Visual acuity and signal color pattern in an Anolis lizard.

Anolis lizards communicate with colorful dewlaps that often include detailed patterns. We measured the visual acuity of Anolis sagrei. Lizards viewed a checkerboard pattern of red and yellow-green squares that were too small to resolve, and thus appeared uniform in color. We quickly replaced the center portion of the display with a pattern of larger squares. If the new pattern could be resolved, the lizards perceived a change in color and reflexively shifted their gaze toward the target. The acuity threshold was 1.21 cycles deg-1 We also calculated acuity based on published anatomical data for Anolis carolinensis It was similar to that of A.sagrei for the visual periphery. Foveal acuity was 10 times greater. We approximated the effects of viewing conditions on the visibility of fine details of a conspecific's dewlap. For peripheral vision, no detailed patterns were visible at ≥0.5 m. For foveal vision, color-pattern details were visible at 1.0 m.