Eye color in wild canids is generally light, wolves have eyes with pale
irises. In fact that is part of why the stare of a wolf is unnerving to
humans. Most humans respond to a direct, fixed stare by feeling
threatened and when the iris of an eye is light then it is quite easy
to tell exactly where the light eyed individual is staring. I (BD)
personally beleive this is the major reason that most standards on
European dogs call for a dark eyed dog.|
In domestic dogs there are several genetic factors that influence eye color. Most of the genes are tied into whole body color. If you are not aquainted with dog coat color genetics or terminology you may wish to read our coat color article first.
The coat color genes which influence eye color include merle, spotting (S series), liver dilute (also called brown dilute - the B locus) and blue dilute (the D locus) genes, while others - less well understood - affect only eye color.
Liver dilute (B locus) dogs tend to have yellow eyes while blue dilute (D locus) dogs have bluish, bluish tan or almost silver eyes. Dogs with the merle gene may have eyes of different colors, one blue - one brown or eyes with different colors in them - patches of blue in a brown eye, for example.
Within most breeds there is also a range of intensity of eye color which is independent of the coat color genes. Thus with intense selection one can produce a dark eyed blue dilute greyhound or whippet. However the eyes will be a dark blue brown - not the typical dark brown of the non-diluted dog. It is my feeling - from my breeding program - that the genes that intensify eye color are generally recessive. Crosses of non-dilute dogs with lighter eyes to dogs of similar coat color with darker eyes frequently result in light eyes. The difficulty in studying this is that the coat color genes also influence eye color and so studies of eye color intensity inheritance need to be conducted in lineages in which coat color does not vary. Please contact me, [Bonnie Dalzell] if you have breeding records that would be useful in clarifying this matter that you wish to share [with credit].
The Merle gene is a semi-lethal dominant - dogs with one dose of Merle show the effects of the gene - scattered patches of missing pigment - including on the iris of the eye. They will also show a structural defect of the iris called 'iris coloboma'. Dogs with two doses of the merle gene are frequently deaf and seem to have otherwise reduced vigor.
Dogs that are white because they are extreme white spotted (the S locus) or in which white markings are so extensive on the head that little or no color is found in the area of the eyes often have blue eyes. If the white head markings are assymetrical they may have a blue eye on the side of the head with the most white and a brown eye on the colored side of the head.
In addition there is a blue eye gene that is independent of color. The main breed in which is it seen is the Siberian Huskey.
Terrile Schukraft, a Siberian Huskey breeder who is active in Siberian rescue, would like to add: All blue-eyed dogs do not necessarily have Siberian husky blood in them, although many veterinarians and shelter personnel will identify blue-eyed mixed breeds as Siberian crosses. There are several other breeds that may have blue or split eyes - Dalmatians, collies, Shetland sheepdogs, harlequin Great Danes, Australian shepherds and Australian cattle dogs are examples that come to mind.
[Comment by Bonnie Dalzell:] Many of these dogs are blue eyed because of the dominant merle coat color gene, which may be connected to deafness. The blue-eyed factor in Siberians is NOT connected with deafness, unlike some of the other breeds in which blue eyes may occur. Deaf Siberians are very, very rare. Terrile has never known one in more than 25 years of involvement with Siberians.