Sexual selection is natural selection due to variation in mating success. Sexual selection acting through female choice of mates has been extremely important in shaping the evolution of animal communication. Females of many species show preferences based on male signal characteristics such as the rate or complexity of vocal signals or the wavelength of visual signals. A number of theories have been proposed to explain the evolution of such preferences, including ones in which preferences benefit females directly, by enhancing their survival or reproduction, and ones in which preferences benefit females indirectly, through the increased fitness of their offspring. © 2009 Elsevier Ltd All rights reserved.