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Microhabitat Choice in Island Lizards Enhances Camouflage Against Avian Predators

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Microhabitat Choice in Island Lizards Enhances Camouflage Against Avian Predators

Kate L A Marshall et al. Sci Rep.

Abstract

Camouflage can often be enhanced by genetic adaptation to different local environments. However, it is less clear how individual behaviour improves camouflage effectiveness. We investigated whether individual Aegean wall lizards (Podarcis erhardii) inhabiting different islands rest on backgrounds that improve camouflage against avian predators. In free-ranging lizards, we found that dorsal regions were better matched against chosen backgrounds than against other backgrounds on the same island. This suggests that P. erhardii make background choices that heighten individual-specific concealment. In achromatic camouflage, this effect was more evident in females and was less distinct in an island population with lower predation risk. This suggests that behavioural enhancement of camouflage may be more important in females than in sexually competing males and related to predation risk. However, in an arena experiment, lizards did not choose the background that improved camouflage, most likely due to the artificial conditions. Overall, our results provide evidence that behavioural preferences for substrates can enhance individual camouflage of lizards in natural microhabitats, and that such adaptations may be sexually dimorphic and dependent on local environments. This research emphasizes the importance of considering links between ecology, behaviour, and appearance in studies of intraspecific colour variation and local adaptation.

Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Representative drawing of the arena experiment set-up.
Two differently coloured rocks (rock A and rock B) were placed side-by-side in the centre of the enclosure. Video cameras recorded background choices made by each lizard while experimenters were out of sight. In subsequent video analysis, if the lizard showed better camouflage against one rock than the other rock as perceived by avian predators (JND) then it was expected to spend a greater proportion of time on that rock. This would indicate a background choice to enhance individual camouflage.
Figure 2
Figure 2. Background-matching camouflage in free-ranging lizards.
This shows the degree of chromatic (left axis; black data points) and luminance (right axis; red data points) background matching (mean JND ± 1.00 S.E) of the dorsal regions of free-ranging Aegean wall lizards (Podarcis erhardii). Dorsal matching against ‘own’ chosen backgrounds (rock substrates the lizards were observed resting on) and against other lizards’ backgrounds (other) on the same island is shown in four island populations (Folegandros, Santorini, Skopelos and Syros) and in males and females (N = 263; Folegandros = 100; Syros = 49; Santorini = 58; and Skopelos = 56 [149 males, 114 females]). Generally, values ≤3.00 JND depict lizards that are indistinguishable (camouflaged) against the background to avian predators under natural lighting conditions,, while values increasing >3.00 JND depict lizards that are increasingly distinguishable.
Figure 3
Figure 3. Arena experiment: Differences in preference strength between trials with “benefit” and “no benefit” to camouflage (N = 58).
The largest proportion of time Aegean wall lizards (Podarcis erhardii) spent on one of two backgrounds (out of the total time spent on both) indicated the strength of the preference for that background. Trials provided a camouflage “benefit” when individuals were indistinguishable against one background to avian predators (i.e., ≤3.00 JND). Other trials provided “no benefit” to camouflage because lizards were distinguishable against both backgrounds to avian predators (i.e., >3.00 JND).

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