Wall lizards display conspicuous signals to conspecifics and reduce detection by avian predators

Abstract

Visual signals are often under conflicting selection to be hidden from predators while being conspicuous to mates and rivals. Here, we investigated whether 3 different island populations of Aegean wall lizards (Podarcis erhardii) with variable coloration among diverse island habitats exhibit simultaneous camouflage and sexual signals. We examined whether signals appear better tuned to conspecific vision as opposed to that of avian predators, and whether background-matching camouflage and sexual signals are partitioned to specific body regions. This could facilitate both covert sexual signaling and camouflage according to the viewing perspectives of predators and conspecifics. We found that lizards typically appeared twice as conspicuous to conspecifics than to avian predators against the same visual background, largely due to lizards’ enhanced sensitivity to ultraviolet, suggesting that P. erhardii signals are tuned to conspecific vision to reduce detection by predators. Males were more conspicuous than females to both predators and conspecifics. In 2 populations, male backs were relatively more camouflaged to predators compared to signaling flanks, whereas in females, exposed and concealed surfaces were camouflaged to predators and generally did not differ in background matching. These findings indicate that lizard coloration evolves under the competing demands of natural and sexual selection to promote signals that are visible to conspecifics while being less perceptible to avian predators. They also elucidate how interactions between natural and sexual selection influence signal detectability and partitioning to different body regions, highlighting the importance of considering receiver vision, viewing perspectives, and signaling environments in studies of signal evolution.

Conspicuous male coloration impairs survival against avian predators in Aegean wall lizards, Podarcis erhardii

“…As shown in previous work (Marshall and Stevens ), our findings support the idea that selection has favored more camouflaged coloration in female P. erhardii , resulting in their relatively high survival (i.e., low attack rate) against avian predators. In contrast, conspicuousness appears to be more important in males, possibly for intra‐ and intersexual signaling, particularly as male lizards are known to exhibit conspicuous colors to attract mates and deter rival males, even on more exposed dorsal regions in P. erhardii (see Fig.…”

“…This imitated where real lizards usually bask and where they are potentially visible to avian predators (e.g., Bauwens et al. ) and was comparable to previous measurements of P. erhardii camouflage against rock backgrounds (Marshall and Stevens ; Marshall et al., in press).…”

“…We recorded photographed lizards' locations using a Garmin eTrex ® GPS device (Schauffhausen, Switzerland) and marked them with colored tape to indicate sex and lifestage estimated using a field guide (Arnold and Ovenden ). We confirmed these estimations were 99% reliable by comparing estimated (from photographs) and observed sex and lifestages from captured lizards (see Marshall and Stevens ). We avoided pseudoreplication by never repeating photography of a lizard of the same sex within the same home range (i.e., within 10 m) (Verwaijen and Van Damme ).…”

“…; Pérez i de Lanuza et al. ; Marshall and Stevens ). However, conspicuous signals in males may increase the risk of detection and attack by predators (e.g,.…”

“…; Rosenblum ; Rosenblum et al. ; Marshall and Stevens ; McLean et al. ; but see for example Vignieri et al.…”