Are calico and tortoiseshell the same?
Written by
Elin Eriksson
Reviewed by
Prof. David Walsh, Ph.D.Calico cats and tortoiseshell cats are different colorations that are often confused. Calicos have definite patches of three colors: black, orange, and white. The borders between these colors are sharp. Tortoiseshells have merged colors similar to a marble cake, with black and orange tones, and little to no white. The X-chromosome determines both colors with different effects.
Tortoiseshell Traits
- Brindled appearance: Black and orange swirled together
- Minimal white: Less than 25% white fur typically
- Genetic basis: X-chromosome color expression only
- Texture: Colors blend seamlessly throughout coat
Calico Traits
- Patchy distribution: Defined color blocks separated by white
- White requirement: At least 33% white fur always present
- Genetic basis: X-chromosome colors plus white spotting gene
- Contrast: Sharp boundaries between all three colors
These differing colorations result from genetic processes. Both require the presence of two X chromosomes for the dual pigment expression, which makes them almost invariably female. Tortoiseshell females require only the color genes, while calico females need one other gene, which is a mutation of the white spotting gene. This second gene destroys the pigment in certain areas and gives the characteristic white patches.
Recognition by sight is made easier by habit. The tortoiseshell cats show the effect of molten bronze and onyx, with white incidental. The calico is like splotches of paint on a white background. There are also dilute tortoiseshells and calico cats, blue-cream tortoiseshells, and soft gray and cream calicos in place of the black and orange shades.
There are Pattern hybrids, such as the torties. These are transitional forms demonstrating both mixed and patched areas. They appear due to partially expressed white spotting genes. About 15% of tortie-patterned cats will demonstrate these mixed characteristics. Showing the integrating spectrum between pure tortoiseshell and full calico expressions.
Care is the same. There are no special health problems with either tortoiseshells or calicos. They are beautiful patterns, but do not, in themselves, affect personality or longevity. Enjoy both of these lovely patterns as genetic wonders. Please provide them with proper nutrition and veterinary care, as they have no special care considerations. Their beauty comes from biology, not from special care requirements.
Read the full article: Cat Coat Patterns: A Visual Guide
