Black Cats: Genetics, Myths and Adopting One

What makes a cat black?

Two copies of a recessive gene variant called non-agouti. In 2003 a team publishing in Current Biology traced it to a tiny deletion, just two DNA letters long, in the ASIP gene (agouti signalling protein). All 57 unrelated black domestic cats they tested from around the world carried two copies, and in a family of 89 cats the deletion and black coat were inherited together every time.

What the gene does is simple once you see a single hair. The UC Davis Veterinary Genetics Laboratory explains that the agouti protein switches pigment production between black and a lighter yellow-red, which gives a normal hair its bands. The non-agouti variant stops the switch, so each hair is one even colour. On a tabby, the banded background hairs are what make the stripes stand out; take the bands away and the whole cat fills in black.

Because the variant is recessive, a black cat needs one copy from each parent. That has three handy consequences:

• Two black parents cannot have tabby kittens, since both can only pass on non-agouti. They can still have blue (grey) kittens if both carry dilute.
• A tabby can carry black without showing it, so two tabbies can produce a black kitten.
• Black and ginger work differently. The orange gene overrides non-agouti, which is why a black mother and a ginger father can have ginger and tortoiseshell kittens alongside black ones. Our ginger cat guide explains that gene.

Blue (grey) is black lightened by the separate dilute gene. The rest of the colour switches, from dilute to white spotting, are set out in our guide to every moggy colour and pattern.

Why can you see faint stripes on a black cat?

Because the tabby pattern is still there under the black. Non-agouti hides the pattern; it does not delete it. A 2009 genetics study in the journal Genetics described non-agouti, non-orange cats as showing no pattern “other than occasional faint ghost patterns.” Owners often say they notice them in kittens or in strong sunlight, but we found no study measuring when they show.

Ghost stripes are harmless. They do not mean a black cat is “part tabby” in any useful sense, because every cat is a tabby underneath.

Why do some black cats turn rusty brown?

The clearest evidence points to diet. In a 2001 study in the Journal of Small Animal Practice, researchers at the University of California, Davis fed black cats diets low in the amino acid tyrosine. Their coats turned reddish-brown, the hair held less melanin under the microscope, and blood tyrosine was low. Black kittens born to mothers fed a tyrosine-deficient diet were reddish too. Diets high in tyrosine or phenylalanine kept or restored the black.

A follow-up in the Journal of Nutrition in 2002 measured the threshold. Cats fed less than about 16 g of phenylalanine plus tyrosine per kilogram of diet developed “red hair,” and the authors recommended at least 18 g/kg to keep a black coat black, well above what was then considered enough for growth. In plain words: the amount of these amino acids that keeps a kitten growing is not enough to keep a black coat fully black.

Two other explanations are often given: sun-bleaching in cats that bask a lot, and a browner tinge with age. Both are widely reported, but we found no study measuring either, so treat them as likely rather than proven. Show standards treat rust as a fault: the Cat Fanciers' Association British Shorthair standard asks for black with “no rusty tinge,” and the Oriental standard for ebony asks for a coat “free from any tinge of rust.”

What to do: if the change is sudden or patchy, the coat is dull or thin, or the cat is on a home-made or restricted diet, talk to your vet rather than adding supplements yourself.

Smoke or solid: what is the difference?

A smoke has a white undercoat; a solid does not. The Cat Fanciers' Association Persian standard describes a solid black as “dense coal black, sound from roots to tip of fur,” and a black smoke as “undercoat white, deeply tipped with black.” The Maine Coon standard uses almost the same words.

On a short coat, smoke can be hard to spot until you part the fur. If a rescue listing says “black smoke,” it is describing the undercoat, not a different personality or breed.

Which cat breeds come in black?

Only one breed is always black: the Bombay. The Cat Fanciers' Association says it was developed in Kentucky from 1966 by crossing a black American Shorthair with a Burmese, to look like a small black panther with gold to copper eyes. CFA calls it one of its rarer breeds, and it rarely appears in Australian rescue.

Many other breeds accept black as one colour among several. These are the ones we checked in the CFA standards:

In rescue, breed matters far less than you might expect. Almost every black cat Australian rescues list is a Domestic Shorthair, Medium Hair or Longhair, the shelter label for a moggy. A sleek black shorthair with copper eyes is usually not a Bombay, and a fluffy black cat is usually not a Persian or Maine Coon. Our guide to what a Domestic Shorthair is explains the label.

Where do the black cat superstitions come from?

Mostly from medieval Europe. The US National Library of Medicine's history blog traces the bad-luck idea to the Middle Ages, when black cats became tied to witches and the devil, and says the fear travelled to North America with the Puritans. It also notes the opposite traditions: English sailors thought a black cat that came aboard and stayed brought luck, and in Japan black cats are said to bring prosperity and bless a marriage.

In other words, the same black cat is lucky or unlucky depending on where you grew up. None of these beliefs says anything about the cat in front of you.

Do black cats really wait longer in shelters?

Sometimes. Shelter staff call it black cat syndrome, and researchers call it black cat bias. The published studies do not all agree, and the only Australian one we found points the other way. Here is what each study measured and found:

So the honest answer is that a black-cat penalty has been measured in some American shelters, it is not universal, and the size of the gap varies. In the Sydney study, black was the second most common colour after tabby, at about a quarter of the cats, and the stays of ginger, tabby, grey and tortoiseshell cats did not differ significantly from black cats'. The authors' own advice was that shelters should look at their own data.

The Jones and Hart finding is the most useful one for an adopter. If black cats lose out, a likely reason is that people find them harder to read, in a photo or across a room. That is a problem with the photo, not the cat. Ask the rescue for a video, or meet the cat in person.

Do black cats have a different personality?

No good evidence says so. The studies on colour and personality mostly measure what people believe:

• A 2012 online survey of 189 people, reported by UC Berkeley, found people rated orange cats friendliest and white and tortoiseshell cats least friendly. Black cats were given less extreme traits than other colours. The lead author said there was little evidence that the perceived differences actually exist.
• A 2016 UC Davis survey of 1,274 owners linked more reported aggression toward people to torties, calicos, black-and-white and grey-and-white cats. Solid black cats were not among the colours singled out. These were owner reports, not observed behaviour.

For a desexed rescue cat, its history and how it behaves with a foster carer are far better guides than colour, or sex: see male or female cat for what the research says there.

Tips for choosing a black cat from a listing

Black cats are hard to photograph, so the listing photo is a weaker guide than usual. A few things help:

• Read the description, not just the photo. Notes from a foster carer about how the cat behaves at home are worth more than any picture.
• Ask for a video or a second photo taken in daylight. It is a normal request.
• Meet more than one. Black cats often look alike on a page and are very different in person.
• Ask how long the cat has been listed. A cat that has waited a while may already have a well-known personality.

Rescue cats normally come desexed, vaccinated and microchipped, whatever their colour. For the steps, fees and state laws, read adopting a cat in Australia, and budget with what a cat costs. If you live in Sydney, our Sydney black cat adoption guide lists the local rescues.

Find a black cat near you

These pages show black cats listed by Australian rescues right now, with age, sex and desexing status, and a link straight to the rescue. They are refreshed regularly.

• Sydney: black cats in Sydney
• Melbourne: black cats in Melbourne
• Brisbane: black cats in Brisbane
• Perth: black cats in Perth
• Adelaide: black cats in Adelaide
• Anywhere in Australia: all black cats for adoption

Not sure a cat suits you yet? Try the dog or cat quiz, the what cat breed am I quiz and the adoption readiness check. If a kitten is on your list, kittens in Sydney and kittens in Melbourne include black kittens alongside every other colour.