Science or Saint Patrick?

In a manner of speaking, a breed’s silhouette is shorthand for its breed type. Is there any doubt about the breed of the dog below?


Irish Water Spaniel, tail, silhouette, rat tail, whip tail,

If it were possible to show you a line up of AKC sporting breeds by silhouette alone, the Irish Water Spaniel would be instantly recognizable not only because it is the tallest of the AKC’s spaniels, but a “bumpy” outline points to the breed’s famously crisply curled coat. But there’s one more element of that outline that is so important, it’s the source of one of the IWS’s nicknames, “Rat Tail:” A smooth coat on the tail that occurs naturally and require no clippering.

How does nature know to have curls on part of the IWS’s tail, but then taper into a smooth “rat tail” that has no curls at all?

As far as we can tell, the transition from curly to smooth hair on the tail might be the result of a complex interplay of multiple genes that control coat texture. The texture of a dog’s coat is, as we all know, influenced by several genes, and the expression of those genes can vary across different parts of the body on the same dog!  Some speculate that the gene responsible for a curly coat in breeds like Poodles and Portuguese Water Dogs could be expressed in the base of the Irish Water Spaniel’s tail, but as the tail tapers, the influence of this gene could decline and permit other genes that promote smoother hair to dominate, resulting in the “rat tail” or “whip tail”appearance.

To our knowledge, however, the specific genetic mechanism behind why the Irish Water Spaniel’s tail texture is the way it is hasn’t been fully studied, and if someone is the wiser on this point, we’d love to hear from you.
Until something else comes along, one theory is as good as the next, and we have one more to share, this one rooted in legend:
As the story goes, St. Patrick was given lodging for a night by a fisherman who owned a curly haired liver-colored dog especially clever at catching fish. The dog had grown out of his puppy coat, but the poor thing’s tail was still profusely covered with so much hair that it was interfering with his ability to work. The kind St. Patrick said nothing about this during his stay, but when the fisherman woke up the next morning, his Spaniel’s tail was no longer bushy with curls from one end to the other. Instead, it was covered with short curls, but only to a point, the rest of the tail smooth and serving as a rudder in the water, making the dog a better swimmer.

Image: Irish Water Spaniel by LA Shepherd

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