This hub was started after I came across this curious vintage photograph of a deer, and my attempt to determine what condition this animal may be suffering from. One obvious feature being that the deer possesses only one antler. It appears that the antler is still in velvet and there is no pedicle or other evidence of the second antler. There is also a prominent growth on the deer's neck.
This picture is from the collection of H E Zimmerman. It shows a deer with one antler and a strange growth. Zimmerman produced pictures of animal curiosities for purchase by the public (in the days before the internet made these things easy to find and disseminate).
The Neck Growth
Protruding growths may occur on deer for a number of reasons, including:
Abcesses: An abscess or cyst can for around an injury and is essentially skin around inflammation and puss. Abscesses often form on the neck as this is where deer can get scratched when moving through underbrush.
Fibromatosis (papilloma virus): This virus generally produces large numbers of smaller growths throughout the body that are sometimes referred to as warts or a fatty tumor.
What do you think the cause is?
What causes a deer to have one antler
If the antler is hard and it is late in the season the buck may have shed one antler and the other is just taking a little longer to drop. However the remaining antler is still in velvet, so this seems unlikely.
If the second antler never forms it may be due to damage to the horn bud while the deer was a fawn so that the horn pedical on that side never developed. More serious damage to the adult animal may have the same result.(Examples: red deer 2012).
One some rare occasions the remaining antler or two merge buds may be repositioned central to provide a "unicorn" appearance.
In rare case the lack of one antler my be congenital (present from birth).