We see the word ‘agouti’ used a lot in the world of cats, particularly the world of cat breeders. This is because it is a word that indirectly refers to a very common type of coat; those with the tabby pattern. These are ticked, classic (blotched), striped (mackerel) and spotted.
In the cat world ‘agouti’ refers to a gene which, as I understand it, encodes the agouti-signalling protein which controls how colour pigment is deposited in the hair strand as it grows from the follicle.
As hair grows in its follicle, the pigment ‘eumelanin’ (melanin) is created in cells called melanocytes. As the amount of agouti-signalling protein is increased, melanin (dark brown colour) production is decreased (inhibited) which results in a shift to the production of phaeomelanin (yellow colour). The agouti gene also slows production of phaeomelanin but less so.
This results in banding along the hair strand and the tabby pattern which is black or very dark brown at the tip and yellow at the base or lower down on the hair strand.
The process gave rise to the wild-type tabby appearance of many wild animals as it is good camouflage which aids survival. Nature through evolution created this process.
It seems that the origin of the word ‘agouti’ comes from the species of rodent called the ‘agouti’ which has the ‘ticked’ tabby coat (in cat breeder language). And the agouti animal got its name from one of two South American indigenous languages: Guarani or Tupi in which the name is aguti, agouti or acuti.
Perhaps the best-known cat to have the wild-type ticked tabby coat is the jaguarundi while the best-known domestic cat to have this coat is the Abyssinian. The domestic cat’s tabby coat is inherited from the North African wildcat, the ancestor to the domestic cat. For the first few thousand years of cat domestication the only coat available was the faint spotted tabby. All the illustrations of domestic cats from Ancient Egypt are mackerel tabbies.
Through domestic cat evolution the mackerel (joined spots) and blotched tabbies developed. The latter emerged in the 19th century (blotched tabby gene tb combined with modifier genes). Throughout, the agouti gene was at work. Other modifier genes create the differences in tabby pattern by varying the way the dark bands of pigment are presented at the tip of each strand.