they curve toward the nostrils, while the stripes above the front legs split into two branches. On the rump, they develop into species-specific patterns. The stripes on the legs, ears and tail are separate and horizontal. Striping patterns are unique to an individual and heritable. During embryonic development, the stripes appear at eight months, but the patterns may be determined at three to five weeks. For each species there is a point in embryonic development where the stripes are perpendicular to the dorsal line and spaced apart. However, this happens at three weeks of development for the plains zebra, four weeks for the mountain zebra, and five for Grévy's zebra. The difference in timing is thought to be responsible for the differences in the striping patterns of the different species. Various abnormalities of the patterns have been documented in plains zebras. In melanistic zebras, dark stripes are highly concentrated on the torso but the legs are whiter. "Spotted" individuals have broken up black stripes around the dorsal area. There have even been morphs with white spots on dark backgrounds. Striping abnormalities have been linked to inbreeding. Albino zebras have been recorded in the forests of Mount Kenya, with the dark stripes being blonde. The quagga had brown and white stripes on the head and neck, brown upper parts and a white belly, tail and legs. Function The function of stripes in zebras has been discussed among biologists since at least the 19th century. Popular hypotheses include the following: The crypsis hypothesis suggests that the stripes allow the animal to blend in with its environment or break out its outline so predators can not perceive it as a single entity. This was the earliest hypothesis and proponents argued that the stripes were particularly suited for camouflage in tall grassland and woodland habitat. Alfred Wallace also wrote in 1896 that stripes make zebras less noticeable at night. Zebras graze in open habitat and do not behave cryptically, being noisy, fast, and social. They do not freeze when detecting a predator. In addition, lions and hyenas do not appear to perceive the stripes when they are certain distance away during daytime, thus making the stripes useless in disrupting the outline. Stripes also do not appear to make zebras more difficult to find than more solidly coloured animals of similar size, and predators may still be able to detect them by scent or hearing.