Whether Two Merle Collies Should Be Bred Together
Seeing two blue merle Collies together can make a litter look striking, but coat color is not the only thing to consider. Breeding two merles can produce puppies with a higher risk of hearing and vision problems. This guide explains why, what responsible breeders test, and how to assess a pairing without mistaking a puppy’s appearance for proof of its genetic status.
Why breeding two merle Collies raises concern
How merle inheritance works
Merle is a coat pattern associated with a change in the PMEL gene. In a simplified model, a dog with one merle copy may have a mottled or patchy coat, while a dog that inherits a merle copy from each parent may have a mostly white coat with smaller areas of pigment. These dogs are often called double merles.
When both parents carry one copy of the merle variant, each puppy has a separate chance of inheriting no copy, one copy, or two copies. Under that simplified model, the expected proportions are about one-quarter with no merle copy, one-half with one copy, and one-quarter with two copies. Those are probabilities across a litter, not a promise about the exact number or outcome of puppies. A small litter may not match the expected proportions.
Merle inheritance can be more complicated than the simple model suggests. Variations in the merle gene can affect how clearly the pattern shows, and a dog may carry a merle variant that is difficult to recognize by looking at its coat. That is one reason responsible breeding decisions should be based on reliable genetic information, not just a visual guess. For background on coat appearance, see What a Blue Merle Collie Looks Like and Whether a Blue Merle Collie Is Rare.
Why double merle puppies may have sensory problems
The concern is not simply that a double merle puppy may be mostly white. The combination of merle variants can be associated with a lack of pigment in parts of the inner ear and eye. In some dogs, this can result in deafness, vision impairment, or structural eye problems. The extent varies: a puppy may have hearing or vision affected on one side, on both sides, or not show an obvious problem.
That uncertainty can be difficult for a family choosing a puppy. A white-looking puppy may hear well, while a puppy with more visible color may still have a health issue. Coat pattern cannot confirm whether a dog can hear or see normally, and an informal response to clapping or calling is not a substitute for appropriate veterinary assessment.
It is also important not to treat risk as certainty. Not every dog with two merle copies will have the same outcome, and appearance alone cannot predict an individual puppy’s abilities. But a possible healthy outcome does not make a merle-to-merle pairing a responsible gamble. Avoiding a preventable risk is the safer breeding choice. For a closer look at the range of outcomes, read Whether a Double Merle Collie Is Deaf or Blind.
What responsible breeding decisions look like
Choose a non-merle mate for a merle Collie
The straightforward way to avoid producing double merle puppies is not to breed a merle Collie to another merle Collie. A merle dog paired with a dog that is genetically confirmed not to carry a merle variant cannot pass a second merle copy to a puppy. This does not remove every inherited health risk from a litter, but it avoids the specific risk created by inheriting merle from both parents.
The phrase “not merle” should not rest on a quick look at the coat. A dog may have a subtle or hidden pattern, or its appearance may be confusing because of other coat-color genes. A breeder considering a pairing should confirm each dog’s status through an appropriate genetic test and discuss the result with a veterinarian or qualified canine genetics professional if the report is unclear.
A responsible breeder should also consider temperament, health history, structure, and the overall suitability of the pairing—not just color. Prospective buyers can ask how the breeder distinguishes a visually non-merle dog from one that has been genetically tested. Useful broader context appears in The Four Colors a Collie Comes In and The Collie Was a Scottish Droving Dog Before It Was a Show Dog.
Ask for records rather than reassurance
If a breeder says two merle Collies are safe to pair because they have produced healthy puppies before, ask to see the parents’ genetic results and the puppies’ relevant health assessments. A previous litter cannot guarantee the outcome of a future one. Each puppy inherits a new combination of genes, so past results do not remove the underlying concern.
Ask what testing was done, which dog was tested, and whether the records identify the tested dog clearly. A screenshot or a verbal statement may not provide enough context to confirm the result. A breeder who takes health planning seriously should be willing to explain the documents and answer reasonable questions without making you feel difficult for asking.
A genetic panel can address more than merle status, but its coverage varies. It should not be treated as a universal guarantee that a puppy will never develop a health problem. To understand what a broader panel may include, see What the Collie DNA Health Panel Covers and The Three Genetic Tests a Collie Breeder Owes You.
How to assess a litter and its puppies
Separate coat color from health assessment
A puppy’s coat can be a clue to ask more questions, but it is not a diagnosis. A mostly white puppy is not automatically a double merle, and a colored puppy is not automatically free of merle-related risk. White markings can result from different genetic factors, so it is important not to assume that all white Collies have the same cause or health outlook. For that distinction, see Whether a White Collie Is the Same as a Double Merle.
For an individual puppy, ask what genetic testing has been done and whether hearing and eye evaluations are appropriate. A veterinarian can help determine what examination is suitable. If a puppy has a suspected hearing problem, a formal hearing assessment such as a BAER test may provide information that observation at home cannot. An eye examination by a veterinary professional can assess concerns that are not obvious from a puppy’s coat.
Screening does not make a risky pairing advisable after the fact. It can help identify a puppy’s needs and guide care, but the more responsible approach is to avoid creating a preventable risk in the first place. If a litter already exists, the practical priority is honest disclosure, appropriate evaluation, and thoughtful placement—not blame directed at the puppies.
Questions to ask before choosing a puppy
A careful conversation with a breeder can tell you a great deal. Ask whether both parents were tested for merle status, whether the results are available for review, and what steps the breeder takes to assess puppies’ hearing and eyes. You can also ask how the breeder will support a puppy who needs accommodations or follow-up care.
| Question | Why it matters |
|---|---|
| Were both parents genetically tested for merle status? | Appearance can miss subtle or hidden merle patterns. |
| Can I review the test records for the actual parents? | Records help connect a result to the dog being bred. |
| Have the puppies had appropriate hearing or eye assessments? | Coat color alone cannot establish normal hearing or vision. |
| What health information will come with the puppy? | Clear records help your veterinarian plan care. |
| What support is available if a puppy needs extra help? | Responsible breeders plan for each puppy, not only the easiest placements. |
A breeder who answers plainly and provides relevant records is more reassuring than one who dismisses the questions or relies on “we’ve never had a problem.” You can also look at how openly a breeder shares health information more generally in Whether a Collie Breeder Should Publish Results.
If you are preparing for a puppy, a basic supplies list can reduce last-minute stress. Some owners compare routine items through retailers such as Chewy, while also following the breeder’s recommendations for food and equipment. Keep the focus on practical needs—safe bedding, a suitable crate, food, and grooming tools—rather than buying specialized products before you know what the puppy requires.
What to do if a breeder proposes a merle-to-merle mating
Treat pressure to decide quickly as a warning sign
You do not need to reserve a puppy simply because a breeder says the pairing is unusual, beautiful, or expected to produce a popular color. If records are missing, the breeder will not explain the genetic risk, or you are urged to ignore questions about hearing and vision, pause the conversation. A responsible decision should leave room for you to understand the facts.
If you have already paid a deposit or signed an agreement, review the written terms and ask the breeder to clarify them. Do not assume that a health guarantee covers every inherited condition or that a verbal promise changes the contract. For help thinking through purchase documents, see What a Collie Breeder's Contract Covers.
You can also discuss the proposed pairing with your veterinarian or a veterinary genetic specialist. That conversation is especially useful if a test result uses unfamiliar terminology, if a parent’s pattern is subtle, or if the breeder offers conflicting explanations. The goal is not to diagnose a breeding dog from a distance; it is to make sure the decision is grounded in evidence rather than reassurance.
If a double merle puppy is already in the litter
A puppy should not be rejected or treated as less worthy because it may be deaf or have limited vision. Many dogs with sensory impairments can learn routines, bond closely with their families, and enjoy a good quality of life when their needs are understood. The important steps are honest disclosure, appropriate veterinary assessment, and a home prepared to communicate and manage the puppy safely.
For a deaf puppy, families may need to use visual cues, vibration, consistent routines, and secure barriers instead of relying on spoken recall. For a puppy with impaired vision, a predictable home layout, clear pathways, and careful supervision around stairs or unfamiliar spaces can help. The exact accommodations depend on the puppy’s abilities, which is why individualized assessment matters.
Ask the breeder what support and records will accompany the puppy, and make a veterinary appointment soon after bringing the puppy home. If you are comparing breeders, a willingness to discuss testing, results, and puppy welfare is a meaningful part of the decision. For related screening questions, see Whether a Collie Litter Should Be Screened for Deafness.
Disclaimer
This article is for general informational purposes only and does not constitute professional advice. Laws, prices and regulations vary by location and change over time. Consult a qualified professional for guidance on your specific situation.
