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In species with reduced locomotory abilities, camouflage seems to be f a r more important than other behavioural tactics (e.g. running) to elude predatory attacks. In this study, we examined the effects of camouflage on escape decisions in the common chameleon Chamaeleo chamaeleon. The effectiveness of camouflage was assessed by the ability of humans to detect different sized chameleons placed on different backgrounds (vegetation of high and low density, defined here as open and dense bushes), both in the field and in photographs. Escape behaviour was analysed by simulating a predator attack (in our case, approach by a human). As expected, the probability of detection by a potential predator was size-and background dependent. In the field, detection time (but not distance) was significantly higher for chameleons of a given size perched on dense (Myoporum) than open (Retama) bushes. When using photographs, the probability of detection was higher for large (adult) chameleons perched on open (Retama or Nerium) bushes and lower for hatchlings perched on dense (Myoporum or Cupressus) bushes. Conspicuousness greatly influenced the escape tactics of individuals. Chameleons perched on more protected Myoporum allowed closest approach distances than those perched on less protected Retama. In general, antipredatory responses (defined here as 'first movement', 'fleeing', 'mouth opening' or 'free falling') occurred significantly earlier in the trial sequence in chameleons perched on clear Retama than those perched in Myoporum. Two antipredatory responses were size-dependent: juveniles and adults exhibited 'mouth opening' more frequently than hatchlings whereas 'free falling' was more frequently recorded for hatchlings, Our results suggest that size and vegetation greatly influence the risk of detection by predators and this variation influences an individual's decision about when and how to escape. 0 2001 The Linnean Society of London ADDITIONAL, KEYWORDS: crypsisescape decisionsinfluence of vegetationbody size effectscamouflagelizards.

Female common chameleons, Chamaeleo chamaeleon, show temporary body color changes during the reproductive season, probably in synchrony with their reproductive status. In a field study, the color changes of 21 radio‐tagged females were monitored for the apparent effects that three selected colorations (green body with yellow lines, green body with yellow spots and black body with yellow spots, abbreviated to GYL, GYS and BYS, respectively) had on the reproductive behavior of both sexes. In a field experiment, females naturally displaying GYL were artificially painted to resemble GYL (or control), GYS and BYS. They were released in the wild and the response of males was recorded. The frequency of male‐female behaviors, the pairing time and the outcome of male copulation attempts were consistent with the respective neutral (GYL), receptive (GYS) and gravid (BYS) functions of female color phases since a high percentage of copulations occurred during the short‐term GYS phase, whereas all copulation attempts by males were violently rejected during the BYS phase. In addition, BYS females also displayed specific behavioral postures to prevent matings. In the field experiment, the number of approaching males and the strength of the response by males were significantly higher for painted GYS females. The data show strong evidence that temporary body color changes in female common chameleons are associated with changes in their reproductive status and hence, function as signals used in inter‐sex communication.

Vertebrate males often show breeding colours that may function as reliable signals of status in intrasexual competition. In many lacertid lizards, males show a conspicuous row of small but distinctive blue spots that runs along their body side on the outer margin of the belly. However, no study has examined the role of these blue spots. We first analysed in a field population of the Iberian rock lizard, Lacerta monticola, the relationships between number of blue spots and some morphological traits, which are known to be related to malesÕ fighting ability. The number of spots seems to be an character showing ontogenetic change as large (generally older) males showed more blue spots than small (generally younger) males. Males with a higher body condition also showed a higher number of blue spots. Thus, a higher number of blue spots may be used to signal size, age or body condition. Many contiguous blue spots would result in a visual artefact consisting of a continuous blue band, which might be a reliable size-or condition-dependent signal in some social contexts. We further examined in the laboratory whether male characteristics are related to dominance status. In males with similar body size or age, those with relatively larger heads were more dominant, whereas the number of blue spots was not important. Moreover, the number of blue spots in nature was not related to relative head size. Finally, we experimentally manipulated the presence and the number of blue spots of intruding males, and examined the aggressive response of resident males. Intruder individuals manipulated to cover all their blue spots received a lower amount of aggression. However, males with different numbers of manipulated blue spots received a similar number of aggressive responses. These results suggest that, during agonistic encounters, the presence of blue spots, but not their number, may elicit aggressiveness. Thus, blue spots may serve to identify an individual as an adult male, and to enhance body size of larger males.

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