The island fox (Urocyon littoralis) is the largest of the Channel Islands' native mammals. A descendent of the mainland gray fox, the island fox evolved into a unique species over 10,000 years ago. The island fox has similar markings to its ancestor, but is one-third smaller.

Environmental and ecological factors such as drought or food scarcity may have contributed to the natural selection for a smaller size. At 12 to 13 inches in height and 4 to 5 pounds, the island fox is about the size of a housecat. Island foxes have gray coloring on the back, rust coloring on the sides, and white underneath. The face has a distinctive black, white, and rufous-colored patterns.