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The Curly Hair and Feather Gene in Domestic Animals

Theophanes is a New-England-based blogger, traveler, writer, photographer, sculptor, and lover of cats.

Frillback Pigeon

Frillback Pigeon

Curly Fur, Hair, and Feathers

Throughout the domesticated animal kingdom, curly hair and feathers have been prized in various breeds for their beauty and uniqueness. Humans have purposely bred these animals for all sorts of reasons. It may come as a surprise that the genes responsible for these mutations often behave the same despite being in vastly different species, suggesting they might be the same genes responsible in some cases.

In any event, the curly hair may have given some of these animals an edge while it may have done the exact opposite for others. Still, they remain enormously popular, and it doesn't look like that is ever going to stop! So come with me on a journey through history and meet some of the fascinating characters that make up this story.

Angora Goat

Angora Goat

Fiber Animals

Curly coats are pretty much what makes a sheep a sheep, but did you know their curly coats are what makes their wool so much better to use than just an animal with a lot of straight fur? Indeed, the tighter the curls on a fiber animal's hair the easier it is to spin into yarn or thread (and the stronger that yarn or thread will be.) That is why sheep were the perfect animal for this when we started domesticating them somewhere between 9,000 and 11,000 years ago. Their fiber is called wool, short and simple.

Though we may have started with sheep other fiber animals followed. Ancient Turkey is largely credited for the development of the Angora goat, an ancient breed that predates the Bible in historical references. They have long curly coats which are shorn just like a sheep's to create a type of fiber called mohair.

Alpacas also have naturally curly hair, though it is very dense and you might not realize it until you're petting one. The waves can be seen when the hair is inspected in individual strands and is called crimp. The higher crimp the wool has the better quality it is. They are a South American animal and as such the records of their domestication have been sparse but we do know that they were being kept in captivity for meat and possibly wool for at least 6,000 years. The fiber from an alpaca is called Alpaca Wool and is softer than sheep wool but still very warm.

The First Curly Exhibition Animals: Frillback Pigeons

Most people are a bit surprised to hear that pigeons were among some of the earliest domesticated animals and were likely the first birds we bothered to bring into captivity. They were ideal for captivity due to their prolific nature, raising a brood of chicks one after another sometimes all year long. They were kept initially as meat animals, their chicks being raised for squab, but eventually they would find work becoming carrier pigeons while still others were bred merely for their beauty.

Probably the oldest mutation seen in these new fancy pigeons was one that caused the feathers to be curled. These curly birds were called Frillbacks and were first mentioned in text in 1640, although they likely were bred far longer than that. The gene that caused their feathers to curl was a dominant one, meaning that any curly pigeon bred back to a regular pigeon would produce some curly offspring. This gene showed up in the larger meat birds and this continued to be a trend even though their new beauty came at a cost.

These birds were no longer able to fly normally and could not escape predators well. They also could not slick off water when it rained like their smooth counterparts, nor could they retain as much heat since their feathers were no longer sitting over their skin. This resulted in a somewhat more fragile animal, one who probably couldn't exist outside of the protection of captivity.


Frizzled Poultry

Just like pigeons chickens and geese also have a curly feather gene called frizzled. In chickens the frizzle gene does not constitute its own separate breed, instead it's something that appears in any breed. This is easy to accomplish as it's a dominant gene and chicks from any pairing could end up frizzled. In geese, they do consider the frizzled variety their own breed—called Sebastopol geese.

Texel Guinea Pig

Texel Guinea Pig

Guinea Pigs

Guinea Pigs are another ancient oddity. Unlike most of the small pets we have today they were domesticated at least 5,000 years ago as meat animals in the Andes mountains. They are still raised in the region to be the main ingredient in a dish called cui. Here in the States, however, they are far more common as pets and exhibition animals.

Though they come in several different varieties the long curly-coated Texels currently reign supreme in the show circuit today. They were created in the 1980s in England by crossing the short curly-coated Rex guinea pigs with other longer haired breeds. Rex guinea pigs have short dense hair that resembles a wool-bearing animal.

Curly Swine

There are only two breeds of pigs known to have curly hair, the now-extinct Lincolnshire Curly-Coated Pig, and the new boar on the block, the Mangalica. The Mangalica was developed in Hungary by crossing curly-haired pigs with wild boars in the 19th century. They were prized for their fast-growing, marbled meat, and ability to live through and raise piglets even in the harshest of winters due to their thick coats. Recently they have been imported to the United States and are a very popular new variety of pig for enthusiasts. I am unaware of any attempts to use their fur for anything but they sure look like they could be used for fiber arts!

Curly swine

Curly swine

Curly Horses

Curly horses have been around for thousands of years, likely as random mutations throughout the centuries. They've been seen painted on cave walls, Asian paintings as far back as 161 AD, and Native Americans maintain that curly horses led the charge into the Battle of Little Bighorn. Today they are their own breed, of sorts, called at different times Curlies, Curly Horses, Bashkir Curlies, American Bashkir Curlies, and North American Curlies. Their ancestry is a contentious issue among fanciers partly due to the fact this is a dominant gene making it super easy to add this characteristic to other breeds, therefore muddling their history.

This is why this 'breed' of horse has no specific size, weight, body type, or appearance, other than their characteristic curly coats. They are said to be particularly cold-hardy because of this unique feature and regardless of where they come from they have a vibrant following in the United States and beyond.

Curly horse

Curly horse

Curly-Coated Dogs

There are many breeds of dogs with wavy or finely curled coats but we're going to focus on the kinkiest ones. The most popular curly-coated dog today is probably the poodle, likely followed by other favorites like the Curly-Coated Retriever, the Bedlington Terrier, the Irish Water Spaniel, and the Portuguese Water Dog. These are by far not the only curly-coated dogs; in fact, curly coats can be seen on everything from the tiny Pumi to the regal Komodor. Similarly, these curly coats vary a lot in texture, density, and amount of curl.

Some dogs like the Puli and the Komodor are known for their unique haircuts which result from taking their poodle-like curly hair and manually dividing it into ropes until they develop a mop of dreadlocks. This process can take up to three years of daily fussing. This is probably why no one does this with poodles even though they can have the same effect! It is the curls in their hair that allows for the dreadlocks to form so easily. Straight haired dogs are more likely to form matts rather than dreads.

Curly-Coated Cats

There are currently four breeds of curly-coated cats strutting their stuff in the show ring today. There are two short-haired varieties, the Cornish Rex and Devon Rex; and two long-haired varieties, the Selkirk Rex and the LaPerm.

Cornish Rex

The Cornish Rex has short intensely soft hair that is caused by a lack of guard hairs leaving nothing but a down coat. This lack of guard hairs makes for their spectacularly soft feel but leaves them vulnerable to the cold. They make a popular pet because they don't shed and have wonderful playful temperaments. They were first developed as a breed when a litter of barn cats had a few kittens with curly coats on a farm in Cornwall England in 1950. The kittens were cross-bred to other cats to create the breed.

Devon Rex

Devon Rex are much like the Cornish except they do have guard hairs which gives their coat a course feel. They are a separate mutation but also were discovered in England like the Cornish. Their ancestry goes back to a kitten born in 1960 to a feral cat that was sired by a curly-coated tom that was seen in the area but never captured. Curiously, even though the two breeds came from the same area and time they appear to have a completely different genetic lineage. Early breedings showed that a Cornish bred to a Devon only resulted in straight-haired kittens!


The LaPerm is a long-haired, super soft, curly-coated cat. The first was found in a feral population in Oregon in 1982. They were also a simple dominant gene and continue to be cross-bred with other breeds to increase genetic diversity in the breed.

Selkirk Rex

The Selkirk Rex is a long-haired curly-coated cat that was discovered in a shelter in Montana in 1987. Like the LaPerm, this cat seemed to have a dominant form of curly hair and was bred back to very chunky breeds to create a larger more robust longhaired curly-coated cat.

Curly Cows

Salers cows, originating in France, are a dual purpose breed which sports a curly coat. They're also great in winter and are known for a high fat content in their milk.

Curly cow

Curly cow

Rex Rats

Curly-coated rats have been bred in the laboratory and in the fancy since at least 1976. There is one common gene—the dominant rex gene—that shows up frequently in the hobby but there are five and possibly more genes that cause rexing in rats that have been documented in laboratory settings. They are respectively the common Re gene most hobbyists work with and Cu1, Cu2, (k), Sh, and cw (cowlick) genes seen in laboratories.

The dominant rex gene should not be bred together as two rex rats often produce something called a Double Rex which is a rat lacking in guard hairs, often bald in large patches. Double Rexes, when bred together, will eventually produce completely bald babies, just like the frizzling in poultry breeds.

A long wavy haired rat was found in a pet store in 2002 and the Harley breed was born from there. It appears this gene is recessive and causes a long coat and a lack of guard hairs leaving a whispy coat. The breed is very new however and is displaying some concerning health problems, including protein sensitivities, mastitis, aggressive temperament in some of the males, and skin problems. It has a ways to go before it's a stable breed.

Rex rat - baby

Rex rat - baby

Curly Mice

Rex mice are much like rex rats. They're common amongst fanciers and have been successfully crossed with Satins to produce Satin Rexes.

Rex Mouse

Rex Mouse

Rex Rabbit

Rex Rabbit

Curly Rabbits

Curly-coated rabbits are a bit of an anomaly. Rex rabbits, bred for their meat and pelts, are well known. They have extremely soft dense fur that doesn't appear overall curly but sometimes is. Longer haired rabbits sometimes exhibit curly hair—I have found some angoras have distinct lazy waves. There is at least one breeder in the US trying to reinvent the extinct Astrex Rabbit which is a rabbit of medium coat length that is quite curly.

At one point various breeders have tried to introduce the curls of the rex rabbit into the angora rabbit breed to create a stronger fiber. Sadly this resulted in "possum" rabbits who matted badly even with daily care. This endeavor resulted in failure because of this and no one has picked it up since.


Curly Chinchillas

This is one of the newest curly mutations of anything out there. The curly chinchillas, called Locken chinchillas, were first imported into the U.S. from Germany in 2007. This is a dominant mutation so they can be bred with regular straight-haired chinchillas and still produce curly babies which is great for increasing the gene pool. Lockens bred to other Lockens seem to produce even curlier babies but no baldness like in rats and chickens. Even more interesting this gene seems somehow linked to the black color gene. Only chinchillas who are black or have black in their background show up curly!

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2016 Theophanes Avery


Taralynn Timer on April 29, 2020:

Same!! my project is about genes & heredity. I knew about lots of these such as cattle swine & equine as well as dogs & cats( I live on a farm soo) But the other animals were interesting & cool.

Dianne Fitzmaurice on September 23, 2019:

I started reading to find out more about the genetics of curls so your article title is deceptive. While it is very interesting given the variety you missed 2 very significant fiber animals that have this feature . Suri alpacas and suri llamas. The suris are quite distict and would I really would like to know more about the genetics involved other than dominance. Specifically whether there is a distinction genetically beeeteen lock structure and curls.

Ratgirl. on December 31, 2016:

Wow, the pigs and horses are pretty amazing looking things. But that chinchilla!!! Thats gorgeous, but i wonder, is it as soft as the normal chins? They Probably wouldnt be good candidates for fur coats then, at least!