Chief's Island, a vast tongue of sand comprising nearly 1000 square kilometers, is the largest land mass in the Okavango Delta, stretching from the southern Okavango to the permanent waters near Mombo. It is an extension of the mainland and, because it is slightly higher than the general level of the Delta, it never floods. The Boro River, which runs south-east through the center of the Okavango Delta, skirts the western boundary of Moremi Wildlife Reserve. It is called Chief's Island as this used to be the traditional hunting ground of Chief Moremi, but is now incorporated into the reserve and no hunting is allowed. It is home to a vast number of animals who benefit from the Kalahari Sandveld habitat with its close proximity to water. The arid interior of the island is covered by Mopane woodlands and acacia thorn-scrub interspersed with clay pans. This is where the large resident buffalo herds of the Okavango are often to be found as they prefer to drink from the rain-filled pans and give preference to the sparsely growing but sweeter grasses of the sandy areas rather than the coarser grasses with lower protein yield of the floodplains.