The visual perceptual range of a lizard, Tiliqua rugosa

The fragmentation of landscapes produces habitat gaps where the distance between visual landmarks may exceed the perceptual range of a species and impose navigational constraints. We estimated the visual perceptual range of the Australian sleepy lizard, Tiliqua rugosa, by releasing individuals in the centre of a cleared arena in high temperature conditions, with a 0.5-m-high bush placed either 10, 20 or 30 m from the release site. Lizards were more likely to locate those bushes and shelter under them when they were closer, and no lizards found a bush at 30 m. In addition, lizards were less likely to move from the release point when bushes were at 30 m than when they were at the two closer distances. These data suggest that for sleepy lizards the perceptual range for a 0.5-m-high bush is about 20 m. In the uncleared chenopod shrub-land where these lizards live, suitable shelter bushes are an average of 10.5 m from any point in their home range, well within their perceptual range.