Whiting, MJ, JK Webb, and JS Keogh. 2009. Flat lizard female mimics use sexual deception in visual but not chemical signals. Proc R Soc B. Published online. Doi:10.1098/rspb.2008.1922.

In this study researchers studied Augrabies flat lizard (Playsaurus broadleyi) males that become sexually mature but retain a female appearance shared by all immature individuals of this species (the researchers called these individuals she-males). These males lack UV-reflective throat patches present in typical males (called he-males in the paper) and instead are believed to be visually mimicking females. The UV throat patch of these lizards is believed to be an honest signal. This deceptive signaling appears to reduce aggression from other males and may allow these cryptic males to sneak copulations with females within another male’s territory. All males eventually develop typical male coloration but the number of adult males may influence the proportion of female-colored males. The authors believe this indicates that this alternative mating strategy is frequency dependent. Individuals that appear female are first identified visually by males from a distance. When the males approach they may being to court and during courting the flanks or cloaca is subjected to tongue flicks, this is likely done to determine reproductive status through chemosensory analysis. Researchers wanted to determine if males that maintained female coloring would also generate dishonest chemical signals.

Studies were performed in the wild at the Augrabies falls national park in Northern Cape Province, South Africa. Hexane was used to remove surface lipids from lizards which were then applied to other individuals. The resulting groups were unmanipulated control females, hexane control females (with no scent), hexane females with she-male scent, unmanipulated control she-males, hexane control she-males, and hexane she-males with female scent. Individuals were then exposed to free-ranging he-male lizards and the responses were studied, including time to first tongue flick (TF) and number of TF’s, length of courting time, and whether copulation or aggressive behaviors were attempted.

Researchers found that he-males readily courted test lizards from all the treatment groups equally. Courtship continued for all those individuals that had a female scent regardless of male or female identity. Individuals with the male scent or no scent had the lowest frequency of courtship. Copulation attempts were also greater for those individuals displaying a female scent. 18% of she-male scent-labeled females were met with aggressive response from free ranging males versus none of the control females. Researchers say this may explain why she-males avoid he-males, visual deception functions from a distance but chemical cues are difficult to mimic because it is tied to internal signals.

Researchers studied a form of mimicking that appears to be frequency-dependent, a concept related to game theory, as discussed in class. In frequency-dependent scenarios payoff depends on what strategy other individuals choose. Here it is theorized that if there are a large number of he-males competition is too great and it pays for young males to produce dishonest signals. One reason discussed in lecture that deceit might exist even in an evolutionarily stable state is through perceptual error by receivers that allows cheaters to remain undetected. This study seems to confirm that this sort of mechanism is effective in allowing cryptic males to remain unidentified by other males, as long as the cryptic males are able to maintain a distance. Returning again to the issue of signal origin, the visual signal precursor in these cryptic males is the immature stage of flat lizards where males lack UV throat patches and are essentially visually indistinguishable from females. Cryptic male flat lizards are merely delaying one aspect of maturity in order to create a dishonest signal.

The authors discussed other ideas mentioned in lecture that signal efficacy depends on the environment and a receiver’s sensory system, another concept mentioned in lecture. The authors theorize that this is why many animals use multiple signals. Here we see that these multiple signals can indeed have a major impact, one of the signals is manipulated even as another remains honest.