Predation, light intensity and courtship behaviour in Poecilia reticulata (Pisces: Poeciliidae)

The colour patterns of guppies, Poecilia reticulata, represent a balance between selection for crypsis (by predators) and selection for conspicuousness (by females). To a predator or mate, the conspicuousness of a colour pattern depends on environmental light conditions at the time of viewing. In this study light intensity and predation had significant effects on male courtship behaviour in guppies. Males courted less and used visually conspicuous behavioural elements less often in the presence of predators or under high light levels. Maximum risk due to predation naturally occurs at the highest light intensities, so either light intensity or the presence of a predator can be used as a cue for predator avoidance. Guppies minimized predator risk during courtship by shifting visually conspicuous displays to times of day when visual predation is minimal, and using the visually less conspicuous sneak copulation strategy when predation risk is greatest. Because ambient light conditions vary with time of day, the same colour patterns are seen under different visual conditions by predators and mates. Such context-dependent conspicuousness reduces the need for an evolutionary compromise between colour patterns that reduce the risk of visual predation and those that increase visibility to females. © 1987.