In the September of 1877, a drover cum dog dealer, James Whitburn, was scheduled to leave for New Zealand with a consignment of breeding sheep and a coffle of rough coated herding dogs which were destined to be the ancestors of that rather nebulous type of sheep herding dog, the Smithfield Collie. Just prior to his departure he received a letter of advice from his cousin, John Logan of Lanarkshire which read: above all I urge you to beware of white collies. I have heard they do not inspire respect from sheep, but this is not the reason for the wisdom I offer you. I have found. Them recalcitrant, difficult to train and of a stubborn, difficult nature Two I have known bred near Penicuik, have a reputation for savagery to their shepherds
Logan wrote these words some thirty years before Punnet and Pease and Punnet and Bateson expanded the science of genetics and published their Scientific papers concerned with the subject of incomplete dominance, so it is highly unlikely that Logan would have realised that the white collies of which he wrote, were in all probability the result of a union between two Merle coloured collies and hence were almost certainly physically, not mentally defective.
Merle coloured collies are not a whit inferior to their black and white or brown and white litter mates, though David Hancock, The world’s largest breeder of collie-bred lurchers, suggests that if a litter of puppies is subjected to some stress dystokia, chilling etc, Merle puppies are more likely to suffer than their normal coloured litter mates. However problems only occur when Merle coloured dogs are mated together. A Merle mated to a non-merle animal will produce a litter of roughly 50% Merle and 50% non-Merle progeny with a low incidence of hereditary defects. However, when Merle animals are mated together one quarter of the progeny are white and usually have defective hearing and eyesight. Hence it is inadvisable to mate two Merle coloured collies, lest a quarter of their offspring are defective.
However, the breeding of Merle coloured collies is thwart with danger. David Hancock, who has bred many Merle coloured puppies, states that while it is usual to be able to detect Merle coloured puppies at birth many puppies lose this curious Merle dappling at birth and resemble solid or non Merle animals after a week or so. Yet genetically these animals are Merles and should not be mated to another Merle.
Serious breeders of Merle coloured dogs and colour breeding is a great skill—label obvious Merle coloured animals OVERT-Merles and Merles, which do not manifest obvious Merle colourations, COVERT-Merles.
Merle colouration is not confined to border collies, However Merle Dachshunds- known as dapples-are both attractive and popular, though the coloration is considered undesirable in Great Danes.
Merle specimens are not found in the KC registered Bearded collies though this should not automatically suggest that Merle coloured Working Bearded collies are tainted with Border collie blood. When Olive Wilson decided to revive the show bred Beardie, She merely used animals, which were not merle as her initial stock. It is likely that Merle coloured Bearded collies have always existed. The late Tom Muirhead had Merle coloured bearded collies in his kennels just prior to his death. His Merle stud dog was full coated and displayed no Border collie influence and supposedly come from Gwyn Jones of Powys. Yet Jones` stock was descended from Merle coloured Bearded collies Tom had sent south in 1966-67.
A long and circuitous article perhaps, but it does perhaps explain Logan’s antipathy to white collies which may well have been bred from covert Merle collies and hence may well have had defective vision and hearing. Such animals approached in a heavy-handed manner may well have been frightened and retaliated. Their impaired hearing and eyesight might also have explained why Logan considered them difficult to train.