animal brown caballus Chordata dolichohippus equidae equus free hippotigris horse mammal mammalia perissodactyla savage widlife wild wilderness wquus caballus adult Africa african ass Equus africanus gray graze grey herbivore leg mane nature Somali Wild Ass domestic domesticated farming livestock riding transportation working animals black equus grevyi equus quagga equus zebra texture white zebra backside Chapman's Zebra Equus quagga chapmani rear stripe stripes tail foal hoof young