The animal on the cover of Ubuntu: Up and Running is an addax (Addax nasomaculatus). It is more commonly known as the screwhorn antelope because of the crooked horns that adorn both sexes of this endangered species. Females' horns can grow to be more than 2.5 feet high, while males' horns can reach as high as 4 feet.The addax's coat changes colors with the seasons; in the winter, it is a grayish-brown and its hind legs are white, and in the summer, its coat is completely white or sandy-blond. Its beard and red nostrils are also characteristic of its appearance. Its hooves are flat with strong dewclaws-vestigial digits on the feet of many mammals, birds, and reptiles-that help them walk on, rather than sink into, the sand. The addax lives in isolated sections of the Sahara desert and is nocturnal, as temperatures are coolest at night. During the day, it rests in a bed it has dug with its forefeet, ideally hidden in the shade provided by boulders or bushes. It feeds on Aristida and Parnicum grasses, eating only specific parts of each. Aristida grass thrives with only the slightest bit of humidity and rain, so it is a dependable resource for the addax, and the seeds of the Parnicum grass are high in protein. Able to survive in the drastic desert conditions, addax can live without water almost indefinitely. In fact, they rarely, if ever, drink water; they get sufficient moisture from their food. Addax herds can contain as many as 20 animals, both male and female. Its hierarchy appears to be based on age, as herds are characteristically led by the eldest male. There are fewer than 500 addax in the wild. Much of their habitat was destroyed for commercial purposes and the animal itself is hunted for leather. The addax is much slower than other antelope species and is thus an easy target for hunters with motorized vehicles.