The use of digitally-modified videos to study the function of ornamentation and courtship in the guppy, Poecilia reticulata

The use of video playback, digitally-modified video images, and animations is a potentially powerful tool for exploring the interactions between morph ological and behavioral components of complex sexually selected traits. The utility of digitally-modified video was evaluated by the responses of fema les to male images in which either the behavioral components of display or the colors of ornamentation were manipulated. Females were presented with p aired male images that varied only in the size of the orange or blue spot o n the body (19.1% vs. 8.6%), courtship duration (7 sec vs. 2.3 sec), or cou rtship rate (3 displays min(-1) vs. 1 display min(-1)). Females preferred m ale images with more vigorous courtship displays (both duration and rate) b ut did not discriminate between images differing in spot size. The results of the present study suggest that females discriminate more strongly betwee n variation in male behavior than in their morphological attributes. The re sults of morphological manipulations should be interpreted with caution, ho wever, because several factors could have contributed to the lack of female responses to color spot variation. Among them are lowered resolution of th e computer image, which fails to capture the precision and complexity of th e color pattern. Despite these potential difficulties, digitally-modified v ideo promises to be a powerful method to study complex visual communication systems, where the function of and interaction between the various morphol ogical and behavioral components is as yet poorly understood.