Seeing red: pteridine-based colour and male quality in a dragon lizard

The animal kingdom is represented by a spectacular diversity of colourful species. However, for particular groups, such as lizards, we still know little about the nature of these colours and what they might signal about individual quality. In eastern water dragons (Intellagama lesueurii), males are larger than females and have a red venter. We first identified the pigments responsible for the red coloration. We then used visual modelling to determine how conspicuous red colouration is to a dragon lizard. Finally, we asked whether colour signalled male morphology and whether parasitized males had reduced coloration. The red coloration of male water dragons is produced by both carotenoid and pteridine classes of pigments, but predominantly by drosopterin, a coloured pteridine. Heavy males with large heads and in good body condition and those with fewer ticks had less intense red coloration on the chest, abdomen and thighs. However, size was not correlated with any colour variables. We explain the negative relationship between colour conspicuousness and morphological variables by the fact that less conspicuous males might have more melanin interspersed with red. Future studies are needed to investigate the interplay between pteridines and melanin in social signals of male quality in dragon lizards.