by Charlie MacInnes 

All standards for breeds which have normal muzzle length (like their wolf ancestors) call for a scissors bite.  That occurs when the lower incisors sweep upward close behind the upper incisors as the jaw closes.  The reasons for desiring a scissors bite are neither clear nor simple.

My thinking on this was much influenced when, in 1972, I bought my first Cardigan bitch.  I visited a hill farm in Wales, the home of Eddie Young of Rhiwelli.  The bitch I eventually bought was in a large pen with about fifteen other dogs of six breeds.  There were three fresh, skinned sheep heads that had been thrown into the pen that day.  I believe that was part of the old way of feeding dogs, letting them have parts of carcasses that were not wanted for human consumption, plus left over food, such as large bones with some meat still attached. A scissors bite would be the most efficient for stripping meat scraps off bones. More significant, perhaps, is that the teeth of a level bite wear faster, because the cutting edges rub directly together when the dog is working on a bone such as a sheep skull.  That would mean that dogs with level bites would die at younger ages, due to faster wear of the cutting teeth.  In addition, even in today’s world of more gentle diets, dogs with level bites tend to lose incisors as they age.  That must have been worse in olden times.  Since a lot of effort and emotion goes into the training and maintenance of a good herder (or any other working companion), early death would be a clear disadvantage, especially if the dog was used in competition, as the great ones do their best work when older and experienced. 

An undershot bite would not enable the dog to strip bones very well, so maybe such a dog would be less thrifty, again a disadvantage.  An overshot bite would clearly be a disadvantage to eating such Spartan rations.  Then, when the bite is far removed from scissors, the adult canines may dig into the roof of the mouth.   It would have been expensive to feed a pup until that problem became obvious.

All that sounds plausible, doesn’t it?  I am sure there is a good deal of truth in it.  The trouble is that there is no way of proving it conclusively, and there are other modifying factors. 

One idea is that a scissors bite was the most effective for delivering strong nips to the heels of herded livestock, or intruders to the homestead.  It certainly is true that the nips that a few of my dogs delver to the calves of strangers who come in my gate are bruises, without holes from the canines.  However, would a cow get as “gentle” treatment as that, and would it respond any differently to a level or undershot bite?  When I watch Sue Mesa’s competitive herding dogs respond to the command “bite him” the dogs certainly take a good mouthful, including using the canines, but having the sense or the training not to draw blood or rip the skin. 

Another viewpoint is that the teeth of horses and cattle are very important to survival.  Since these animals were essential to the very survival of humans, there is a huge lore about their structure and health.  Selection of just the right individuals for future breeding stock was fundamental to prosperity.   Farmers and landowners who grew up steeped in the proper knowledge and rules would have been very particular about getting it right.   Perhaps, even though there is no proof of the superiority of the scissors bite, it was chosen because to do so followed the rules of the more important farm animals.

A countervailing view is that dogs did not live nearly as long, on average, before vaccines for distemper, hepatitis and other diseases became available, and that did not happen until the 1940s or later.  Thus, too much wear may not have been so important, if the average dog died of disease before it was old enough to be hampered by bad teeth.  Should we be so worried about the correct scissors bite, now that modern dog foods avoid excessive wear of the incisors?

Much is made in some breeds about all the premolars being present, yet, as far as we know, premolars have very little function.  Wildlife biologists who want to know the age of a study animal will pull a premolar for microscopic examination, on the theory that loss of one of the 8 premolars will not reduce the animal’s probability of survival.   Judges from continental Europe are rigorously trained to check that no teeth are missing.  This seems to descend from the idea that a dog worth showing should be perfect in every respect.

In summary, there is good reason to favor the scissors bite, both as being more functional at any given moment, and as important to longer survival of the individual dog.


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