Introduction
“The first litter of Great Pyrenees I ever bred produced a dwarf,” recalls Peggy Watson. “I had heard of dwarfs in this breed, but they were surrounded by lots of negative inuendo. Fellow breeders said the dwarf would be in pain, would not survive, and should be euthanized. But I saw a bold and happy puppy that could be a great obedience competitor. So I decided to raise her and train her.” That dwarf was a female that Peggy named Willow. She went on to earn her Companion Dog (CD) obedience title and lived a long and healthy life before she died of suspected cancer unrelated to her dwarfism. “I learned a lot from Willow,” Peggy says. “I was forced to learn a lot about genetics, and it turned into a wonderful education which has made me a better breeder.”
Key Points
- Dwarfism in Great Pyrenees is caused by a single autosomal recessive genetic variant.
- Affected dogs are significantly smaller and may experience hearing loss and dental issues.
- A DNA test is now available to identify clear, carrier, or affected dogs.
- The test helps breeders avoid producing affected puppies while preserving valuable bloodlines.
Challenge Breakdown
Dwarfism in the Great Pyrenees was first described in the early 1990’s. Affected dogs appear normal at birth, but within two weeks are noticeably shorter and smaller than their littermates. While a normal adult Great Pyrenees can stand 25-32″ at the withers and weigh 85-100 pounds, adult dwarfs are only 13-18″ at the withers and weigh 35-50 pounds. Affected dogs often experience hearing loss and require frequent dental cleanings due to crowding of the teeth in their shortened jaw. Both males and females are equally affected. Dwarfism in the Great Pyrenees is not caused by a hormonal imbalance as seen in other dog breeds.
The Breakthrough
Researchers at the University of Minnesota, supported by the AKC Canine Health Foundation (CHF), identified the genetic variant responsible for dwarfism in Great Pyrenees (02400-MOU: Basis of Dwarfism in Great Pyrenees). The condition follows a simple autosomal recessive inheritance pattern, meaning a dog must inherit two copies of the variant to be affected.
The team developed a DNA test that classifies dogs as:
- Clear (no variant),
- Carrier (one copy of the variant)
- Affected (two copies of the variant)
This test empowers breeders to make informed decisions, avoiding affected litters while maintaining genetic diversity. A DNA test for this variant is now available through the University of Minnesota Canine Genetics Lab.
Willow, a Great Pyrenees dwarf, on the right and a normal Great Pyrenees on the left. Photo credit: Peggy Watson.
Impact & Next Steps
This discovery has already changed breeding practices. Instead of eliminating dogs from breeding programs, breeders can now use carriers thoughtfully to preserve genetic material. The test is available through the University of Minnesota Canine Genetics Lab, along with guidance on interpreting results.
Looking ahead, this model of collaboration between breed clubs and research institutions could lead to more breakthroughs for other breeds. It also sets a precedent for how science can support ethical breeding and improve canine health.
