Though most Dalmatians have normal hearing in both ears, some Dals are totally deaf. In the early 1980s, it
was discovered that some Dalmatians hear in one ear but are deaf in the other. These dogs are said to have
unilateral (one sided) hearing, and are also called unilaterals, or unis. The hearing status of a Dal can be
determined by BAER (Brainstem Auditory Evoked Response) testing. Hearing testing is now available in most
areas, and breeders can test their litters before puppies are placed. [For information on BAER hearing
testing, see hearing.html.]
If a Dalmatian will be deaf in one (or both) ears, the deterioration occurs when the puppy is very young.
If an ear is shown to hear normally on a BAER test when the puppy is a few weeks old, that ear will remain
the same throughout the dog's life - hearing will be normal. If the BAER test shows an ear is deaf, that
condition is permanent. As dogs age (just like humans), geriatric hearing loss occurs, but no sooner in a
unilateral hearing Dal than in a bilaterally hearing Dal. A traumatic event that could cause hearing loss
(long-term severe untreated ear infections, being too close to an explosion, etc.) would probably cause
damage to both ears in a bilateral dog as well as damaging the working ear of a unilateral hearing dog. It's
unlikely that a uni would become totally deaf except at an advanced age, at about the same time bilateral
dogs would lose their hearing too. Otherwise, the normal hearing ear of a unilateral Dal should function
perfectly without deterioration.
The main difference between a Dalmatian that hears bilaterally and one that has unilateral hearing is that
the unilaterally hearing dog does not have directional hearing. Dogs - and other animals, including humans -
can locate sounds because the sound reaches one ear a fraction of a second before it reaches the other - unis
have to use other senses to find the source of a sound. They quickly learn where sounds that they hear
regularly (doorbell, cookie jar, etc.) are coming from, and many are quite good at using other cues to find
the source of a new noise.
Breeding unilateral Dals does not improve hearing in their puppies, so unis are rarely sold as breeding
prospects. They make excellent family companions. Other than not having directional hearing, unilateral Dals
are typical, normal Dalmatians. They train as easily as other Dals and they are just as loyal, happy, and
playful as their bilateral hearing relatives.