Okapi are sexually dimorphic (2 distinct gender forms). Females are slightly taller/larger. Males have hide-covered ossicones (hornlike knobs), while females have bony bumps or hairy whorls. They have compact, dark brown bodies with downward sloping hindquarters. Their hindquarters, rump, and upper legs are marked with white stripes on a dark brown background, which make them difficult to see in the light and shadow of the forest.