An Arctic Fox poses alertly, showing off its striking dark fur. The image highlights the fox's posture and inquisitive gaze. This fox is called a blue morph, even though it is clearly brown. Unlike other morphs, the blue morphs don't turn white in the winter. This blue morph is a dominant gene, but the gene has a very low frequency. Thus, the morph is quite rare, except on islands, where it can become the predominant color in a small population.