The Australian shepherd is a medium sized breed of solid build. They can be anywhere from 30–65 pounds and anywhere from 17–26 inches in height. The ASCA standard calls for the Australian shepherd to stand between 18–23 inches at the withers, females being 18–21 inches and males measuring 20–23 inches, however, quality is not to be sacrificed in favor of size.
Aussie colors are black, red (sometimes called liver), blue merle (marbled black, white and gray), and red merle (marbled red, white and buff), each of these colors may also have copper (tan) points or white markings in various combination on the face, chest, and legs. A black or red dog with copper and white trim is called tricolor or tri, a black or red dog with white trim but no copper is called bicolor or bi. White, rather than pigment, on or around the ears is an indicator of increased risk for white-related deafness. Excessive white on the face and ears can place an individual dog at greater risk for sunburn and subsequent skin cancer.
The wide variation of color combinations comes from the interaction between the a color allele, which is either black (B) dominant or red (b) recessive, and the dominant merle allele (M). Together, these provide four coat-color aspects that can appear in any combination:
- Black, with tan points, white markings, or both on the face, collar, legs, chest, underbelly. Solid black dogs are equally desirable as ones with tan or white.
- Red (Liver) with or without tan points or white markings on the face, collar, legs, chest, underbelly. Either white or tan points are required. Solid Red dogs are equally desirable as ones with tan or white.
- Blue Merle (a mottled patchwork of gray and black) with or without tan points or white markings on the face, collar, legs, chest, underbelly. Neither white nor tan points are required. Solid Merle dogs are equally desirable as ones with tan or white.
- Red Merle (a mottled patchwork of cream and liver red) with or without tan points or white markings on the face, collar, legs, chest, underbelly. Neither white nor tan points are required. Solid Merle dogs are equally desirable as ones with tan or white.
The merle allele, which produces a mingled or patchwork combination of dark and light areas, is the coat pattern most commonly associated with the breed. This merle (M) is dominant so that unaffected dogs (Mm) show the pigmentation pattern; however, when two merles are bred, there is a statistical risk that 75% of the offspring will end up with the two copies of the merle gene (homozygous). These dogs usually have a mostly white coat and blue irises, and are often deaf, blind, or both. In this case, the deafness and blindness are linked to having two copies of the merle gene, which disrupts pigmentation and produces these health defects.
All black and blue merle dogs have black noses, eye rims, and lips. All red and red merle dogs have liver or brown noses, eye rims, and lips.Red merle with copper points and one brown eye and one blue eye. Blue merle with copper points with blue eyes
There is also great variety in the Aussie's eye color. An early nickname for the breed was "ghost-eye dog". Aussie eyes may be any shade of brown, or blue; they may have two different colored eyes, or even have bicolored or "split eyes" (for example, a half-brown, half-blue eye), which appear to be linked to the merle coloration. Merled eyes occur as well, where one color is mixed in and swirled with another. Any combination of eye color is acceptable in the breed standard, so long as the eyes are healthy. In general, however, black Aussies (self, bi-color or tri-color) tend to have brown eyes, while red (self, bi-color or tri-color) Aussies tend to have amber eyes, though these Aussies may also carry the blue-eyed gene.
A hallmark of the breed, some Aussies are born with naturally bobbed tails (NBT). Others have full long tails, and others with natural partial bobs, where the tail is midlength and appears stubby. Breeders have historically docked the tails when the puppies are born. Even without a tail, the wagging movement still occurs as the dog wiggles or shakes their hind end. In the United States and Canada the standard calls for a natural bob or docked tail not to exceed four inches as a defining characteristic, however some long tailed examples have been successfully shown and been given recognition despite having a longer tail. Any natural tail length is permitted when showing in Europe, where docking has been banned in some countries.