The dog who cannot hear you

A surprising number of dogs described as stubborn, dreamy or badly trained are simply not hearing the instruction. And a surprising number of the ones that are hearing it are only hearing it with one ear.

Deafness is a pigment problem

The inner ear needs pigment cells in order to work. Melanocytes — the same cells that put colour in a coat — make up part of the stria vascularis, the tissue that maintains the fluid the cochlea depends on. Where the genes producing large areas of white have also removed pigment cells from the inner ear, that tissue degenerates within the first weeks of life. The puppy is deaf on that side before it ever leaves the litter, and nothing can be done about it afterwards.

That is why deafness clusters in white-patterned dogs rather than scattering at random. Dalmatians are the most documented case, but the list runs through English Setters, Bull Terriers, Australian Shepherds, Border Collies, Catahoulas, harlequin Great Danes and plenty of others. Blue eyes and an absence of pigment around the ear both push the odds up further.

The double merle problem

Merle is the mottled, marbled coat pattern — the one in the photograph above. A dog with a single copy of the gene is a merle. A dog with two copies, which is what you get from breeding one merle to another, is a double merle: largely white, and at high risk of being deaf, blind, or both.

This is not bad luck. It is a breeding decision, and it is entirely avoidable. Any breeder pairing two merles either does not know what they are doing or does not mind. Ask about the coat pattern of both parents, not just the puppy in front of you.

The half you cannot see

Deafness in one ear is common and almost never spotted at home. The dog hears you, comes when called, reacts to the door. What they cannot do is work out where a sound came from — so they look the wrong way, or set off in the wrong direction, and it reads as scattiness. A puppy who seems fine but consistently turns to the wrong side is worth testing.

The test is the BAER — brainstem auditory evoked response — which measures the brain's electrical response to a click played into each ear separately. It is quick, it does not depend on the dog cooperating or understanding anything, and it is the only way to find a one-sided loss. Responsible breeders of high-risk breeds test whole litters as a matter of course.

The other deafness

Age-related hearing loss is a separate thing entirely, extremely common, and routinely mistaken for stubbornness, selective hearing, or the beginning of cognitive decline. An older dog who sleeps through your arrival, startles when touched from behind, or has started barking at a volume they never used to, may simply not be hearing themselves or you.

What to do with this

• Teach hand signals to every dog, from the beginning. A dog who already knows visual cues loses very little when their hearing goes, and it costs nothing to build in early.
• Ask for BAER results when buying a breed on the list, and be suspicious of a breeder who has not heard of the test.
• Walk away from a merle-to-merle litter. No price makes that a good idea.
• Approach an older dog where they can see you. A startled deaf dog is not a grumpy dog.
• Keep a deaf dog on a lead near roads, and put it on the tag. Beyond that they live entirely ordinary lives — deafness is a management problem, not a tragedy.