Merle is a colour combination in dogsâ€™ coats. It is a solid
base color (usually red/brown or black) with lighter blue/gray
or reddish patches, which gives a mottled or uneven speckled
effect. Although most breeds that can have merle coats also
typically have white markings (such as around the neck, under
the belly, and so on), and often tan points (typically between
the white and the darker parts of the coat), these are separate
colors from the merle; some dogs do appear completely merled
with no white or tan markings. Merle is a distinguishing marking
of several breeds, particularly the Australian Shepherd, and
appears in others such as German Coolies in Australia, the
Shetland Sheepdog, various Collies, the Welsh Corgi (Cardigan),
the Pyrenean Shepherd, the Catahoula Leopard Dog, the Koolie,
the Old English Sheepdog and others. Merle is actually a
heterozygote of an incomplete dominance gene. If two such dogs
are mated, on the average one quarter of the puppies will be
double merles and some percentage of