Flat lizards Platysaurus intermedius wilhelmi occur on small discrete rock outcrops in Mpumalanga Province, South Africa. These rock outcrops are structurally simple and this, combined with the lizard's behaviour (ambush foraging in the open), make them ideal for field studies of anti-predatory behaviour. Lizards were approached in the field and how escape behaviour was influenced by habitat and age-sex class was recorded. Juveniles (c. 4 months of age) responded quite differently to an approaching human ‘predator’ compared with adult males and females (which responded similarly). Compared to adults, juveniles allowed a closer approach by the investigator; took longer to find a refuge and therefore fled further; were more likely to remain visible in the open and maintain visual contact with the investigator; and more likely to flee into vegetation when given the opportunity to take refuge in a crevice. We suggest that because a greater suite of predators (including arthropods living in rock crevices) feed on small juvenile lizards, this may affect their choice of refuge and result in the avoidance of crevices when chased. Finally, because juveniles were frequently found on small rock outcrops, the influence of rock outcrop area on anti-predatory behaviour was tested. Escape behaviour (time to refuge) was independent of rock outcrop area.