Communication and Signals - An Introduction to Behavioural Ecology - page 422

(1) Indices are signals that cannot be faked. Examples include the croaks of toads, and
the roars of deer.
(2) Handicaps are signals that could be faked, but where doing so is not economically
beneficial. One possibility is that signals are costly to produce and the cost is greater for
poor quality individuals. Examples include many of the extravagant sexual ornaments
discussed in Chapter 7, such as the eye span in stalk-eyed flies, and how offspring beg
for food from their parents, as discussed in Chapter 8. Another possibility is that
dishonest signals incur social costs such as punishment. Examples include badges of
status such as the black bib of sparrows or the facial markings of hover wasps.
(3) The sender and receiver can have a common interest in the interpretation of the
signal. Examples include the waggle dance of the honeybee, quorum sensing in
bacteria, receptivity in fruit flies and the chirrup calls of sparrows.
Language is a crucial difference between humans and other animals. Honesty in
human language could be explained by a common interest and/or the social cost of
dishonesty.
Dishonest signalling will only be evolutionarily stable if, on average, it pays the receiver
to respond to the signal. Examples include the lures of anglerfish, Batesian mimicry, the
false alarm calls of fork-tailed drongos and soft weapon displays in mantis shrimp.
Further reading
The evolution of communication and signals has been reviewed in three excellent topics
(Maynard Smith & Harper, 2003; Searcy & Nowicki, 2005; Bradbury & Vehrencamp,
2011). The differences between these topics illustrate how the overarching conceptual
framework, in terms of how the different explanations for signalling are carved up, is
still a matter of debate.
Nakagawa et al . (2007) show how meta-analysis can be used to assess whether bib
size acts as a badge of status in the house sparrow, Passer domesticus . Cotton et al .
(2004b) review evidence that condition dependent expression (as required by handicaps)
occurs and find the data lacking. Scott-Phillips & Kirby (2010) review laboratory
experiments on the evolution of human language.
Keller and Surette (2006) provide an excellent discussion of signalling in bacteria
from a behavioural ecology perspective. Kohler et al . (2009) and Rumbaugh et al . (2009)
demonstrate the importance of quorum sensing for the damage that parasites do their
hosts (virulence) and discuss how signalling theory can illuminate clinical patterns.
Jackson et al . (2004) provide a fascinating example of how ants supply information
about trail direction through the use of geometry. Tobias and Seddon (2009) show how
environmental condition can move a signal from common interest to conflict, with
duetting and jamming in a pair-living antbird ( Hypocnemis peruviana ). Radford et al .
(2011) show that the interaction between drongos and babblers may sometimes be
mutually beneficial, despite kleptoparasitism, because the babblers get a net benefit
from drongo vigilance.