To determine the effect of environment and behaviour on locomotor activity, we explored sex-based differences in activity patterns before and after mating in the monogamous Australian sleepy lizard Tiliqua rugosa. We obtained continuous records of lizard step counts in the field for two 9-month activity periods. Lizards moved infrequently in both periods and were active for an average 13.2 (se 0.8)% of the day (07:00–20:00 h). Both sexes significantly reduced activity during drought and outside the spring activity period. Drought in the 2002/2003 period resulted in little reproductive activity, with no sex difference in activity. In early spring of the following period, with normal rainfall and food, males on average took significantly more steps per day, moved significantly faster for longer and covered nearly twice the distance each day as females. Males moved significantly faster in the mornings. Daily activity of both sexes had a unimodal peak around midday in early spring, shifting to distinctly bimodal patterns later in spring and early summer. In the 2-month pairing period before mating, when resource levels were high, the two sexes adopted different foraging strategies: males switched to a time maximization strategy, whereas females continued with an energy maximization strategy. After mating, females were significantly more active than males, with higher levels of activity in the afternoons. Males may be more active than females before mating because of multiple tasking in males, searching for extra pair matings, defence against rival males or as a signal of vigour by males to females.