Understanding Deafness in Dalmatians...
With their patchy coat and their familiar image atop fire trucks, Dalmatians are among the most well known of dogs. Less well known is the fact that they can suffer from a genetic defect that causes them to spend their lives in silence or with impaired hearing.
In fact, Dalmatians have the highest prevalence of deafness of any breed. About 30 percent lose their hearing because of a genetic defect.
Every animal has two genes for each of his traits, one inherited from the mother and one from the father. Deafness can be associated with a single gene or multiple genes. In this specific deafness, multiple genes are thought to be involved. This means that dogs can be completely deaf or only deaf in one ear. And, deaf parents can have offspring that are not deaf if all the associated genes are not inherited by the offspring. However, breeding deaf dogs, even those with deafness only in one ear, is not recommended.
Inside a dog’s ear, there is an organ that converts sound waves into electrical impulses that travel to the brain and are processed as sound. In this type of genetic defect, the organ responsible for the conversion starts to degenerate in the first few weeks of life.
Some puppies are affected in only one ear and some are affected in both. Since normal puppy ear canals do not open until they are 6 to 14 days of age, a puppy with this genetic defect never hears out of one or both ears.
Testing for deafness can be difficult. If you try to use a loud sound, such as clapping, a puppy that is deaf in only one ear will still respond to the noise. And some puppies may seem to hear because they adapt or respond to other cues that they may see. The most accurate way to measure hearing ability is an electrical test called “BAER” test, which gauges the brain’s ability to detect sound. BAER stands for Brainstem Auditory Evoked Response.
Deaf animals may be difficult to arouse from sleep, may be more aggressive than normal littermates and may be very vocal. They are difficult to train, but with patience and proper effort, deaf dogs can make good pets.
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.
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 -the 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 a unilateral hearing is that the unilaterally hearing dog does not have a 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.