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Matthew Kramer and Enrique Font

Abstract

Display repertoire analysis requires and unbiased estimate of the number of different displays. Anolis lizards, with easily quantifiable visual displays, provide a system amenable to determining display repertoire size. We used multivariate clustering techniques to classify Anolis equastris headbobbing displays. Forty displays, to conspecifics and mirrors, were graphed and 23 variables from each were used in a cluster analysis. Displays were classified into four distinct groups and a single odd display. The most important variables for classifying displays, assessed with a stepwide discriminant analysis, were associated with the general cadence, number of headbobs, and location of large and small headbobs. Most headbobbing displays ended in lateral head movements, possibly arising from ritualized mouth-wiping. All displays analyzed were apparently aggressive ("threat") displays, suggesting a rich display repertoire for this species but leaving unexplained the reasons so many display types are used. Social and defensive displays, while sharing a number of motor patterns, are readily distinguished by the long duration of dewlap extension and gaping in defensive behavior.

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Guillem Pérez i de Lanuza and Enrique Font

Iridescence is a visual property of those surfaces that change in colour with viewing angle. Iridescence has been rarely reported in reptiles, but some snakes and lizards show this type of coloration. Here we study the effect of different angles of light incidence and observation on the spectrophotometrically assessed reflectance of dorsal coloration in the lizard Podarcis muralis. The results demonstrate clear angle dependence of several colour parameters. In particular, different angles of light incidence and observation result in changes in hue of more than 30 nm. This suggests that lizard dorsal coloration may be perceived, depending on viewing geometry, as being of different colours by a wide range of potential observers. Functional implications of iridescence in dorsal coloration are discussed.

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Enrique Font and Guillem Pérez i de Lanuza

Abstract

The evolutionary significance of lacertid colourations is relatively unexplored. However, several studies have demonstrated signalling by means of bright green colouration in Swedish Lacerta agilis males during the breeding season. Unfortunately, most of these studies have been based on human colour perception that differs in several ways from that of lizard. An important difference between human and lizard colour vision is the presence of an ultraviolet (UV) sensitive cone in lizards. The available evidence suggests that male sand lizards colorations do not reflect UV wavelengths, at least in Swedish populations. However, this study, based on objective (spectrophotometric) measures of Pyrenean L. agilis, revealed a secondary reflectance peak in the UV in male green colouration. This secondary peak increases sexual dichromatism and male conspicuousness. Moreover, it could have a social signalling function as do similar UV reflecting patches in other lizard species.

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Miguel Carretero, Enrique Font, Ester Desfilis and Diana Barbosa

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Enrique Font, Martha Bohórquez-Alonso and Miguel Molina-Borja

Abstract

In lizards, site selection is related to the acquisition of resources such as refuges, mates or prey, but also to the exploitation of sites suitable for thermoregulation. The latter process may be affected by lizard posture and body axis orientation in relation to the sun as a way to optimize heat exchange throughout the day. Specific postures and body orientations could also contribute to more efficient signal transmission in social contexts. In this paper we analyze activity and body axis orientation of adult males and females of the lacertid Gallotia galloti in two localities of Tenerife with different structural habitats. We performed transects at both sampling localities in the morning and at midday during May and June of three years (2002-2004). The numbers of lizards detected per unit time during transects at both localities were similar; however, significantly more males than females were detected. Moreover, more lizards were found oriented parallel or perpendicular to the sun than in alternative (oblique) orientations. Heating rates were not different for copper lizard models oriented parallel or perpendicular to the sun, neither in the morning nor at midday, and there was no significant relationship between air temperature and lizard body orientation. This suggests that lizard body orientation is not constrained by thermoregulatory requirements. We discuss alternative hypotheses and conclude that body axis orientation in G. galloti lizards may reflect a compromise between the conflicting demands imposed by thermoregulation and social communication.