alternative behaviours are maintained through frequency-dependent selection because of their equal fitness benefits and functional equivalence. under frequency-dependent selection, the fitness of a given phenotype is determined by its frequency relative to other phenotypes within a population. similarly, negative frequency-dependent selection describes a scenario in which rarer phenotypes experience greater fitness. given that the utilization of alternative mating strategies has been shown to fluctuate over time, it has been suggested that frequency or negative frequency-dependent selection is the mechanism through which alternative mating strategies are maintained in animal populations.