To check this out, I spent hours at the Oakland Zoo, often surrounded by school kids on field trips, to observe the different animals," said Banks. "Sure enough, when goats, antelope and other grazing prey animals put their head down to eat, their eyes rotated to maintain the pupils' horizontal alignment with the ground."
On the other side of the Atlantic, study co-author Gordon Love, a professor of physics at Durham University, found this same pattern when observing sheep and horses at nearby farms. Grazing animals' eyes can rotate by 50 degrees or more in each eye, a range 10 times greater than human eyes, the researchers said.