Why do Siamese cats have dark points?

Why do Siamese cats have dark points? Because their pigment depends on temperature. Siamese cats carry a variant of the tyrosinase gene, which makes the enzyme behind melanin, and their version only works well where the body is cooler. So colour builds up on the ears, face, paws and tail, the cooler extremities, while the warmer body stays pale. It is one of the clearest examples of a gene and its surroundings working together, and it is the look we drew in our Siamese.

The colourpoint gene

The gene is often called the colour gene, and its scientific name is TYR, for tyrosinase. The Veterinary Genetics Laboratory at the University of California, Davis, describes the Siamese variant as producing pigment in a temperature-sensitive way: production falls in the warmer parts of the body, so pigment gathers in the cooler extremities. A related variant gives the Burmese its look, with colour spread more evenly and points only a little darker. A cat that carries one of each shows an in-between shade breeders call mink.

Why do Siamese cats have dark points? A map of warm and cool

Think of a Siamese coat as a heat map of the cat. The core of the body is warm, so the enzyme barely works there and the fur stays cream or ivory. The ears, nose, paws and tail lose heat faster, so the enzyme works and the fur turns dark. The mask on the face follows the same rule.

Born pale

Siamese kittens are born white or cream. Inside the mother, they are kept evenly warm, so no points form. After birth, the extremities cool and the points begin to show, often within the first week or two, then darken as the kitten grows. Owners also notice that the coat can shift a little with the seasons and with age, darkening over the years.

Seal, chocolate, blue and lilac

The points come in several shades. Seal point is dark brown to nearly black; chocolate point is a milk-chocolate brown; blue point is grey to slate; and lilac point is a pale grey with a pinkish tone. The body colour shifts to match, warmer behind seal and chocolate, cooler behind blue and lilac. Siamese cats also have blue eyes, part of the same colourpoint package.

Not only the Siamese

The colourpoint pattern turns up in other breeds too, such as the Birman, the Himalayan, the Balinese and the Tonkinese, and in mixed-breed cats that inherit the gene. So a cat with dark ears and a pale body is not always a Siamese, but it is always a colourpoint. Among our seven coats, the Siamese is the only colourpoint; the Tuxedo and the Calico show what white spotting does instead.

The shaved-patch effect

The same rule shows up in everyday life. National Geographic notes that when a Siamese has a patch of fur shaved, for example at the vet, the fur can grow back darker, because the bare skin is cooler; it may lighten again later. The coat also deepens as the cat ages.

Other animals with the same gene

Cats are not alone. Geneticists point out that many species carry a version of this Himalayan gene, including the Himalayan rabbit, as well as some rats, gerbils and mink. In each, colour gathers on the cooler ears, nose, feet and tail.

Our Siamese, embroidered

Our Siamese is seen from behind: a pale coat, dark ears and a dark tail, and a blue collar to match the eyes you can’t see. It is machine embroidered in three thread colours at the centre of the chest of a tee, a crewneck or a hoodie, or on the front of a tote, and made for you after you order. It belongs to Find your cat, seven coats from ginger tabby to tuxedo. For how the colourpoint fits among the other coats, read our guide to cat coat patterns.

Which piece to choose

The Siamese comes on four pieces. The heavyweight tee is 100% ring-spun cotton, garment-dyed, in sizes S to 4XL. The crewneck and the hoodie are a soft fleece of cotton with some polyester, in sizes S to 3XL. All three are a relaxed fit, so order your usual size, and the size guide lists every measurement in centimetres. The tote is one size, 38 × 42 cm. Its garments come in flo blue or blue jean, two blues chosen to echo the collar, and the tote in French navy. Every piece is made for you after you order, and each product page shows the expected delivery dates, with free tracked shipping.