Q: Why do some cats have white bellies and/or feet, while others have the same solid color or striped pattern across their entire bodies?
A: It all starts with melanocytes, cells that contain a pigment called melanin, found in the kitten embryo when it’s just a tiny sphere.
The melanocytes congregate on the outer surface of the embryo, where the skin and fur will form, along what will become the kitten’s back. As the embryo develops, the melanocytes migrate along the surface toward what will become the kitten’s belly and feet.
If many melanocytes divide quickly, enough of them reach the kitten’s underside to produce color everywhere. But if they divide slowly, there aren’t enough melanocytes to reach the underside of the embryo, and the fur on the tummy and/or paws will remain white, devoid of pigment.
I have a handsome tuxedo cat, which means he is black with white fur on his chin, chest, belly and paws. It looks like he’s wearing a black tuxedo with a white shirt—and white socks, surely a fashion “faux paw.” Now you know how his tuxedo color pattern came to be.
Look closely at dogs and many other species, and you’ll see similar color patterns.
Lee Pickett, V.M.D. practices companion animal medicine. Contact her at firstname.lastname@example.org.