Your Dog’s Coat Color Predicts His Hearing Ability
While most people can accept the fact that a dog's coat color can predict a human being’s emotional response to the dog (click here for an example) it is more difficult for people to accept the fact that fur color can also predict certain aspects of a dog’s temperament and whether or not the dog has certain abilities. This turns out to be true because of a quirk in genetics. It comes about because every so often a gene is found to be linked to other genes. These linkages don't always make sense, but they are sometimes important. Plant geneticists who work on modifying our food plants have often found this to their dismay. For example, the set of genes that makes a tomato more durable, and less likely to be damaged when it is shipped over long distances, also affects the way that the tomato tastes. The sad fact is that the tomatoes that have the gene to keep and ship well have little taste compared to those that are less hardy. Why taste and durability are linked is a mystery, and it is the same kind of mystery that links a dog's coat color to other aspects of his behavior.
One of the most significant things that is associated with coat color in dogs is the fact that the color of your dog’s fur predicts the likelihood that your dog's hearing will be normal or not. Perhaps the most prominent researcher associated with this issue is George Strain of Louisiana State University in Baton Rouge, who has reported data on over 11,000 dogs using the Brainstem Auditory Evoked Response (BAER) test that looks at brain activity caused when sounds are registered by the ears. He has been looking at the factors that predict congenital hearing loss or deafness. A congenital hearing loss is one that is present at birth, although it may take many weeks for it to be recognized by a pup’s breeder or veterinarian. Congenital hearing loss is mostly due to genetic factors, and these are found to be associated with certain coat colors. The coat colors associated with the highest risk are:
piebald (much white with some spotting)
roan (white or gray hairs mixed through the coat)
merle (desaturated colors, especially where blacks become grays or blues)
The classic example of a piebald dog is the Dalmatian. In this breed 22 percent are deaf in one ear, and 8 percent are deaf in both ears, amounting to an amazing 30 percent born with some form of hearing deficit. While all Dalmatians are more or less piebald, in other breeds the white, roan or piebald genes are found in some individuals but not others. In the Bull Terrier, for example, individuals can be either white or can have prominent color patches. Among those Bull Terriers who are white, the rate of congenital deafness is 20 percent, while for those with color patches it is only around 1 percent. In English Cocker Spaniels, the parti-colored dogs often have quite a bit of white on them as opposed to the solid colored dogs which have virtually none. Again this shows up in their hearing ability with the parti-colored dogs being more than twice as likely to be congenitally deaf. The table below gives some numbers from Dr. Strain’s research.
The gene that causes whiteness in a dog’s coat also tends to make it more likely that it will be blue eyed. Thus it seems sensible to expect that blue-eyed Dalmatians would be even more likely to be deaf. This prediction is true and the effect is quite dramatic. Among blue-eyed Dalmatians, 51 percent (or about one out of every two) are deaf in at least one ear. What is worse is the fact that even if the Dalmatian has brown eyes, if one of his parents had blue eyes the chance of being deaf skyrockets. The table below shows the relationship the eye color of the dog’s parents and the rate of deafness in their offspring based on data taken from Dalmatians in the United States.
In certain breeds of dogs, the association between dogs’ coat colors and the likelihood of deafness was noted by early breeders. For example, some Boxer breed clubs report that white Boxers are almost as likely to be congenitally deaf as Dalmatians. For this reason several national Boxer clubs have written into their regulations the requirement that white Boxers are to be culled (the polite word for being killed at birth). The argument is that in puppies it is difficult to sort out the deaf ones from those with normal hearing. Bruce M Cattanach of the MRC Mammalian Genetics Unit Harwell England claims that the rate of deafness in white Boxers is 18%. It is true that detecting deafness in young pups at home is difficult, since the deaf pups cue off the behavior of their littermates. A puppy that does not awaken in response to a loud noise is almost certainly deaf in both ears, but a pup that is deaf in only one ear cannot be detected with any reliability without special testing, such as the BAER test used by Dr. Strain, however such tests are expensive and centers that provide them are few. So Boxer breeders argue that the most efficient means of dealing with the problem is to destroy all of their white pups. This is unfortunate, and unnecessarily cruel, since although 1 in 7 white Boxers may be deaf that still means that 6 out of 7 such dogs will still have normal hearing. Those perfectly sound dogs will end up being killed for no valid reason other than their coat color. Fortunately some White Boxer Rescue groups have sprung up to save some of these potentially fine pets (click here for a link). Until such time that inexpensive and readily available tests for puppy hearing are available that may be the best that we can do.
Reprinted from Canine Corner on Psychology Today with permission.
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