Why Do Some Fruit Bats Have Color Vision?
06/12/2007 One would think bats don t need color, since most fly at night. That s what scientists thought, reported Max Planck Institute, until color-vision cones were found in some species. Some species have two cone types, giving them bichromatic vision, and some have only one, making them effectively color blind. Bats come in two orders: big and small. We usually think of the small microbats that live in caves and use echolocation, but the megabats, or flying foxes, do not use sonar. They fly at twilight or during the day. Both orders are amply supplied with the light-sensitive rods. The scientists found that some megabats have green and blue cones, but three species have only green cones. They surmised that these species, roosting in darker quarters of caves and trees and flying only in twilight, lost the use of their blue cones. One commented, A loss of blue cones is a rare event in evolution, it has been found in only a few mammals. Otherwise, the retinas of bats are normal for m
