Manipulated (n=54) and control (n=54) lizards did not significantly differ in SVL (t=−0.72, p=0.47) or head size (head width: t=0.50, p=0.60; head length: t=1.61, p=0.11; head depth: t=1.03, p=0.30). Prior to manipulation, UV-chroma and hue did not vary between control and manipulated males (UV-chroma: t=−1.4, p=0.15; hue: t=−0.12, p=0.89). The application, however, was effective at reducing throat UV of males in the manipulated group via a decrease in UV-chroma and an increase in hue (, ).
Mean reflectance spectra of male throats. (a) Control group and (b) manipulated group before (solid line) and after (dashed line) application of sunblock–car wax combination.
In total, 62 males (32 control: 16 floaters, 16 territorial; 30 manipulated: 11 floaters, 19 territorial) were observed in 259 contests in the 2 days following manipulation. Initiators were more likely to win (163
59) and territorial males were more likely to initiate contests (initiator ART: F1,119
<0.001). Contest escalation and/or duration was not influenced by whether the receiver had his throat UV manipulated (escalate F1,190
=0.98, duration F1,190
=0.45). However, the probability of a contest escalating was greater when the initiator's throat UV was reduced (a
=0.02). The log duration of contests was related to the escalation and the interaction between escalation and manipulation, but not related to other factors such as territoriality (escalation: F1,190
<0.001; treatment: F1,190
=0.13; treatment×escalation: F1,190
=0.02). Ventral displays were longer for manipulated males but duration of escalated contest did not vary with manipulation (b
). Contest outcome was not influenced by manipulation. There was, however, a weak trend (p
<0.1) for territorial males to win contests and a strong influence of receiver ART on contest outcome (initiator ART: F1,30
=0.08, power for a small effect size (0.15)=0.83; receiver ART: F1,62
<0.001). As such the initiator was less likely to win if the receiver was territorial (22%) compared to if the receiver was a floater (78%).
(a) Proportion of non-escalated (open) and escalated (shaded) contests and (b) mean log duration (seconds; ±s.e.) of non-escalated and escalated contests for manipulated and control males.