The benefits of pupil orientation.

This is kinda neat, from the current issue of Science Magazine:

 

Slit-eyed animals have either vertical or horizontal pupils. It is unclear whether one orientation conveys any sort of competitive advantage over the other, and if so, under what circumstances. Banks et al. suggest that the optics of vertical pupil slits generally benefit predators, whereas the optics of horizontal slits benefit prey. Vertical slits are better for estimating object distance and distances along the ground—perfect for a predator stalking its prey. In contrast, horizontal slits are better for seeing objects on the horizon—ideal for prey seeing an approaching predator and deciding which way to flee.