The Makgadikgadi Pans are made up of two massive salt pans, Ntwetwe and Soa, and their nearby open grasslands. Only a small part of the northwestern section of Ntwetwe Pan falls within the 2,575 square miles of the unfenced boundary. There are many smaller pans located throughout the south and east of the park. The surface of the pans consists of a flat layer of silt that turns into sticky mud during the summer rainy season. One of the interesting attractions of this reserve is the huge area of open grassland and the vegetable ivory palms (which dominate the landscape of the north sections). Game populations in this area are subject to considerable movement and migration, which is dictated by water and food supply. During the dry season the herds tend to focus on the west, in the vicinity of the Boteti River, but with the onset of the rains the animals spread to the east and north. Red hartebeest, blue wildebeest, eland, gemsbok, springbok and Burchell's zebra are the most common inhabitants of this area. All of the large predatory species: lion, cheetah, leopard, wild dog, and brown spotted hyenas are present here, as well.