Zebra herd in Namib Rand Nature Reserve in Namibia. The thin grasses here have a rare speckled pattern known as "fairy circles", a phenomena that is poorly understood. Grasses seem to grow higher on the inner rim of the circles due to less competition for water on the inside of the ring. Scientists speculate that the barren area inside the circles may be the result of some kind of growth-inhibiting substance left in the ground by either insect colonies or root systems of plants that are no longer found in the area, but fungus, termites, and radioactivity have all been ruled out. Numerous studies have tested out different theories without reaching an answer.