Eagles are the most sharp-sighted animals

A new computer gives zoologists an idea of the vision of different animals.

The human eye is not the best at differing between colours nor seeing in the dark, but in one way, we are the most excellent: sharpness. Scientists from the Duke University in the US have developed a computer programme that simulates animal vision and tested it on 600 species.

The sharpness is defined as periods per degree, or how many pairs of black and white lines the eye can make out within one degree of vision. The human eye has a resolution of 60 periods per degree, and if the lines are more densely packed, they will merge into a grey mass. The scientists evaluated the animal vision based on anatomy and entered the data into the computer programme which, well, visualises the vision of different creatures.

Most species have poorer vision than we do. Most fish and birds have a vision of about 30 periods per degree, but for many insects, the number is about 1. Primates see just as well as we do, and only a few birds of prey have sharper vision. The "winner" of the study was the wedge-tailed eagle, which can see 140 periods per degree.

One interesting finding: Butterflies cannot see the patterns on their own wings. Instead, the patterns scare off sharp-sighted enemies.