Traveling in small groups, sedge-sliders' enormous pink biolights shine like lanterns in the gloom of a receding storm. At first they appear headless, but as the sky grows lighter small dark beaks appear from beneath their anterior flaps. These gradually extend until an entire head is visible. The newly-emerged black heads steam for a few moments in the frigid air until they cool off. These large creatures have evolved a unique means of keeping their bare heads protected during arctic storms, by retracting them deep into their insulated body cavities.