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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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Sex recognition is based on color signals in many species of lizards. However, olfactory stimuli are also clearly involved, and many species might rely primarily on chemoreception. We aimed to examine whether color pattern or odors, or a combination of both factors, induce the aggressive response of males of the lizard P. hispanicus. We experimentally manipulated the coloration and odor of male P. hispanicus, thereby creating groups with all combinations between coloration and odor of males or females. Using data from staged encounters, we compared the responses of resident males to the experimental groups of manipulated males and their response to unmanipulated individuals (males and females). Responding males reacted significantly more aggressively to intruders with male odors independent of their coloration, whereas intruders with female odors did not elicit aggressive responses but were preferentially courted, irrespective of their actual sex and body coloration. In addition, intruders with female odors elicited a higher number of tongue-flick explorations than male odor ones. Comparisons with unmanipulated male and female intruders agreed with these expectations. Therefore, at least at close range, odoriferous cues seem to be more important than color patterns in sex recognition and intrasexual aggression by male P. hispanicus. We suggest that this might be a pattern commoner than expected in many species of reptiles. Aggr. Behav. 28:154-163, 2002.

The functional explanation of nonbreeding territories in birds was analyzed in a migratory population of Robins (Erithacus rubecula) over-wintering in southern Spain. The behaviour of ringed territorial Robins was compared with that of Robins classified as floaters, ringed or not, during the winter of 1992-1993 to test two non-exclusive hypotheses. First, the good feeding patch hypothesis, that territories are the most profitable feeding areas, is not supported because body condition (fat score, body mass and body condition index) and feeding rates did not differ between owners and floaters. Second, the antipredation hypothesis, that owners select protected areas with good cover to reduce mortality, does account for the maintenance of winter territories since owners spent a higher percentage of time hidden and were able to forage in lessexposed areas (i.e. closer to shelter) than floaters. Consequently, the winter territory of Robins should not be interpreted as a long-term defense of the most rewarding foraging patch. Instead, a good refuge and shelter seem to be the most important properties of territories. Thus, by attacking the intruders, owners are defending a safe foraging area close to shelter. The anti-predation benefits (i.e. a familiar and safe foraging area as well as a good roosting place) would explain per se the maintenance of winter territories in Robins and the intense competition with conspecifics and other ecologically similar species wintering in the Mediterranean.