The Role of Stereopsis in Prey Capture: Binocular Depth Perception in Green Anoles (Anolis carolinensis)

Anolis carolinensis, commonly known as the green anole, is a small, tree-dwelling lizard native to the southeastern United States. These lizards possess two foveae in each eye, allowing for specialized high-resolution vision. The central fovea facilitates detailed imaging of distant objects, while the temporal fovea enhances binocular depth perception for nearby targets. However, it remains unclear whether green anoles rely on full stereopsis-the perception of depth based on positional differences between images received by each eye. To investigate binocular depth perception in prey capture, we conducted experiments where anoles attempted to strike a stationary cricket held on a rectangular paper pad. In one condition, we covered one eye to assess the role of stereopsis. If anoles relied solely on stereopsis for depth perception, we would expect them to misjudge their strikes. Additionally, we monitored eye convergence to evaluate prey alignment on both foveae by attaching pointers to their eyelids. Eye convergence refers to the way the eyes work together to point inward at nearby objects. Our results revealed variability in capture strategies. Some anoles miscalculated their strikes when binocular vision was disrupted, supporting the role of stereopsis. However, many lizards successfully adjusted their capture strategy after initial misses, suggesting that while stereopsis contributes to depth perception, it may not be their sole mechanism for judging distance during prey capture.