adult animal backside black Chapman's Zebra Chordata equidae Equus quagga chapmani graze herbivore horse leg mammal nature rear stripe stripes tail white zebra foal hoof mane young african bark black coats black skin Bray common zebra equids fast grant’s zebra grazers herbivores herbivorous herd herds individual patterns plains zebra social ungulates unique white fur white stripes black-&-white black-coats black-skin common-zebra grant’s-zebra greyscale monochrome plains-zebra striped white-fur white-stripes erect manes harems mohawk-like manes stiff manes erect-manes mohawk-like-manes stiff-manes