I got out my copy of Sheltie Talk (the "sheltie bible")to see if it would give any insight to the shape of sheltie ears, 'cause I was quite curious about the function after reading the discussion here. Here is what it has to say:
"The correct Sheltie ear is beautiful. It contributes to a soft, intelligent expression and gives an alert look to the entire dog. It is set high, opening forward, semi-erect. The top third of the leather breaks forward with no inclination to turn to the sides. The ear itself is small in relation to the head; the leather strong, yet flexible, and of medium thickness.
Shelties have one of the more functional types of ears of dogdom. The semi-erect ear is useful as well as being aesthetically pleasing. The erect base of the ear works as a scope to trap sounds, providing very acute hearing. The set of the ear allows for mobility, and again, the ability to catch more sound waves. The forward break causes rain to run off, protecting the delicate inner ear without the necessity of pinning the ear (which handicaps the hearing).
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The ear which never needs to be corrected is convenient; and more important, it is correct in a breeding dog. For decades the original working dogs exhibited a fair percentage of individuals with natural semi-erect ears. Can we not expect at least as much from our show dogs who have become so much more standardized in other aspects?
HEREDITY VS. ARTIFICIAL CORRECTION
Unfortunately for the breeder, ears can be difficult. They are influenced not only by heredity, but also by emotional stress, teething, puberty, coat loss, temperature, hormone changes, calcium assimilation, humidity, and age. And to top this off, they rarely inherit as predicted.
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A few breeders feel strongly that ears should never be touched. By showing and eventually breeding dogs that have had their ears fixed, these breeders believe, the occrance of problem ears in the breed will increase, while breeding only those individuals with perfectly natural ears will help to breed out the problem. Unfortunately this is not always feasible. For one reason, dogs from several generations of natural-eared Shelties may show up with problem ears. For another, ears are affected by physiological, environmental, and stress factors. Furthermore, if you have achieved many goals in your breeding program, should you eliminate a dog with incorrect ears and thus lose some more important virtues that you have gained? Of course not. A more realistic position, it seems to me, would be to value and breed for correct ears. Apply corrective measures to those with less than perfect ears, and eliminate from a breeding program any dog that consistently produces very low or very persistent prick ears."
I agree with everything the authors have to say. Taping or glueing sheltie ears does not hurt the dog, and to eliminate a great dog because of ears that didn't come out of mama as perfect just seems... well, not that great of an idea. I do believe that all effort should be made to breed them to a natural, perfect set, but it's just not 100% realistic IMHO.