A picture is worth a thousand dollars: a photographic approach to studying colour in anoles

Colours relay information to conspecifics and predators unique to an environment and are shaped by natural selection favouring colours that enable higher fitness. For decades, ecologists have grappled with various methods of quantifying colour. Spectrophotometers offer precise and accurate data, but their high price limits accessibility. Here we test the validity of an accessible method of quantifying colour. We analysed photographs from four species of Anolis lizards from urban and forest habitats. We compared dewlap colour in order to determine if photographic analysis can detect inter- and intraspecific differences with the same power as a spectrophotometer. We hypothesized that photographs would capture colour data comparable to a spectrophotometer within the visible light range, and that habitat divergence would be associated with intraspecific differences in dewlap. We demonstrate, as hypothesized, that photographic colour data are consistent with spectrophotometer data and capable of differentiating dewlap variation within the visible light spectrum. Differences in colour between urban and forest populations were significant for some but not all species, and the part of the colour spectrum that shifted was not consistent across species. Our results support photographic analysis as an alternative for quantifying colour to study both inter- and intraspecific variation in visible colour.