|This polydactyl was found in British Columbia by one of the farrier students at Kwantlen College. Gerard Laverty, the instructor at Kwantlen, sent these images to me, which started my collection. Image © Hoofcare Publishing and Gerard Laverty.|
But when the equivalent of a "double paw" shows up on a giant Shire draft horse, people notice.
The extra hoof (or paw, etc.) is called a "supernumerary digit".
Probably the best and most often quoted opinions on polydactyl horses were in papers published in Scientific American in the 1880s and 1890s by Professor O.C. Marsh of Yale University's natural history department. They are still interesting to read today, and you can find scanned versions of them on the web.
This blog post was inspired by an old post card of what must have been a famous horse in England at one time: Norfolk Spider. Look closely! He was known as the six-footed Shire. Vintage post card is © and courtesy of collector Christine Sutcliffe. (Thank you!).
This horse is the subject of a paper written by three French authors, and published in The Journal of Veterinary Science; the extra digits were surgically removed and the horse went on to develop into a sound adult horse. You can read the full text of Bilateral Polydactyly in a Foal by Carstanjen, Abitbol, and Desbois online.
In evolutionary terms, polydactyls are what some people would call an atavism or a "throwback" to ancestors long ago. There are people who argue about this, of course. A book on my shelf is Hen's Teeth and Horses' Toes by Stephen J. Gould, which you might enjoy; it has some good illustrations of how the polydactyl forms in the limb.
|Look very closely at this radiograph from the Florida Museum of Natural History and the collection of Dr Bruce McFadden, Curator of Vertebrate Paleontology, and author of Fossil Horses: Systematics, Paleobiology and Evolution of the Family Equidae. (Used with permission, © University of Florida and Florida Museum of Natural History)|
Gould updated an old drawing of Dr. Marsh's from Scientific American in the 1800s to demonstrate two of the ways that a horse can grow an extra foot. The first way is for a true second lower limb to form. The second way is for the splint bone to turn into the limb, called the atavistic method. This drawing, from Gould's book, shows you the difference.
Are polydactyl horses truly rare? Unusual, yes. I remember that Dr. Robert Hunt at Hagyard Equine Medical Institute showing photos of polydactyls from his practice in one of his presentations on foals at the AAEP's Foot Seminar in 2009.
While researching this article, I easily found a polydactyl horse for sale in Texas on CraigsList. (Should I have bought him? Is a polydactyl horse more or less valuable than a normal one?)
|Horse described in the French paper, one of the few case studies documenting the condition.|
Todd Neil B. Cats and Commerce. Sci American 237: 100-107 (1977).
Ernest Hemingway was a fan of double-pawed cats and his house today in Key West is filled with the descendants of his original double-pawed cat. About half the cats have double digits. If you've never been there, I recommend it. The cats both run and over-run the place.
My friend Karin has a page on her web site about a polydactyl goat out in New Mexico, complete with radiograph and close-up photographs.
Do you have a favorite polydactyl horse? Usually the extra digit is removed, and you can understand why--poor Norfolk Spider probably hit himself an awful lot.
Some of the better storyteller farriers have told me that they have had been asked to make shoes for the extra toes of polydactyls. I'd like to see a photo of that!
How often do you have to trim the extra hoof, is the next question, of course. Not being weightbearing, it mightn't grow very quickly, but what, if any, effect would feeding a hoof supplement have?
This "extra hoof" seen on a horse treated at Cornell University College of Veterinary Medicine might not even have been noticed if the horse's lower limb hadn't been clipped. (Image © Hoofcare Publishing for Michael Wildenstein)
Norman amassed lifetime track earnings of $6,255 before being exported to New Zealand to stand at stud. He was bought sight unseen, based on his bloodlines. One son won both the Caulfield Cup and the Melbourne Cup. But in general, he was thought to be too small, and his New Zealand owner was going to turn him out with the bush horses when an anonymous buyer made a quite high offer for him.
You can read a great story about Norman Pentaquad in the Australian newspaper, The Age.
Norman moved to Australia and was installed as the new polo stallion at Ellerston, the polo stud farm for Kerry Packer, then Australia's richest human. He went on to become the leading polo sire in the world. In 2010, Norman's offspring represented 11 percent of the horses that played for all nations in the semi finals of the Gold Cup.
I'd love to know how many legs they had between them.
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