Dog Discoveries

Dog Word of the Day: Rat Tail in Dogs


A rat tail in dogs usually refers to the typical appearance of the tail seen in dogs suffering from low thyroid levels, but how and why do dogs with low thyroid levels develop such a tail? How is rat tail in dogs treated? Is rat tail in dogs something that can be prevented from occurring in the first place? These are all important questions. Fortunately, low thyroid levels in dogs can be corrected with the use of medications. While the term rat tail in dogs usually refers to the tail seen in dogs who are hypothyroid, interestingly, some dog breeds come naturally equipped with a rat tail and this tail is mentioned in the breed standard.

Tail typical of canine hypothyroidism
Rat tail in dog

Rat Tail in Dogs with Hypothyroidism

Hypothyroidism is the medical term used to depict low thyroid levels. In dogs, low thyroid levels are common; whereas, in cats, the condition of high thyroid levels (hyperthyroidism) is more common.

Among the variety of symptoms low thyroid levels in dogs may cause (lethargy, weight gain, behavior changes, hair loss, cold intolerance), hypothyroidism is also known for causing a variety of skin and coat changes.

Affected dogs may develop a dull coat, changes in hair texture, dry skin, black spots, darkening of the skin, greasy skin, skin infections and hair loss. Clipped hair may never grow back. The hair loss often presents in typical patterns, affecting mostly the trunk on both sides, symetrically.

Another classical sign of hypotyroidism in dogs is  the so-called “rat tail.” Dogs presenting with a rat tail typically exhibit hair loss from the last few inches of the tail.

Fortunately, once low thyroid levels in dogs are diagnosed and the dog is given the proper medication,  he or she should show signs of improvement within a few weeks. It can take though a little longer for the hair coat to improve.

The Rat Tail Spaniel

The Irish water spaniel is a dog breed known for having a rat tail.

According to the American Kennel Club, the Irish water spaniel boasts a “body covered with a dense, crisply curled liver colored coat contrasted by a smooth face and a smooth “rat” tail.”

In more detail, the tail presents as thick at the root where it is covered with short curls for two to three inches which are then replaced by smooth hair with the tail tapering to a fine point.

Photo Credits:

Wikimedia: Alopecia on the tail typical of canine hypothyroidism,  Creative Commons Attribution-Share Alike 3.0 Unported license.


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