Dr. Tom on supernumerary appendages

My young son harvested this jake Rio turkey in western Kansas. The bird is normal except for the extra appendage or toe just inside the feather line of its leg. Both of us are curious as to what we are seeing for sure. Any information to shed some light on the subject would much appreciated.

Chris Rhoades, via email

Thank you for contacting Turkey Country and Dr. Tom with your question and for sending the photo of the young tom your son harvested. Since retiring as a regional biologist with NWTF, I have been answering inquiries as “Dr. Tom.” First of all, congratulations to your son on his success this spring! The jake he took is certainly a very unusual specimen. Abnormalities or malformations occur in every species but they are quite rare. Most folks are familiar with house cats that have six toes instead of the normal number. Over the years, I have seen newly hatched snakes with two heads and fish with extra appendages. Though I have handled thousands of wild turkeys while live-trapping and examining harvested gobblers, I have never encountered an abnormality like this. Often animals that have malformed appendages or other abnormalities have limited survival. In this case, the abnormality was not serious enough to limit survival.

Looking carefully at the photograph you sent, you might notice swelling at the base of the extra appendage. Without an x-ray or examination of the skeletal system, I cannot be sure, but the swelling may be a heel joint or the center of an extra foot that failed to develop to maturity. The extra appendage therefore is either an extra lower leg or an additional set of toes. In either case, the extra appendage is either the result of a very rare hereditary issue, or something that occurred in embryonic development while the bird was growing in the egg. 

An extra appendage is referred to as a supernumerary appendage (more appendages than normal). Looking through some of the literature on deformities in birds, I found documentation of a green-winged teal with extra wings, a mourning dove with an additional partially developed foot and a few references of this condition in domestic chickens. Neither of us is likely to ever see another example of this type of abnormality in a wild turkey as it is extremely rare. Thanks for sharing the photo!

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