Behavioural aspects of many species may change through their ontogenetic trajectory. Mature males of the lizard Lacerta monticola present two types of colour phase, with bright green males being older, larger and more dominant than dull brown males. We hypothesized those ontogenetic differences in males competitive ability may lead to differences in spatio-temporal tactics. In a field study, we did not find differences in the size of the home ranges or core areas of green and brown males. However, after controlling for size, green males had more exclusive areas than brown males. Green males also had higher levels of conspicuous activities than brown males. Green and brown males had different spatio-temporal tactics within the day; green males used their home ranges more, were more active and had a higher degree of overlap with other males in the morning than in the afternoon. Brown males did not show these variations through the day. Green males participated in, and won more intrasexual agonistic interactions. Also, green males overlapped more extensively with areas of potential mates, and guarded females more often than brown males. These behavioural differences between males showed plasticity through ontogeny in the use of space, time and types of activity.