I spotted this animal in May 2014 in Tusayan Arizona, near the south entrance to Grand Canyon National Park. It is obviously an elk (Cervus canadensis), and it appears to be a female. However, it clearly has a pair of well-developed antlers.
To my knowledge, the reindeer (Rangifer tarandus) is the only cervid species in which females normally grow antlers. I am aware of rare cases of antlered female white-tailed deer (Odocoileus virginanus), but I have not seen anything like this anywhere else, including a fairly extensive search of the internet.
This does not appear to be an example of gynandromorphism, which to my knowledge has not been described in mammals. It might be an example of chimerism or mosaicism, but my guess is that this cow simply has an increased serum testosterone level.
Just seeking thoughts and opinions from the illustrious members of the iNat community regarding this unusual observation. 