Animal Vision: Seeing the Earth’s magnetic field

We have known for a very long time that animals such as birds, turtles and butterflies use the Earth’s magnetic field to help them navigate on long journeys that span the globe. However, despite knowing that they can detect the magnetic field, we have no idea how they do it. We understand how the interaction of photoreceptors with light gives rise to vision, how receptors in our skin allow us to feel, how sapid molecules on our tongue allow us to taste and how olfactory sensory neurons in our noses give us our sense of smell. Beyond the human senses, we understand how some animals can perceive the polarisation of light and how others can detect electric fields. But how, or even which part of the body, bestows an animal with magnetoreception is currently a mystery. That is not to say there are no theories and, somewhat unexpectedly, some of them link magnetoreception with vision.