Curly Coat and Rex Animals.

Most mammals naturally have straight hair. However a number of relativey common mutations produce hair that is variously described as kinky, curly or rex. In some cases this variation has been used to develop a new breed.

The 'rex' coat appears spontaneously in cat population and sometimes is is selected for and forms the basis of a recognised breed. Rex coats are often light and do not protect cats well from the cold, thus they should be kept indoors. 

Cornish Rex

The Cornish Rex has very short fine hair that is often curled, producing a rippled appearance (see right).

Devon Rex

The Devon Rex dates from 1959, developed from a single curly-haired male kitten.

LaPerm

The LaPerm cat is derived from a spontaneous mutation oberved in some Oregon 'barn cats'. LaPerm kittens are often born bald.

Selkirk Rex Shorthair

A fairly new arrival on the curly-coat scene is the Selkirk Rex, derived from a litter born in 1987. The curly coat is inherited as a dominant gene. This variety is not widely recognised as an official breed. The Selkirk's coat has a loose curl in all hair including whiskers.

Highland cows often develop a distinctly curly appearance, as may other heritage breed ot crosses with wild types such as bison. Long hair is characteristic of many other cattle breeds,but an actual curl may be considered a defect (e.g. in Galloways).

A curly coat gene may be emerging in chinchillas, referred to as curlies or angoras.

A number of dog breeds are known for a curly coat including the Bichon Frise, Curly-Coated Retriever, Irish Water Spaniel and Poodle. The trait may be inherited by cross-breds such as the labradoodle.

Texel

The Texel is a long-haired guinea pig with corkscrew curls.

Curly Horses

There is a gene in American horses that causes long curly or kinky hair, most obvious when they have their longer winter coat. The animals are referred to as "Curly Horses". It has been suggested that many people with allergic responses to horses are able to ride curly horses. The horses curly coat is clearest in their winter when their coat is longer. but the curl is evident all year around in the mane, fetlocks and hair inside the ear.

Manipuri Pony

In India the Manipuri Pony often has a very thick, curly coat. Traditionally used as cavalry mounts they are now popular as Polo ponies.

There are various mutation in mouse population that cause curly coat in the juvenil or adult. for example: rex and stpm.

Mangalitsa

The Mangalitsa pig is a traditional breed that dates from 1833 and is selected to put on thick layers of fat. It has profuse woolly hair that is often curly.

Lincolnshire Curly Coat

The Lincolnshire curly coat is a very rare breed with a particulalry dense and pale coat, resembling a sheeps fleece.

The first animal referred to as "Rex" was a breed of rabbits developed in 1919.  The Rex rabbit has dense, soft fur that is curly in some areas where the hair is long enough.

Rex

Rex rats were developed in 1976. The Rex gene in rats is typically dominant. however the expression fo the curly coat is variable and often much stronger in pups than in adults who may show little or no curl.

Harley & Velveteen

The coat types of Velveteen and Harley also often have a degree of curl. (Shown right, a Harley pup from Paper Heart Rattery)

Many breeds of sheep have a curly fleece (e.g. Shetland),

As with many other species human may have curly hair, and this trait may be under the control of a single gene.

• Searle AG & Jude AC (1956). The 'rex' type of coat in the domestic cat. Journal of Genetics 54, 506-513. [Full Text]