Australian Shepherd: Size, Merle, Lifespan and Genetics
Canada's No. 6 breed is a herding dog that got its name in the American West, known for merle coats, blue eyes and natural bobtails. Here's its size, the genes behind its colours, eyes and tail, the MDR1 drug-sensitivity variant, and what to know about lifespan.
By PuppyGenes · How we research and write our guides
The Australian Shepherd is a medium-sized herding dog that, despite its name, came to North America with Basque shepherds and got its name in the western United States. It was Canada's sixth most popular breed in 2025. It's known for merle coats, blue or odd-coloured eyes and, in some dogs, a natural bobtail, and each has been linked to a specific gene. About three in ten Australian Shepherds in one study carried a variant of the MDR1 gene that can make dogs dangerously sensitive to some common drugs, which is worth discussing with your vet.
At a glance
| Trait | Australian Shepherd |
|---|---|
| Size | Males about 51 to 58 cm; females somewhat smaller. The AKC gives about 23 to 29.5 kg for males and 18 to 25 kg for females |
| Coat | Medium texture, straight to slightly wavy and of moderate length, with an undercoat that varies with the climate |
| Colours | Blue merle, red merle, black or red, each with or without white markings and tan points |
| CKC group | Herding |
| Origin | Dogs of Basque shepherds that became known as Australian Shepherds in the western U.S. |
| Life expectancy | 12 to 15 years, according to the AKC |
| Popularity | No. 6 in Canada |
Not actually Australian
The CKC's breed page traces the breed to dogs that worked with Basque shepherds in Spain and Andorra. When Basque herders followed sheep farming to Australia and later to the western U.S., their dogs went along and became known in America as Australian Shepherds. The breed has been popular with North American livestock people for more than a century.
Today it's Canada's sixth most popular breed, and it's fifth in the CKC zone covering Nova Scotia and Newfoundland and Labrador, as our list of the most popular dog breeds in Canada shows.
Blue merle, red merle, black and red
Four base colours, each with or without white and tan, come from a few genes:
| Colour | Base pigment | Merle? |
|---|---|---|
| Black | Black | No |
| Red | Brown, from two brown copies of the TYRP1 gene | No |
| Blue merle | Black | Yes |
| Red merle | Brown | Yes |
Merle is a marbled pattern of diluted patches, caused by a short DNA insertion in the PMEL gene that a 2006 study identified. One copy gives a merle coat. On a black base it's called blue merle, and on a brown base red merle. What breeders call "red" in this breed is a brown pigment, and brown coats come from two brown copies of the TYRP1 gene, as a 2002 study of brown dogs showed. Tan points come from the agouti gene, and white markings from white-spotting genes.
Two merle parents carry a real risk: about one puppy in four inherits two copies, and research has found these double merles are much more likely to be deaf. Our guide to merle dogs explains double merle and why some merle carriers look solid.
Blue eyes
Australian Shepherds often have blue or partly blue eyes, by two routes. Merle can lighten the eyes when diluted patches reach them. And non-merle Aussies can have blue eyes too: a 2018 study of more than 3,000 dogs linked blue eyes mainly in Siberian Huskies to a DNA duplication near the ALX4 gene, and also found it associated with blue eyes in non-merle Australian Shepherds. Our guide to blue eyes in dogs covers both routes.
The natural bobtail
Some Australian Shepherds are born with naturally short tails. In the Australian Shepherd and many, but not all, other naturally bobtailed breeds, the short tail comes from a single change in the T gene, which the OMIA genetics database lists for the Australian Shepherd among other breeds. A 2001 study of bob-tailed dogs found the change acts dominantly, so one copy shortens the tail, and that puppies with two copies don't survive to birth. A 2009 study of 23 breeds with natural bobtails found the change in 17 of them, found no dogs with two copies, and found 29% smaller litters in the Swedish Vallhund when both parents were short-tailed.
The MDR1 drug-sensitivity variant
A variant of the MDR1 gene can make dogs dangerously sensitive to some common drugs. A 2004 study traced it to breeds from the working collie lineage and measured how common it was:
- Australian Shepherds: of 178 dogs, 29.8% carried one copy and 1.7% carried two, so about three in ten carried it.
- Miniature Australian Shepherds: of 56 dogs, 44.6% carried one copy and 3.6% carried two.
If you have an Aussie or an Aussie mix, ask your vet about MDR1 before it's treated with drugs known to be affected. The PuppyGenes report doesn't include genetic disease or health screening, so it isn't a substitute for an MDR1 test.
Lifespan
The American Kennel Club lists a life expectancy of 12 to 15 years. As a medium-sized breed, the Aussie sits in the middle of the size and lifespan pattern seen across dogs, which our guide to why big dogs have shorter lifespans explains.
Temperament and energy
The CKC describes the Australian Shepherd as eager to please, loyal and responsive, quick to learn and easy to train, and sometimes reserved with strangers. It was bred to work livestock, so it thrives on activity and needs regular exercise and challenging tasks. Breed is a loose guide to any one dog, though: a 2022 study of more than 18,000 dogs found breed explains only about 9% of behavioural differences between individual dogs.
Aussie mixes and DNA tests
The PuppyGenes breed ancestry section estimates a dog's breed mix as percentages, and the coat colour section reports merle where the sample supports interpretation, though in some samples merle can't be determined; if merle matters for breeding, ask about the parents. If you're weighing a test, our guides to whether dog DNA tests are legit and dog DNA testing in Canada cover what to check before you buy.
Frequently asked questions
- How big do Australian Shepherds get?
- Males usually stand about 51 to 58 cm at the shoulder, according to the CKC, and females are somewhat smaller. The AKC gives weights of about 23 to 29.5 kg for males and 18 to 25 kg for females.
- How long do Australian Shepherds live?
- The American Kennel Club lists a life expectancy of 12 to 15 years. Individual dogs vary with their health, size and care.
- What colours do Australian Shepherds come in?
- Blue merle, red merle, black and red, each with or without white markings and tan points. Merle is the marbled pattern, and red is a brown pigment from two brown copies of the TYRP1 gene.
- Why do some Australian Shepherds have no tail?
- Some are born with a natural bobtail from a dominant change in the T gene. One copy shortens the tail; puppies with two copies don't survive to birth.
- What is MDR1 in Australian Shepherds?
- A gene variant that can make dogs dangerously sensitive to some common drugs. In one study, about three in ten Australian Shepherds carried it, so ask your vet about testing.
- Are Australian Shepherds from Australia?
- No. According to the CKC, the breed began with dogs of Basque shepherds in Spain and Andorra, which travelled with them to Australia and then to the western United States, where they became known as Australian Shepherds.
From general to personal
See how this applies to your dog specifically.
Our at-home Complete Dog DNA Test adds your dog's own results to these tips across six report sections: breed ancestry, coat colour, physical appearance, temperament and size predictions, genetic diversity and oral microbiome. The report does not include genetic disease or health screening.