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Within the Maine Coon breed we talk about the clones or the clones percentage. But what is meant by this exactly?

When talking about the clones, we are talking about the 17 descendants of Tanstaafl Polly Adeline or Heidi Ho (Polly) and Heidi Ho Sonkey Bill (Sonkey). The reason that they were given the name "clones" is because the kittens looked exactly the same. Just as if they were copies of each other, painted with a different color. These comments were also made when the breeder presented her first litter at a show. Because of this the label "the clones" has remained.
Both parents got champion titles added to their names and their first growing kittens did very well on show also. This made the clones in the early 1980's very popular. The similar look of the kittens was very desirable at the time, because the predictability of future good showresults made them very attractive for other breeders. Sonkey and Polly together had 7 litters. From these litters, 17 kittens were used into breedingprograms. Below you can see a screenshot from Pawpeds of the clones. The first colums shows that many of them have indeed obtained their showtitles.

The 17 clones themselves also got offspring; a total of 226 kittens and 1,459 grandchildren. Not all of these (grand) children were used into breeding, but a lot did. The lines were very popular because they performed well on show. You understand that with this enormously high breeding production in combination with their popularity, it result into a major impact on the Maine Coon of today, which is about 40 years later.

Many of these 17 clone brothers and sisters can still be found in the pedigree of the Maine Coon of today. Today a Maine Coon has a clones percentage of 35% on average. This means that 35% of the pedigree of this cat consists of the clones from 40 years ago. Sometimes the clones can be found more than 70 times in the family tree.

Sonkey - the father of the clones


First we take a look at the father of the clones, Heidi Ho Sonkey Bill (Sonkey). Sonkey was an F3 male (3rd generation foundation). His pedigree consists of 100% of the Top 2 most common foundation cats, Andy and Bridget. Two children of Andy and Bridget were mated (Henri Sayward and Heather, brother and sister). A daughter of that, Henrietta, is again paired with her father (Henri Sayward). Sonkey was born as a result. Sonkey's father is also his grandfather and Sonkey his grandmother is also his aunt. Andy and Bridget are both his grandfather and grandmother on father's side, and twice his great-grandfather and great-grandmother on mother's side. Sonkey therefore has an extremely high total inbreeding coefficient of 37.5%.

Sonkey had 42 offspring (including the 17 clones). Sonkey also became a grandfather of 404 grandchildren, of which 225 related to the clones. The other 179 grandchildren of Sonkey are from female partners other then Polly. Those 179 offspring obviously have a clones percentage of 0%.

In his pedigree you can see the double ancestors in the same color. This is a pedigree that most breeders will avoid at all times. Still, Sonkey and his clones are found in almost all of the Maine Coon family trees today. 

Heidi Ho Sonkey Bill
Polly - the mother of the clones


Polly's (Tanstaafl Polly Adeline or Heidi Ho) pedigree consists of fewer inbreeding matings than those of her partner Sonkey. Her total inbreeding percentage is 7.81%. Half of her mother's line consists of Andy and Bridget. But Polly's pedigree also contains the three other foundation cats, which together with Andy and Bridget form the top 5 most common foundation cats. Polly's pedigree consists of Dauphin de France or Tati-Tan for 31.2%.Thanks to Polly, Dauphin is number 3 of the top 5 most common foundation Maine Coons.











The 17 clones

Let's take a closer look at the pedigree of these 17 clones; the kittens of Sonkey and Polly.

Their inbreeding percentage over 4 generations is 5.47%. And the total inbreeding% is 9.38%. The top 5 foundation cats is 91%. You can see by this high percentage that a high clones percentage automatically means a high top 5 percentage. In fact, this means that the top 5 percentage is AT LEAST 91% of the clones percentage. Example: when a Maine Coon has a clone percentage of 40%, the top 5 percentage has to be at least 36,4%. The other way around you can't predict the height of the clones by looking at the top 5. The top 5 had offspring creating different lines then the clones. In theory a Maine Coon can have a top 5 % of 70% and a clone percentage of 0%. These lines weren't used as much as the lines of the clones and therefor those lines are very rare or maybe even died out.

The most counted ancestors of the clones (also called top 5 foundation):

Number 1 and 2: Bridget Katt of Heidi Ho (Andy) and Andy Katt of Heidi Ho (Bridget) are counted evenly in the pedigree and together are 64,1% of the pedigree of the clones

Number 3: Dauphin de France of Tati-Tan is 15,6% of the pedigree. The total of the top 3 together is 79,7%.

Number 4: Tatiana of Tati-Tan is 7,8% of the pedigree of the clones.

Number 5: Smokie Joe of Whittemore is good for 3,52% of the pedigree of the clones. The total of this top 5 is 91%.

Now you understand where the top 5 foundation cats came from. The use of the clones in many breedingprograms created this top 5. You will also understand why it is not just a top 5, but the top 3 and top 2 is mentioned separately. There is a big difference between the 32% of Andy and the 3,52% of Smokie Joe.

clone stamboom.PNG

Below you can see the photos of some of the clones.

SGC Heidi Ho Molly B. of Tanstaafl
clonen diverse jaren.PNG
The impact of the clones today 

Because the clones were born about 40 years ago, it is not something that every current breeder takes into account. The clones are mostly no longer visible in the last 10 generations. Many breeders are therefore not aware of their impact today. The volunteers of Pawpeds have therefore developed the possibility to calculate the clones percentage for each Maine Coon. This way you can see exactly what percent of your cat's ancestors consists of the clones. To see this percentage, click on the "clone" link at the top of the family tree in Pawpeds.

The Swedish breeder Malin Sundqvist has done research in

the Pawpeds database to see the development of the clones

percentages in 5 specific years. In the graph you can see her result.

The average clones % in 1980 was 2.9% (logical since only a few

clones were born in 1980). Clones percentage grows as time goes

on. In 2018 the average clones percentage is 34% of all registered

Maine Coons. The 2nd column compared to the 3rd column is also

interesting. The 2nd column shows the average inbreeding

percentage of only the last 5 generations (line breeding). It is surprising that despite the fact that practically no line breeding was applied in 2018 (there are no or few double ancestors in the last 5 generations), the total inbreeding percentage (3rd column) has risen. There is therefore a clear relationship between the height of the clones percentage and the height of the total inbreeding percentage. This can be explained by the fact that a Maine Coon with a 34% clones percentage consists of at least 34% of the same ancestors. There may be some variation within the clones. For example, a Maine Coon that has 34% clones but that consists 100% of the "Heidi Ho Aurora or MtKittery" clone will have a higher inbreeding level than a Maine Coon with 34% clones where this percentage is more evenly distributed among the various clones.

In addition, a Maine Coon with a high clones percentage automatically also has a high foundation top 5 percentage (the 5 most common foundation cats). Only a small percentage of ancestors then remain where the unrelated ancestors and unrelated genes must come from.

In the 80s there were many other lines that were used for breeding apart from the clones. Unfortunately, the clones were so popular in that period that many breeders sooner or later added an offspring of the clones to his or her own breeding program. Old lines with a low percentage of clones can therefore hardly be found today. The lines that do have a low clones percentage are mainly the lines to which a New Foundation Maine Coon has been added. By adding new blood to the breeding program, the clones percentage can be drastically reduced.

Why low clones is more important than low inbreeding or a low top 5

You may understand that if the current population has an average percentage in clones of 35% or higher, this will result in severe narrowing of the gene pool. The necessity is therefore high to breed with Maine Coons that are as unrelated to these 17 clones as possible.

The clones, top 5 and inbreeding percentages are linked to each other. The higher and higher the clones percentages gets, the more Maine Coons get related to each other. As explained above, the clones have the top 5 most common ancestors behind. This top 5 will increase together with the increasing clones percentage. The average top 5 foundation percentage is 70% nowadays.

With an increasingly higher clones percentage, the average inbreeding percentage of the population also rises due to their connection to each other. It will then become increasingly difficult for a breeder to make low inbreeding combinations in the future, because there are fewer and fewer unrelated lines to be found. The table shown and discussed above shows this trend well. 

The lines that are still low in the clones are often mixed too quickly and too much with lines that are high in the clones. This is often understandable from the point of view of that one breeder. A breeder wants to achieve his own breeding goal and compensate for the weaker points of the line. After all, there is a lot more selection in the population of high clones lines to find the perfect cat to complement your breeding program. However, the total population of the breed would be better served by pairing lines with low clones to other unrelated low clones lines. This increases the amount of cats that are low in the clones. This helps the total population to a higher genetic variation. In the future this will result in more opportunities of continuing to make low inbreeding combinations.

Low clones - breedingprogram

In the Netherlands there are very few outcross breeders (who breed with a clones percentage below 20%). Of the hundreds (400-500) Maine Coon breeders in the Netherlands, probably around 3-5% focus on outcross. The Netherlands is no exception here, because this trend is visible worldwide.

With this article I hope to create more awareness about the clones among breeders, so that more breeders want to make this a priority in their breeding program. Not everyone can or want to work with outcross. It can't even be possible for every breeder to work with outcross, because unfortunately there are too few outcross Maine Coons available due to these trends. But every breeder can take the clones into account in his or her breeding program. Even if it is only a few percent per mating or for a new cat that you buy, every small step helps the breed to a lower clones percentage and higher genetic variation.

You can find more interesting articles about the clones here:

- Interview with the breeder of the clones, Beth Hicks

- Article about "The Clones" on

- Article about the clones and foundation cats and their history

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