Most behaviors do not occur in isolation, but rather are the result of
interactions between members of a species or between members of different
species. The topics of signaling and communication include behaviors from simple
scent marking to complex courtship displays that involve multiple individuals.
The distinction between signaling and communication is not entirely clear.
Generally, signaling involves a stimulus that is not intended by the individual
to send a message to a receiver, while communication is a deliberate act in
which the exchange of information is mutually beneficial.
Some signals begin as behaviors with entirely different purposes but become
exaggerated or ritualized as they become recognized for conferring
information in a beneficial way. These signals are then acted on by natural
selection to minimize risk to the signaler. A danger signal will become very
exaggerated whereas cooperative signals will be minimized to reduce the
conspicuousness of the signaler. Zahavi's handicap principle states that an
honest signal must be costly to the signaler, meaning that only fit individuals
can signal honestly. This principle is especially important in activities such
as mate selection, in which finding a truly fit individual is extremely
important. There are many types of signals, each with its own advantages and
disadvantages. Among these are: chemical signaling, such as scent marking;
visual signaling, which while limited to individuals in a direct line of site
can be much more dynamic than other types of signaling; and acoustic signals,
which are often among the most wide-reaching signals. Acoustic signals such as
bird and whale songs have both genetically pre-determined and learned components
and can be used to distinguish individuals or living groups.