Bats see colour through their ears and dogs through their nose

Photons ravel fast in straight lines, and can be focused with huge precision. This provides the opportunity to compute highly detailed, accurate information about the world. We are familiar with this, and we take it for granted that our eyes and associated brains enable us to navigate our way around obstacles at high speed, and hit a fast moving target like a tennis ball. We really notice the difference when darkness reduces us to helpless stumbling.

But there is a living to be made during the dark half of the day-night cycle, and it is now well known that bats have evolved the capacity to “see” without light, using their highly tuned ears rather than eyes (indeed the more specialised bats have all but completely lost their eyes). Echoes of high pitched sounds are not quite as good as well focused light but, with suitable processing in the brain, they enable the bat to fly at high speed between stretched wires without getting injured, and to catch insects on the wing, all in total darkness. Toothed whales have evolved the same “echolocation” skill (especially highly developed in river dolphins swimming and hunting in murky water where seeing is almost impossible) and by two separate groups of cave-dwelling birds.