often coarse, but the chest and the belly are covered in soft fur; the fur of king cheetahs has been reported to be silky. There is a short, rough mane, covering at least along the neck and the shoulders; this feature is more prominent in males. The mane starts out as a cape of long, loose blue to grey hair in juveniles. Melanistic cheetahs are rare and have been seen in Zambia and Zimbabwe. In 1877–1878, Sclater described two partially albino specimens from South Africa. The head is small and more rounded compared to other big cats. Saharan cheetahs have canine-like slim faces. The ears are small, short and rounded; they are tawny at the base and on the edges and marked with black patches on the back. The eyes are set high and have round pupils. The whiskers, shorter and fewer than those of other felids, are fine and inconspicuous. The pronounced tear streaks (or malar stripes), unique to the cheetah, originate from the corners of the eyes and run down the nose to the mouth. The role of these streaks is not well understood—they may protect the eyes from the sun's glare (a helpful feature as the cheetah hunts mainly during the day), or they could be used to define facial expressions. The exceptionally long and muscular tail, with a bushy white tuft at the end, measures . While the first two-thirds of the tail are covered in spots, the final third is marked with four to six dark rings or stripes. The cheetah is superficially similar to the leopard, which has a larger head, fully retractable claws, rosettes instead of spots, lacks tear streaks and is more muscular. Moreover, the cheetah is taller than the leopard. The serval also resembles the cheetah in physical build, but is significantly smaller, has a shorter tail and its spots fuse to form stripes on the back. The cheetah appears to have evolved convergently with canids in morphology and behaviour; it has canine-like features such as a relatively long snout, long legs, a deep chest, tough paw pads and blunt, semi-retractable claws. The cheetah has often been likened to the greyhound, as both have similar morphology and the ability to reach tremendous speeds in a shorter time than other mammals, but the cheetah can attain much higher maximum speeds. Internal anatomy Sharply contrasting with the other big cats in its morphology,