Animals That Can Detect Things Human Senses Cannot

A desert ant can leave its nest, wander across a nearly featureless landscape searching for food, and still determine the direction home without following a marked trail. Species such as Cataglyphis use several navigational tools, including an internal process known as path integration. One crucial source of directional information comes from patterns of polarized light in the sky. Sunlight scattering through Earth’s atmosphere creates polarization patterns that change predictably in relation to the sun’s position, even when the sun itself is partly obscured. Specialized photoreceptors in the ant’s compound eyes can detect this information and use it as a celestial compass. The ant combines directional measurements with estimates of distance traveled, allowing it to maintain a running calculation of the route back toward its nest. Landmarks and learned visual scenes can provide additional information when available, so the animal is not dependent on a single sensory cue. Experiments that manipulate the apparent polarization pattern can alter the direction ants attempt to travel, revealing how strongly this invisible compass influences them.