Snakes' slit pupils help ambush prey

Vertical pupils help nocturnal snakes to hunt

source: New Scientist vol 207 no 2773, 14 August 2010 p18

Richard Shine from Sydney University, Australia, has found that nocturnal snakes are more likely to have vertical pupils, while round pupils are more typical of diurnal snakes. He looked at 127 species, luinking hunting behaviour and pupil shape. Snakes with slit pupils benefit from a deeper focus field, allowing them to keep still and maintain prey in focus. This helps nocturnal snakes to lie in ambush, while diurnal snakes tend to stalk prey.