It should be noted that here in Australia the following wording was added to The Chihuahua Standard - Smooth and Long Coat by the Australian National Kennel Control in May 2005 under Coat Colour: Any colour permissible or mixture of colours except Merle of any combination. Hence in Australia we cannot register or show any dog displaying the merle pattern.

Chihuahuas carrying the merle gene cannot be registered nor shown in Germany, England, Wales, Scotland, and Canada effective January 2008. It was voted upon by the Chihuahua Club of America in Oct 2007 to disqualify the showing of merle Chi's; this decision was sadly overturned by the membership. I think I can safely say that most of the world wide Chihuahua Community were incredulous, to say the least, at this turn of events. Mexico, the country of origin of our Chihuahuas, does not allow the registration or showing of Merle Chihuahuas.

The Merle gene is a dilution gene that creates a specific coat pattern it is NOT a colour. It lightens whatever coat colour would otherwise have been. The dilution is not spread evenly over the coat. It leaves patches of undiluted colour scattered over the dog's body. The dilution works primarily on the black pigment in the coat, so any tan or fawn colour stays even. Black includes liver or chocolate as both of these colours are dilutes of black.

The merle pattern is completely separate from that of sabling, spotting or brindling and may or may not include patches of white. Merle is NOT a mutation. It is a dominant coat pattern (MM or Mm).

For a dog to be merle, at least one parent MUST be carrying the merle gene. This also means that this gene cannot lie dormant for generations and suddenly reappear as some overseas breeders have claimed.

Mrs Hilary Harmer, Aztec Chihuahuas (UK), Mrs Thelma Gray, Rozavel Chihuahuas, Marjorie Fearfield M.B.E. (Bowerhinton), founder of the British Chihuahua Club in 1949, Mrs Margaret Rider, Rowley Chihuahuas, Miss D Russell-Allen, Dalhabboch Chihuahuas, and Lady Margaret Drummond-Hay, Seggieden Chihuahuas to name just a few stalwarts of our breed in the very early days made NO mention of the merle pattern in Chihuahuas. This suggests only one thing - the only way the merle pattern was introduced into our breed was to breed to a dog of another breed that carries the merle gene. Thus the progeny are mixed breed dogs. To register them as purebreds is both unethical and illegal.

Most Chihuahua lovers say that Mrs Hilary Harmer, of the famous Aztec Chihuahua prefix was one of the original "guru's" of our beloved breed, it is very interesting to note that as early as 1968 she made the following reference to the merle gene in her book "Dogs and How To Breed Them" (page 9) under the heading of "Lethal Genes".

The attached articles should be read to add to your knowledge on this subject

These are some very good links that explain how the merle gene affects canines:

Reprinted here with the permission of the original author,
Vivien Cotton - Joviva Chihuahuas