Unlike humans, squirrels possess peripheral vision as sharp as focal eyesight. Whereas people have only 2º high-resolution acuity, squirrels see well at some 50º; an astounding feat.
This follows from the squirrel’s rapid detection of visual stimuli and quick response time, as observed by its phenomenal ability to avoid predators. ~ Canadian physicist Dafna Sussman
Peripheral vision acuity is particularly puzzling considering that the squirrel eyeball has a construction similar to humans.
The squirrel’s visual acuity is likely dictated by its photoreceptor sampling. Such sampling is determined by the spatial distribution of the photoreceptors in the retina. The photoreceptor spacing of the ground squirrel can be assumed to be similar to that of other diurnal mammals, which is approximately 3 µm in the central retina. This distribution restricts the data sent to the brain, thereby limiting the neural image reconstruction process, and the final image perceived by the brain. ~ Dafna Sussman
Purely physiological explanation for a squirrel’s excellent peripheral vision is impossible.