The role of social costs as a mechanism enforcing the honesty of ultraviolet-reflecting signals in a lizard

Abstract

According to animal signalling theory, social costs incurred by aggressive conspecifics are one mechanism maintaining signal honesty. Although our understanding of signal evolution has much improved for pigment-based colours, the mechanisms maintaining the honesty of structural colour signals, such as ultraviolet (UV), remain elusive. Here, we used the common lizard (Zootoca vivipara) to test whether the honesty of UV-reflecting signals displayed on male throats is under social control. To do so, we staged agonistic interactions between non-manipulated focal males and opponents of either larger or smaller body size. We manipulated the UV component of the male throat colour patch to create small cheaters with UV-enhanced throats, large cheaters with UV-reduced throats, and their respective controls. In support of a conventional signal hypothesis, focal males were aggressive towards large cheaters and became submissive when these large cheaters retaliated, and were less submissive against small cheaters. However, that focal males were not more aggressive towards small cheaters contradicts our initial predictions. We confirm that male UV reflectance and bite force were good predictors of contest outcomes in control conditions. Overall, we provide partial evidence suggesting that social costs enforce UV signal honesty in common lizards.

Environmental conditions and male quality traits simultaneously explain variation of multiple colour signals in male lizards

“…Furthermore, the throat UV colouration of males correlated (albeit weakly based on values of the coefficient of determination) with maximal sprint speed, a trait important for fitness in lizards (Miles, 2004). This result is consistent with the role of UV signals previously identified in this species during male-male competition (Martin et al, 2016;Kawamoto et al, 2021) and female mate choice . Our study thus indicates that receivers can extract information about multiple aspects of male condition including locomotor performance, bite force and parasite infestation from several components of the colouration of adult male common lizards.…”

“…Male common lizards have a conspicuous, carotenoid‐based ventral colouration that ranges from yellow to orange, with a varying amount of melanic black spots dispersed along the venter, and a conspicuous UV‐white throat (Bonnaffé et al, 2018; Figure 1). The UV colouration on the throat plays a role during male–male competition (Martin et al, 2016) and female mate choice (Badiane et al, 2020), and is associated with social costs during male–male interactions (Kawamoto et al, 2021). Similarly, the amount of black ventral colouration correlates positively with male bite force, but decreases with sprint speed (San‐Jose et al, 2017).…”

“…However, the costs associated with pterin-based and structural colour signals, if any, remain largely unknown (Andrade & Carneiro, 2021;Kemp et al, 2012), although social costs are potential candidates (e.g. Kawamoto et al, 2021). If we are to comprehend how colour signals become evolutionarily stable, it is critical to understand how the relationships between a colour signal, its information content and environmental factors vary based on the different production modes of multiple colour signals.…”

Behavioural response to predation risks depends on experimental change in dehydration state in a lizard

“…The presence of predator scents increased activity rate but in the meantime it decreased basking rate during activity. Increased activity can be associated with a higher level of vigilance and also more frequent escape attempts (via scratching behaviours, see Kawamoto, Le Galliard & Badiane, 2021), but this was not correlated with a better thermoregulation. On the contrary, lizards spent less time basking, which is consistent with the observed reduction of mean active body temperature in presence of predation threat.…”

Active regulation of ultraviolet light exposure overrides thermal preference behaviour in eastern fence lizards

“…Sceloporus sp., Eakin & Westfall, 1960; Stebbins, 1963; Stebbins & Eakin, 1958). Lizard social systems also take advantage of these UV detection capabilities for intraspecific communication (Kawamoto et al, 2021; Stoehr & McGraw, 2001; Whiting et al, 2006). Focusing on individual physiology, UV exposure stimulates endogenous production of vitamin D 3 (Holick et al, 1995).…”