Merle Chihuahuas - The truth and facts about the Merle Chihuahua

The Chihuahua is one of the most popular dog breeds in the UK – the second most popular overall (according to Pets4Homes Statistics), in fact, which means that a lot of UK dog owners share their home with a Chihuahua and there is a significant amount of demand for dogs of the breed among puppy buyers.

The Chihuahua is the world’s smallest dog breed, which helps to contribute to their popularity too. Not only are dogs of the breed undeniably cute and very loving with the people that they trust, but they are also small enough to live happily within even the smallest of homes comfortably, which means they are viable pets for people who could not practically accommodate a larger dog.

Whilst most of us would recognise a Chihuahua if we saw one out and about due to their small size, there can be quite a degree of variance between the appearance of individual dogs of the breed.

Chihuahuas can be found in both long and shorthaired variants, and may also have quite different head shapes too; the round, domed apple shaped Chihuahua head is more common and popular today, but deer-headed Chihuahuas with a less pronounced curve to the head are another alternative.

There are a wide range of different colours accepted within the Chihuahua breed standard too, which offers a lot of options for puppy buyers; but there are also a few so-called rare or unusual colours that some Chihuahua breeders specialise in producing, but which cannot be found within the Chihuahua breed standard.

One of these colours is merle; and merle Chihuahuas are an unusual sight in the UK, and quite distinctive in terms of their coat colour and pattern, which means that they often have a lot of appeal. However, merle Chihuahuas are very controversial, and not widely accepted within the breed as a whole; and for a variety of reasons.

In this article we will look at merle Chihuahuas in more detail, explaining the cause of this colour, its formal status within the breed, and the health implications of breeding merle Chihuahua puppies. Read on to find out everything you need to know about merle Chihuahuas, and the problems that are associated with them.

What is a merle Chihuahua?

A merle Chihuahua is a Chihuahua that displays a specific type of coat colour known as merle, which means that their coats are covered in mottled colour patches over a base colour. The exact shade of merle any dog exhibits can vary, and includes reds, lilacs and blues depending on the base colour of the coat. Blue merles tend to be more common, and subjectively more in demand.

A merle coat may also affect the pigment of the dog’s skin, reflecting the merle pattern above it, and can also mean that the dog in question will have blue eyes, or one blue eye with the other eye being a standard colour.

However, merle is more than a colour; it occurs in Chihuahuas due to a complex combination of inherited genes, which may bring health issues along with them as well as a distinctive, pretty coat. We will cover the potential for merle Chihuahua health issues relating to their colour later on.

Is merle a naturally occurring colour in Chihuahuas?

The Chihuahua dog breed is one of the world’s oldest breeds and as such, it is very well established with a large population of dogs of the breed across the world, and a long recorded history. As a very well-established pedigree dog breed, the appearance norms and desirable traits within the breed are also well established, and reflect the evolution of the breed as a whole.

All pedigree dog breeds have a limited gene pool of dogs within them, and to maintain a breed’s pedigree status relies upon mating only dogs from within the breed. This in turn results in a level of uniformity with only known variables that can develop within individual dogs (such as an array of colour possibilities from those found within the breed), and the only way the traits of a dog of the breed or the breed’s general appearance can change significantly is by means of a naturally occurring genetic mutation, or outcrossing with other breeds of dog.

Merle is not a colour that historically occurred naturally within the Chihuahua dog breed, although it is a standard colour within various other breeds.

How the merle colour was first introduced to the Chihuahua breed is a matter of some debate between breeders and supporters of merle Chihuahuas and those that object to their very existence. Supporters of merle Chihuahuas may claim that the merle colour first appeared in the breed as the result of a naturally occurring genetic mutation, and theoretically this could be true.

However, there is no recorded instance of this happening and no verified information to suggest that the merle gene mutation has presented naturally within the breed, and this viewpoint is widely considered to be unproven or even false.

The other way that merle can be introduced to a breed that does not exhibit the colour naturally is by outcrossing to other dog breeds that do carry the merle gene.

However, regardless of how the first few merle Chihuahuas were actually bred, even if merle appeared naturally in one Chihuahua dog or litter, it would not become established and further replicated within a large number of later dogs of the breed on its own.

All of this together means that merle is not considered to be a natural colour development within the Chihuahua breed, and that it is widely regarded as having been introduced by outcrossing specific Chihuahua breed lines to dogs of other breeds that do carry the merle gene.

What are the accepted Chihuahua colours?

Even though merle colouration is not considered to occur naturally in the Chihuahua dog breed, there are a large number of other colours that do, and that are recognised within the Chihuahua breed standard. The full list of breed standard colours for the Chihuahua within the UK can be found here.

You may notice if you examine the full list in detail that merle is not mentioned anywhere within it.

As well as an extensive list of permissible breed colours that encompass a wide range of patterns and shades, there is also an additional designation given right at the end of the Kennel Club’s colour list: “colour not recognised.”

The “colour not recognised” option can be used to register a Chihuahua with the Kennel Club if they are otherwise eligible (having a traceable pedigree ancestry of registered dogs and no registration restrictions in place) but are not of one of the designated colour options.

It might seem therefore that merle Chihuahuas can be Kennel Club registered as “colour not recognised,” but this is not the case. There is a specific caveat or restriction within the breed designed specifically to address merle Chihuahuas, which we will look at within the next section.

Can merle Chihuahuas be registered with the Kennel Club?

If you have a merle Chihuahua whose parents and lineage were all pedigree Kennel Club registered dogs, it might seem obvious that they too can be registered with the Kennel Club. However, this is not the case; merle is not listed as an acceptable Chihuahua colour, and neither can merles be registered as “colour not recognised.”

From March 2007 onwards, the Kennel Club formally announced a new policy stating that they would no longer offer pedigree registration to merle Chihuahua puppies born on or after 1st March 2007.

This policy was updated in 2009 to add the caveat that no litter or puppy produced from a mating which included a merle parent could be registered either. Another update was added in 2013 too, stating that pups produced from merle-to-merle matings were ineligible for registration too.

Ultimately, this means that there is no above-board way to register a merle Chihuahua with the Kennel Club, and as such they are considered to be ineligible for pedigree registration with no loopholes or exceptions.

What does the Kennel Club say about merle Chihuahuas?

So, why does the Kennel Club take such a strong position on the existence of merle Chihuahuas? There is a lot of controversy surrounding merle Chihuahuas as a whole and various different elements to the debate, which we will cover in more detail later on.

Looking at the Kennel Club’s position specifically, merle is stated as being an “undesirable” colour within the Chihuahua dog breed, and the Kennel Club states that they will not register merle Chihuahuas because this specific colour comes accompanied by an increased risk of impaired hearing and also, vision problems in dogs that inherit it.

What do Chihuahua breed clubs say about merle Chihuahuas?

The Kennel Club works in conjunction with a number of breed-specific organisations and clubs that have developed for many popular dog breeds, and these breed clubs often work closely with the Kennel Club across a number of aspects relating to the breed in question.

This includes things like determining and fine-tuning the breed standard, monitoring breed health, and working to drive improvement within the breed as a whole.

Within the UK, there are several local and national Chihuahua clubs and organisations that are affiliated with the Kennel Club, and the two main clubs with national coverage are the British Chihuahua Club and the Smooth Coat Chihuahua Club respectively.

Breed clubs that are affiliated with the Kennel Club support and help to shape their breed-specific policies, and usually take the same position on breed-specific issues as the Kennel Club does, as is the case for merle Chihuahuas.

The British Chihuahua Club actually compiled a database at one stage of known merle Chihuahua bloodlines in order to help buyers and breeders to avoid inadvertently buying dogs that carried the merle genes, and the Club strongly encourages its members to avoid buying or breeding merle Chihuahuas or carriers of the merle colour.

The Smooth Coat Chihuahua Club’s Code of Ethics does not mention merle Chihuahuas specifically, but breeding them would fall foul of point six of the Club’s code, which states that members “will agree not to breed from any dog or bitch which could be in any way harmful to the dog or the breed.” This is because the merle genes carry the risk of causing health problems in the dogs that inherit them, and also, of being spread ever-more widely across the breed as a whole if this practice continues.

What does it mean if a merle Chihuahua breeder says their dogs are registered pedigrees?

As we have outlined above, the Kennel Club takes a very clear position on merle Chihuahuas and states that they are not eligible for pedigree registration.

This means that if you see an advert for a merle Chihuahua for sale, they should not be advertised or described as being a Kennel Club registered pedigree. However, occasionally merle Chihuahuas are indeed advertised as pedigrees despite this; and it is a good idea for us to explain some of the various reasons why this might be.

First of all, read the wording of the advert in question carefully. Does it actually state that the merle Chihuahua is actually a registered pedigree, or does it say something a little less clear – such as that the dog was bred from “full pedigree parents” or that they have “pedigree lineage.”

These slightly obtuse terms can mislead puppy buyers about the true pedigree status of a puppy, but unless they outright claim that the pup itself is a Kennel Club registered dog, they may not necessarily be false; although to be clear, a legally Kennel Club registered pedigree Chihuahua will not carry the merle gene or be able to produce merle puppies.

If the puppy or dog in question is directly advertised as being a Kennel Club registered pedigree, there are a couple of ways in which a breeder might have gone about fraudulently registering their dog with the Kennel Club to achieve this.

The most likely option is that the breeder registered their merle Chihuahua with the Kennel Club using the “colour not recognised” designation, even though this option does not override the Kennel Club’s blanket ban on merle registration. Ergo, registering a merle Chihuahua in this way is fraudulent.

Another option is that the breeder of the dog in question may have selected one of the named colour options to register their pup, perhaps choosing the colour of one of the parent dogs, or that of the underlying colour that the merle Chihuahua appears to display. Once again, this is fraudulent.

The final option, and one that is something that doesn’t even occur to most prospective puppy buyers, is to find a breed registry other than the Kennel Club that does recognise and register merle Chihuahuas.

Doing this would mean that the breeder can claim some form of pedigree status or registered paperwork for the puppy, but that the organisation that confers it is not the Kennel Club.

Theoretically this is all above board and certainly legal, but it is important to be clear about what breed registry is used. There are a large number of other Kennel Clubs outside of the UK as well as other organisations for dog breed registration that operate internationally, but within the UK and most other countries, the Kennel Club itself is seen as the main or overriding authority for serious breeders, the only registry that really counts.

Few well-regarded international dog breed registries recognise merle Chihuahuas any way – those that don’t include the Fédération Cynologique Internationale, and the Kennel Clubs of Canada, New Zealand, Australia and Germany.

However, the AKC – the American Kennel Club – currently still permits registration of merle Chihuahuas, and so if a merle Chihuahua from the USA was imported to the UK, they might viably come accompanied by formal AKC paperwork. This still doesn’t override the authority of the UK Kennel Club, and so within the UK, AKC pedigree registration that is not transferable (as is the case for a merle Chihuahua) has no real weighting, and dogs that possess it are classed as unregistered in the UK.

Virtually anyone who can build a website and put the work in can set up their own dog breed registry, and invite people to join it and register their dogs (usually for a fee). This means that it is possible for a breeder to pick a registry of unknown origins or no real status and standing and pay them to register their pups, receiving some form of paperwork reflecting this.

This would in turn enable the breeder to advertise their puppy as having some form of registration paperwork with it – but this paperwork will be essentially meaningless outside of that organisation itself.

Can merle Chihuahuas be entered in dog shows?

Formal breed-specific dog shows in the UK are generally organised and operated by the Kennel Club, or affiliated with them. This means that for a dog to be eligible to enter a Kennel Club breed show, they must be registered with the Kennel Club and fulfil all of the other entry criteria too.

This means that merle Chihuahuas cannot enter or compete in Kennel Club dog shows, and if a merle dog was presented on the day, they would be immediately disqualified, and their registration revoked as it should not have been issued in the first place.

However, not all dog shows are Kennel Club operated, or designed to compare different dog breeds. Informal or fun dog shows, and dog shows that don’t fall under the remit of the Kennel Club’s umbrella are generally open to all dogs, and so a merle Chihuahua could compete in shows of this type, assuming they were eligible to compete in general.

How is merle inherited in the Chihuahua dog breed?

As we mentioned earlier on, the merle gene is not one that is considered to have appeared naturally within the Chihuahua breed, so it is worth explaining how the colour can be introduced, and how it is then passed on from dog to dog via their breed line.

To produce a merle dog requires the inheritance of a specific combination of genes that come from the dog’s parentage, and in terms of where these genes come from in the first place, there are two options.

The first is that the merle gene occurs naturally as a genetic mutation, as can and does happen with a wide range of different traits occasionally in different species of animals. However, there is no evidence that this is how the merle gene first appeared within Chihuahua breed lines.

The second option, and the one that is most widely accepted as the way that the merle gene was introduced to the Chihuahua breed is that the merle trait was introduced to Chihuahua bloodlines by outcrossing to an unrelated dog breed that carries the merle gene.

Because of the fact that outcrossing dilutes the bloodline and results in pups that aren’t full pedigrees, tracing the breed or breeds that were used for this accurately in the first instance is almost impossible.

However, once one dog appears in the merle colour or carries the merle gene, the way that this is passed on via different mating matches is much more predictable.

The merle gene is a dominant one, which on its own, means that a puppy only needs to have one merle parent to inherit the merle colour themselves. However, the dominance of the merle gene is incomplete, which means that it does not guarantee a merle puppy will result from breeding from one merle parent.

The merle gene comes in two forms, known as “big M” or just “M,” and “little m” or just “m” respectively.

If a Chihuahua only inherits one copy of the big M gene, they stand a good chance of also inheriting the merle coat, regardless of the colour of their other parent. However, they won’t necessarily be a merle, because the dominance of the merle gene is incomplete. This commonly results in litters produced from one merle and one non-merle dog containing a mixture of merles and non-merles.

If two merle dogs are bred with each other, they pass on two copies of the big M gene to their litter, which results in all of the dogs in the litter being merle. This is called double-merle, and is one way to ensure that an entire litter will display the merle colouration. However, breeding double-merle dogs almost always results in health problems, and so doing this is even more contentious than breeding merle Chihuahuas is already.

If a Chihuahua inherits one or even two copies of the little m gene but don’t inherit a copy of the big M gene at all, they won’t have a merle coat.

How the merle trait expresses itself in dogs that do inherit the colouration can be quite variable too in terms of its eventual presentation, and there are also a number of merle sub-types that can result in only small areas of the coat displaying merle patches, or displaying interesting or unusual colour patterns.

Merle Chihuahua health

Breeding merle Chihuahuas is controversial whichever way you look at it, and the health implications of merle colouration within dogs of the breed is the key point of the debate.

In terms of the health of the Chihuahua breed as a whole, the breed’s lifespan can be quite variable, with averages ranging from 10-18 years. As a long established breed with a large population, Chihuahuas as a whole tend to be robust and healthy despite their small size, but over time, a reasonably long list of health issues that are more common within this breed than others have developed within certain breed lines.

These are hereditary health issues and conformation defects that are passed on from parent dogs to their young, and within the Chihuahua breed specifically, includes conditions like hydrocephalus or a build-up of fluid within the skull, hypoglycaemia, patellar luxation, and epilepsy. You can find out about all of the hereditary health issues that can affect Chihuahuas and learn about conditions that can be DNA screened for prior to breeding within this general guide to Chihuahua health.

When it comes to merle Chihuahuas in particular, they are just as likely to inherit a breed-specific health issue as any other dog of the breed, although the risks can be greatly reduced by choosing a puppy bred from health-tested parents.

However, merle Chihuahuas also have elevated risk factors for some other specific hereditary health issues that are not found within Chihuahuas of other colours, and that directly result from the inheritance of the merle genes.

Merle Chihuahuas have elevated risk factors for both hearing and vision problems, which can be very variable in terms of their presentation. Eye and ear problems that result from heredity of the merle gene are present in affected puppies from birth, and will not improve with age.

Hearing problems relating to the merle gene may affect just one of the dog’s ears or both of them, and may result in either full or partial deafness in the affected ear or ears.

Eyesight problems may range from total blindness to partial blindness, and again, may affect both eyes or just one of them. Poorly formed or abnormally small eyes may result from merle heredity too, although this is less common than general vision problems occurring in normal-looking eyes.

It is very important to note that a merle Chihuahua will not necessarily suffer from either vision or hearing problems, and many merle Chihuahuas suffer from no ill effects as a result of their colour heredity.

However, by buying a merle Chihuahua you are also buying an element of risk, and increasing the chances of choosing a dog with avoidable health issues. Additionally, the risk of health issues accompanying merle in the Chihuahua is considered to be widespread enough and significant enough to threaten the overall condition of the Chihuahua breed as a whole if left unchecked.

As well as the hearing and vision problems that may occur in merle Chihuahuas, the merle colour can also affect the pigmentation of the dog’s skin, which can increase the chances of the dog suffering from sunburn or longer-term threats from sun exposure, like skin cancer.

The additional risks of double merle

Heredity of a single merle gene within the Chihuahua breed comes with a significant risk of accompanying health problems, but also means that puppies bred from just one merle parent may not all be merle themselves.

The only way to guarantee that a mating match between any two Chihuahuas will result in a litter of merles is to breed two merle parent dogs (or dogs that carry the big M gene) with each other. It might seem obvious therefore that if a breeder wishes to specialise in merle Chihuahuas and ergo, maximise the number of puppies that they produce that display a merle coat, that you need to breed two merles together.

However, whilst breeding one merle Chihuahua with a non-merle comes with a significant risk of causing hearing and/or vision problems in their pups, when you breed two merles with each other, health issues are virtually guaranteed to follow.

Breeding merle to merle results in the vast majority of the pups produced from such a mating match inheriting serious problems with both their eyesight and their hearing, and around 25% of double-merle dogs are both fully deaf and fully blind.

The chances of congenital deformities occurring within the eyes as well as vision loss are much higher in double-merle Chihuahuas too, and may cause overly small eyes, or other forms of congenital defects.

Whilst most Chihuahua breeders in the UK frown upon people who deliberately breed merles at all, the practice of breeding double merles is viewed even more poorly, and considered by most to be hugely detrimental to the health and wellbeing of the dogs themselves, and the Chihuahua breed as a whole too.

Understanding the controversies surrounding merle Chihuahuas

If learning that merle Chihuahuas have a greatly increased risk of health problems was news to you, the controversy surrounding the breeding and promotion of dogs of this type might now appear self-evident. The potential for health issues in merle Chihuahuas is of course why most breed registries won’t register merles, and the main point of the objections against this colour within the breed at all.

However, there are several other elements that also factor into the merle Chihuahua controversy, which are not as immediately obvious to most dog lovers, so in this section we’ll cover all of the key points of contention in the merle Chihuahua debate.

Merle Chihuahuas and health problems

As we covered in more detail above, the merle gene within the Chihuahua dog breed comes along with an increased risk of congenital health issues in Chihuahuas that inherit it. Whilst by no means all merle Chihuahuas will have health issues and many of those that do will only have minor issues, merle Chihuahuas have a much higher risk of being born deaf, blind or both, or having partial hearing and/or eyesight in one or both eyes or ears.

Merle colouration may also make dogs more sensitive to the sun, particularly in the case of shorthaired or smooth coated Chihuahuas, who have less fur to protect them.

The double merle risk

Producing merle puppies when only one parent is a merle dog is likely, but not guaranteed. To guarantee a merle litter, two merle parent dogs must be bred; this results in double-merle pups. However, double-merle dogs also have much higher risk factors for significant congenital defects of the eyes and ears, and around 25% of double merle dogs are both deaf and blind.

They also have higher chances of being born with deformed eyes and ears.

Even healthy merle Chihuahuas are not without controversy

Some merle Chihuahuas are healthy with no hearing or vision problems at all, but even if a breeder manages to produce a heathy merle litter, doing so is never without risks. There is no guaranteed way to breed healthy merles without the risk of health issues, so breeding any merle litter means that there is a reasonable chance that one or more of the dogs in the litter will have health problems of some type.

This is why the practice of breeding merles full stop – even individual healthy dogs – is controversial, because even if one pup is healthy, other pups within their litter or later pups bred as a result of demand for merles may not be.

This means that by breeding or buying merle Chihuahuas, you are actively contributing to the development of potential health problems within dogs of the breed, even if an unhealthy dog never passes through your hands.

Dilution of the breed’s core traits

Deliberate changes are only formally made to a dog breed (or its breed standard, which committed breeders try to adhere to and match as closely as possible) and endorsed on a large scale if these changes advance and improve the breed, and are in the best interests of both the breed as a whole and the individual dogs within it.

The practice of changing a breed by means of breeding for a certain physical trait, or particularly, by introducing a new trait or gene from outside when this is not undertaken for reasons of improvement and advancement is viewed very poorly by the Kennel Club and breed organisations.

Even though merle Chihuahuas are not widely spread throughout the breed and cannot be used within pedigree breeding programmes, the more merle Chihuahuas that are bred, the greater the chances are of this trait spreading and becoming a problem within the wider Chihuahua population as a whole.

From a breed policy point of view, this is a very bad thing. When the trait in question not only falls outside of the breed standard but may also be harmful to the dogs that possess it, there is a lot of backlash against merle Chihuahuas as a result of their potential impacts on the breed as a whole.

The rarity of merle Chihuahuas

Merle Chihuahuas are often advertised as being rare, unusual or in short supply, which helps to add prestige to their ownership and keep demand high. Breeders who sell merle Chihuahuas often describe this rarity as a unique selling point or advantage, without ensuring that prospective buyers understand why such dogs are rare, and the downsides of owning and breeding them.

Pricing merle Chihuahuas

As you might expect when a dog is sold as something rare or special, merle Chihuahuas often change hands for prices much higher than those commanded for an equivalent dog of the breed in a standard colour.

This is considered by many standard Chihuahua breeders and breed advocates to be immoral and unethical.

Ensuring that puppy buyers get the big picture

Finally, many people who spot a merle Chihuahua for sale and that fall for their charms have no idea that the colour is associated with health issues and wider implications for the breed as a whole. As mentioned, breeders who are trying to sell controversial dogs or those with health issues are unlikely to ensure that prospective puppy buyers fully understand what they are getting into, particularly if they’re asking high sale prices for their dogs.

Whilst the onus is of course on puppy buyers to research their purchase and ensure they make a wise choice, dog breeders also have a moral responsibility to their dogs and prospective buyers to provide all of the information necessary to make an informed choice. All too often, this fails to happen when it comes to merle Chihuahuas.

Are merle Chihuahuas rare?

Merle Chihuahuas are often described in adverts as being rare, one-of-a-kind, or otherwise in short supply, which many sellers use very effectively to create and increase demand for their dogs for sale.

But how rare are merle Chihuahuas really? Let’s look at the figures.

Pets4Homes is the UK’s biggest and best pet classifieds and animal advice website, and by collating information from adverts placed here on the site, we can develop a general snapshot of the state of the wider market.

At the time of writing (February 2019) there were a total of 552 Chihuahuas and Chihuahua litters for sale, of all types advertised on Pets4Homes. Just seven of these were merle dogs or litters, which represents just over 1%, or a little over one in a hundred dogs of the breed.

If this approximate percentage is a true representation of the wider state of the market, it is certainly fair to say that merle Chihuahuas are rare and uncommon. This is a good thing from the point of view of the breed as a whole and the breed’s policies, but is often portrayed as a good thing for rath