals is low enough that it is not worthwhile for crabs to test the honesty of such signals, as combat can be dangerous and expensive.