Thursday, November 29, 2007

Things I Never Knew: Dew Claws

I learned something yesterday- what they say about learning something every day is true- dew claws are not a random occurance in dogs. Rear dews, especially, are specifically bred into some dog breeds, and discouraged in others. A dew claws are defined as "superflous claw inside the hind leg just above the foot" by Charles Inglee (see Dog Dew Claws). These claws are sort of a vestigal thumb, or innermost 5th digit on domestic canines. One of the only articles I could find about the genetic causes of rear and double dew claws in certain breeds, from 1983, was off limits to me (and us, dear reader), as I do not have a subscription to the online version of the Journal of Heredity. The next best thing is this blog about Icelandic Sheepdogs, a breed which requires dews on all four legs and doesn't fault rear double dews. Interesting reading if you know the difference between penetrance and expressivity (I don't).

So, which dogs are supposed to have rear dew claws? Some breeds have been bred to specifically have no dew claws for so long that they never have dews. Others have been bred for so long that not having two extra rear thumbs would seen an oddity. Who knew!?
According to the following French website and my own research, the following Breeds should have rear dews, rear double dews, etc.

Rear Dews Required
Berger des Pyrenees

Rear Dews Allowed
Portueguese Sheepdog
Saint Bernard
Treeing Tennessee Brindle

Rear Dews Not Allowed
American Eskimo
Giant Schnauzer (should be removed)
Flat-Coated Retriever
Neopolitan Mastiff (must be removed)
Nova Scotia Duck Tolling Retriever
Chesapeake Bay Retriever
Soft Coated Wheaten Terrier (presence should be penalized)
Low Chen (should be removed)

Rear Double Dews Required
Briard
Great Pyrenees
Beauceron

Rear Double Dews Allowed
Pyreneen Mastiff (Double Dews preferred)
Anatolian Shepherd
Icelandic Sheepdog

Front and Rear Double Dews Required
Catalonian Sheep Dog

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