Throat UV reflectance plays the role of a conventional badge of status during male-male interactions in the common lizard
Ultraviolet (UV) body colourations are widespread in vertebrates. In many species, males display strong among-individual variation and are usually brighter than females suggesting a possible intraspecific signalling function. However, our knowledge of functions of UV colourations as well as conveyed information and cost associated with production of such ornaments remains unclear and limited. We studied these issues in the common lizard Zootoca vivipara that exhibits a UV/carotenoid-based ventral colouration. UV colour is particularly expressed on the males’ throat that is exposed to the opponents’ sight during behavioural displays. We first carried out an analysis of retinal physiology in order to determine whether common lizards possess retinal specialization and spectral sensitivity required to UV perception. Second, to assess if the trait is costly to produce and thus honestly reflects the quality of the bearers, we led a correlative study between throat UV saturation and some indicators of the individual’s health state (T-cell mediated response, parasites load, testosterone level, and body condition). Third, we experimentally investigated whether UV colours influence male conflict resolution by manipulating the signal with a UV-reducing cream. Controlling for body size, mass and carotenoid ventral colouration, we staged repeated encounters between resident and intruder males in which UV reflectance was alternatively or simultaneously reduced in a full factorial design and quantified precisely behaviours. Our results confirmed that the retina of Zootoca vivipara contains UV-sensitive photoreceptors and highlighted no correlation between the throat UV saturation and the health indicators. We also found that the UV manipulation affected aggressive behaviours as well as contest outcomes of male pairs. Overall, these results suggest that common lizards are capable to perceive their conspecifics’ UV colouration that appears to not be costly to produce and acts as a badge of status involved in the assessment process of the fighting ability of opponents.
Martin M., Meylan S. and Le Galliard J.F. Throat UV reflectance plays the role of a conventional badge of status during male-male interactions in a lizard. Ecology & Behaviour 2014. Montpellier, France. Talk.