Tiger stripes are math!
As weird as it may seem, one model describes almost all mammal coloration patterns. All it takes to make an animal a certain color is the interaction of a couple of chemicals with the skin. One chemical stimulates melanin, causing darker coloration in the skin and fur of mammals, while another keeps melanin from being produced. These spread outwards through the body of the animal in the same way in every mammal….
The key to the differences in coloration is the fact that the chemicals spread outward in waves at different phases during the gestation period. Some start their move when the embryo is still tiny. Some start when it’s nearly fully grown. If the animal is tiny, no pattern will form, which is why there aren’t a lot of tiger-striped mice out there. If it’s huge, the chemicals jumble outwards and back, interfering with each other until they form a uniform color. This is why there aren’t any tiger-striped elephants.
And tigers? Their chemical waves move out at just the right time to form a series of peaks and valleys that lead to striped patterns on their fur. Leopards, though smaller than tigers, get hit with the waves at an embryonic stage at which they’re a little bigger than the tigers. The waves interfere enough to form spots on their bodies. Giraffes get hit at a bigger stage and form the large brown patches that we see on them.
Also, it depends on the shape and size of the body part, which is why spotted cats have striped tails. The original report is here:
This is really cool to know, that something as beautiful as the stripes on my beloved cat Tasha are an expression of math and physics, an interference pattern between chemical waves. And it might explain something about her brother Shadow. When he was a very small kitten, he had faint stripes of lighter and darker gray, but as he got older, the stripes vanished and he became a solid (and totally gorgeous) dark gray. Maybe the interference process was still ongoing.
It’s also useful to me as an SF writer and alien-creator to know this. This specific formula only applies to mammals, but the original article says that similar math can explain butterfly wings and striped fish. So maybe if I create some giant alien creature in a future novel or story, I’ll take care not to give it stripes or spots.