Trade-off between camouflage and sexual dimorphism revealed by UV digital imaging: the case of Australian Mallee dragons (Ctenophorus fordi).

Colour patterns displayed by animals may result from the balance of the opposing requirements of sexual selection through display and natural selection through camouflage. Currently, little is known about the possibility of the dual purpose of an animal colour pattern in the UV region of the spectrum, which is potentially perceivable by both predators and conspecifics for detection or communication purposes. Here, we implemented linearised digital UV photography to characterise and quantify the colour pattern of an endemic Australian Agamid lizard classically regarded as monomorphic when considering data from the visible region of the spectrum. Our results indicate a widespread presence of UV elements across the entire body of the lizards and these patterns vary significantly in intensity, size and frequency between sexes. These results were modelled considering either lizard or avian visual characteristics, revealing that UV reflectance represents a trade-off between the requirements of sexual displaying to conspecifics and concealment from avian predators.