«Direction isn't something humans can detect innately. Some birds can, of course, and for them it's no less important than taste or smell are for us. In fact, lots of animals have cool, "extra" senses. Sunfish see polarized light. Loggerhead turtles feel Earth's magnetic field. Bonnethead sharks detect subtle changes (less than a nanovolt) in small electrical fields. And other critters have heightened versions of familiar senses — bats hear frequencies outside our auditory range, and some insects see ultraviolet light.»