The influence of water velocity on the display behavior of male guppies, Poecilia reticulata

The objective of this experiment was to determine if different water velocities during ontogeny affect male physical condition, male signal intensity, and female mating preferences in the guppy (Poecilia reticulata). Guppies were raised in aquaria in either high or low water velocities and fed in excess. Analysis of 72 males from four replicates indicated that high velocity males had longer mean displays and spent more total time displaying than low velocity males. These males also had significandy faster swimming speeds, wider caudal peduncles, and were more attractive to females than low velocity males. There were no differ-ences in display rates, body widths, standard lengths, or copulation attempts between high and low velocity males. These results indicate that water velocity conditions during ontogeny act as a proximal factor diat influences the display behavior of guppies. Water velocity caused an indirect increase in the power of the male display to produce a female sexual response. The morpho-metric measurements suggest that die proximal mechanism behind the increased display intensity was the increased muscle development of males raised in high water velocities, which resulted in longer prolonged swimming speeds and more intense displays. Therefore, display behavior of guppies may be a general indicator of overall male physical condition. Key words: display behavior, guppy, Poecilia reticulata, water velocity. [Behav Ecol 7:272-278 (1996)] Many male secondary sexual characteristics and behaviorsare thought to have evolved by sexual selection by fe-male choice (Andersson and Bradbury, 1987). Many of these characteristics apparently function as signals during mate choice. Examples of sexually selected signals are the nuptial coloration and display behavior of some fishes (Bakker an