The Use of A Feeding Assay to Test the Effects of Visual Color Contrast on Stimulus Visibility in the Lizard Anolis sagrei and the Evolution of Anolis species in the Dominican Republic

Many animals depend on color signals for communication. It has been hypothesized that signals evolve toward maximum visibility against natural backgrounds. Testing this hypothesis requires a way to assess the influence of signal/background color contrast on signal visibility. Most tests such as these rely on training, which can be very time consuming and difficult for some types of animals. We created a method for testing color contrasts using the lizard Anolis sagrei. We colored dead worms using powdered food coloring and placed them on backgrounds of varying colors and luminance. We presented stimuli in pairs that differed in contrast with the background, and determined that most individuals would choose the more visible food item first. We examined the effects of luminance and color contrast on stimulus visibility, and also tested for any inherent bias in preference for specific colors. Finally, we tested the effects of low light conditions on spectral contrast based visibility. We expected low light to reduce the effects of spectral contrast because it is known to elevate color discrimination thresholds. We found that this method is an effective approach to testing signal visibility in an animal that is difficult to study with standard conditioning techniques. We also wanted to see if dewlaps evolved towards maximum visibility in Anolis species in the Dominican Republic. We collected light habitat data, dewlap color data, and body color data on five different species of anoles in the Dominican Republic and compared the data using a tetrahedral perceptual color space program. We found that not only did the background play a role in the evolution of the dewlap color, but also species discrimination was a driving evolutionary factor in Anolis species of the Dominican Republic