A white cat is white for 1 of 3 different genetic reasons, and only 2 of those 3 put hearing at risk. The coat does not damage the ear; the absence of pigment-producing cells in 1 strip of the inner ear does. A white cat with 2 blue eyes is the highest-risk combination, and the test that settles it takes about 15 minutes and can be run from 5 to 8 weeks of age.
Three loci, one of them a decoy
The W locus, dominant white, produces a cat that is white from nose to tail tip with no patches at all; it acts on the KIT gene and suppresses pigment cell migration across the whole skin. The S locus, white spotting, gives the piebald cat: white paws, a white chest, a white blaze, anywhere from a 2 cm locket to 90 percent of the body. The C locus is the decoy: albino and colourpoint cats are pale because tyrosinase cannot make pigment at body temperature, not because melanocytes are missing.
That third mechanism is why a colourpoint Siamese with a nearly white body hears perfectly. Its melanocytes are present and working in the ear; they simply cannot make visible pigment in warm tissue. Deafness tracks the absence of cells, not of colour.
What melanocytes do inside the ear
Melanocytes in the stria vascularis, a layered strip of tissue on the outer wall of the cochlear duct, help generate the endocochlear potential, a positive voltage of roughly 80 mV that drives the hair cells. Remove those cells and the potential collapses, the hair cells stop firing and then degenerate. In the affected ear the loss is progressive over the first 2 to 4 months, so a kitten that responds at 6 weeks can be unresponsive at 16.
The same cell line supplies the iris, which explains the blue eye: an iris with almost no melanin, coloured by light scattering. Blue eyes and deafness therefore travel together as 2 symptoms of 1 missing cell population, not as cause and effect.
The risk ladder, without a percentage
What matters clinically is 3 tiers: a white cat with 2 blue eyes sits at the top, 1 blue eye and 1 green or gold eye in the middle, 2 non-blue eyes at the bottom but never zero. A cat with white ears on a coloured body can be deaf in 1 ear only.
Unilateral deafness is the tier owners miss, because those cats function well: they turn to the wrong side, sleep through a call from the deaf side, and startle when a hand appears from that direction. A cat that hears in 1 ear is not a quiet cat; it is a cat compensating.
When to run BAER
BAER, the brainstem auditory evoked response, is the only test that answers the question. The window is 5 to 8 weeks: the ear canal opens at 10 to 14 days, air conduction matures over the next 3 to 4 weeks, and by 6 weeks the response is stable enough to trust. Test at 6 to 8 weeks and repeat at 12 weeks if a result is equivocal.
The test needs no anaesthetic in most kittens: 3 electrodes on the scalp, a click through a small earphone, each ear separately, 10 to 20 minutes for the pair. Clicks run at 70 to 90 dB nHL, roughly 1,000 to 2,000 per ear, over a 10 ms window.
What the trace shows
A normal ear produces 5 waves in the first 10 ms, labelled I to V, each generated by 1 relay from the cochlear nerve to the brainstem. Wave V is the one that decides: present at 70 dB, still present as the level is lowered, and the threshold is the lowest level that still produces a repeatable wave. A deaf ear gives a flat line at every level, and that flat line, not the absence of a startle, is the diagnosis.
Five sounds, three distances, at home
Home testing cannot replace BAER, but it flags a kitten for testing and tracks 1 ear over time. Use 5 sounds: a set of keys, foil crinkled, a squeaky toy, a hand clap and a vacuum cleaner at 70 to 75 dB. Test at 1 m, 3 m and 5 m, always from behind and out of sight, 3 trials per sound, and count a response only when the ears flick, the head turns or the pupils dilate within 1 second.
Run it on carpet, never hard floor: a cat feels footsteps through its paws and will look up at a sound it never heard. A kitten that fails 2 of the 5 sounds at 3 m gets booked for BAER, not rehomed.
| Locus | Gene | White on the body | Melanocytes in the ear | Risk score, 0 to 3 | BAER week |
|---|---|---|---|---|---|
| W, dominant white | KIT | 90 to 100 percent | Reduced or absent | 3 | 6 to 8 |
| S, high white | KIT | 50 to 90 percent | Reduced in white ears | 2 to 3 | 6 to 8 |
| S, low white | KIT | 5 to 30 percent | Normal | 1 | 8 |
| C, colourpoint | TYR | 60 to 80 percent pale | Present and functional | 0 | 0, not needed |
| No white | None | 0 percent | Normal | 0 | 0, not needed |
Living with a cat that cannot hear
A deaf cat is a visual cat: train 3 to 5 hand signals, always in the same order: palm up for come, a flat palm for stay, a point for food. Approach from the front or the side within its field of view, never from behind, and stop 1 m away so your shadow arrives before your hand. Stomp once on the floor to call it from another room; the vibration travels through the joists and reads as a signal.
Indoors is the safe default: a deaf cat that slips out cannot hear a car, a dog or a gate, so a breakaway collar with a tag, a microchip and a netted balcony are the 3 items to install before 6 months. Keep the routine fixed: same feeding spot, same 2 or 3 sleeping places, same hand signal for dinner.
White skin is the other long-term item. The pinnae and nose bridge hold little pigment, take ultraviolet damage, and squamous cell carcinoma on ear tips is real in white cats. Keep the cat in during the 10:00 to 16:00 window in summer and check the tips monthly for a scab that has not healed in 2 weeks. A white coat also hides nothing, so the 2 seasonal sheds are the best time to spot a new crust or a thinning patch. A baseline blood count at the first annual visit, read with the white cell differential, gives you a number to compare against later.
Before the kitten comes home
- If there is no result, book the test for 6 to 8 weeks, not 4.
- Ask for a BAER report with both ears labelled.
- Run the 5-sound check at 1 m, 3 m and 5 m on carpet, 3 trials each.
- Fit a breakaway collar with a tag, and microchip by 6 months.
- Check ear tips monthly, and keep summer sun off the nose bridge.
Frequently asked
Are all white cats deaf?
No. White comes from 3 different genetic routes and only 2 of them, dominant white and white spotting, remove pigment cells from the inner ear. A colourpoint cat with a pale body has all its melanocytes and hears normally. Risk rises with 2 blue eyes and with white ears, and it is highest in a cat that is white from nose to tail tip, but the only way to know is a BAER test.
At what age can a kitten have a BAER test?
The reliable window is 5 to 8 weeks, with 6 to 8 weeks being the usual booking. The ear canal opens at 10 to 14 days, air conduction matures over the following 3 to 4 weeks, and before that the response is too immature to trust. If a result at 6 weeks is equivocal, repeat it at 12 weeks, and test each ear separately so unilateral deafness is not missed.
Can you test a cat's hearing at home?
You can screen, not diagnose. Use 5 sounds, including keys, foil, a squeaky toy, a clap and a vacuum at 70 to 75 dB, at 1 m, 3 m and 5 m, always from behind and out of sight, 3 trials each. Do it on carpet, because a cat feels footsteps through its paws and will look up at a sound it never heard. Failing 2 of 5 sounds at 3 m means booking BAER.