Deceit versus honest signalling

Natural selection should favor any signal that enhances an animal's likelihood of reproduction. Honest signals in communication are given when both the sender and receiver have the same interest in the result. Deceit comes about when one animal can exploit another in order to improve its fitness.

The most obvious arena for deceit is mate choice. Natural selection strongly favors any device which increases an animal's reproduction; if a dishonest or deceitful signal does that, then genes for the signal will spread rapidly in a population. Another context is parental care, in which young may use signals which exagerate their actual needs in order to extract more than minimal care from a parent. Given the apparent advantages of deceptive behavior, studies which show deceit within a species, other than extrapair-copulations (EPC's), are surprisingly rare. This rarity may be due to the fact that the receiver has the upper hand in choosing whether or not to respond to a signal, and consequently can enforce honesty.

Scientists have only recently recognized the high frequency of extra-pair copulatons by female aimals in seemingly monogamous species of birds and mammals. These often result in extra-pair paternity (EPP) of offspring. In species which have apparently monogamous mating systems, so that a male and female are pair-bonded, females may seek copulations with other males, doing so at times or locations which make detection by their pair-bonded male unlikely. This phenomenon is best studied in apparently monogamous birds; averaged over a large number of species, 13% of the offspring were sired by non-pair males. Behavioral deception (secretively copulating) plays an in important role in facilitating this behavior.

Honest signalling in mate choice and parental care arises when production of the signal is costly to the sender (the handicap principle) (Zahavi 1975, 1977). If the receiver responds only to costly signals, the communication evolves to reflect the sender's ability to pay the cost.

When a mate attraction signal is costly to produce, as are cricket chirps or frog calls, males which are unable to produce attractive, yet costly, signals sometimes adopt a satellite strategy. Satellite males lurk near calling males, intercept females approaching the attractive male, and attempt, sometimes successfully, to mate. This type of deceit takes advantage of a calling males inability to guard females as they approach.

Deceit is common in signals which function between species, as well. Generally these are modifications or adaptations of signals used in intraspecific communication in order to exploit that species. Carnivorous fireflies mimic the mate attraction signals (light flashes) of other species, attracting males looking for would-be mates; the encounter ends in death instead (Lloyd 1975). Bolas spiders use moth sex pheromones in a similar manner (Eberhard 1977). "Guests" in ant nests acquire the chemical signature used by the ants to discriminate nest members from non-members (Vandermeer and Wojcik 1982). Signals such as these are aggressive mimicry, which take advantage of the victim's need to communicate.

Dawkins M. S., Guilford T. 1991 The corruption of honest signaling. Animal Behaviour 41: 865-873

Eberhard, W. G. 1977. Aggressive chemical mimicry by a bolas spider. Science 198: (4322) 1173-1175

Enquist, M. 1985 Communication during aggressive interactions with particular reference to variation in choice of behavior. Animal Behaviour 33: 1152-1161

Lloyd, J. E. 1975. Aggressive mimicry in Photuris fireflies: Signal repertoires by femmes fetales. Science 197:452-453.

Smith, J. M. 1991 Honest signaling - the Philip Sidney game. Animal Behaviour 42: 1034-1035

Stowe M. K., Turlings T. C. J., Loughrin J. H., Lewis W. J., Tumlinson J. H. 1995. The chemistry of eavesdropping, alarm, and deceit. Proceedings of the National Academy of Sciences of the United States of America 92: (1) 23 28

Vandermeer, R. K., Wojcik, D. P. 1982. Chemical mimicry in the myrmecophilous beetle Myrmecaphodius excavaticollis. Science 218: (4574) 806-808

Zahavi, A, 1975. Mate selection - selection for a handicap. J Theor Biol 53: (1) 205-214

Zahavi, A. 1977 Cost of honesty - (further remarks on handicap principle). Journal Of Theoretical Biology 67: (3) 603-605