Mating signals are diverse and often spectacular. Signalers often pay a large cost in terms of energy and increased predation risks in order to attract a mate, which may assess several different aspects of the signals before committing to any individual. Highly invariant properties often convey species or individual identification, whereas variable, dynamic properties are often honest indicators of a signaler’s physical or genetic fitness. The use of a particular signaling modality and different values of the properties of signals are also influenced by the environment and the time of day. Usually, such design features increase the range of detection of a signal by a prospective mate. Chemical and acoustic signals work well night and day and in dense habitats, but the delivery of a chemical signal is much slower and usually much more uncertain. Visual signals are immediately located in well-lit environments with a clear line-of-sight. Rapid exchanges involving signal production by both sexes are possible with visual and acoustic signals, and the timing of these exchanges can itself provide information about the signaler’s identity. Many species combine signals of different modalities and sometimes switch to less conspicuous signals after the detection of a potential mate, thus reducing the chances of attracting a rival or a predator.