Cuttlefish use polarized light to create a dramatic mating display invisible to humans

Many organisms leverage showy colors for attracting mates. Because color is a property of light (determined by its wavelength), it is easy for humans to see how these colors are used in animal courting rituals. Less obvious to humans is the polarization of light—a property of light related to the direction the wave is oriented in. Humans can't perceive polarization, which may be why we weren't aware of the interesting way cuttlefish use it to attract mates.