"The explanation of why this happens lies in the physiology of the antler itself. It all begins with testosterone, the hormone produced primarily by the male testes, but which is also found in females (usually at about 1/20th the concentration it is in males). Deer have bony “buttons”, called pedicels, on the frontal bones of their skull. In the spring, a surge of testosterone triggered by increasing daylight levels prompts the pedicels to start developing bony growths. Initially they are soft, covered in blood vessels, nerves and fuzzy skin, referred to as velvet. In late summer a second surge of testosterone causes the bone to harden, the blood vessels to die back, and the velvet to slough off. The male deer rub their antlers against trees and branches to “polish” them, and remove the velvet, and then they use these hardened growths to spar with each other during the rutting season in fall. Early in winter, in the weeks surrounding Christmastime, the testosterone levels start to subside, and a layer forms between the antler and pedicel. Eventually the layer loosens enough that the antler is rubbed off and dropped. In the spring the cycle begins again.
In the case of these unusual does, some trigger such as a hormonal imbalance caused by first pregnancy, tumours, or degeneration or malformation of the reproductive organs or adrenal glands, releases that surge of testosterone that prompts the pedicels to start forming the soft velvet antlers. However, the doe never receives that second surge that results in the velvet sloughing off, or the subsiding of the hormone from this high level that causes the antler to fall off, so she ends up carrying a permanent velvet antler(s). Many such does are reproductively functional and can and do bear young, though others may have malformed reproductive organs. Some of these “does” may actually be hermaphrodites with the female organs dominant, or gyandromorphs (one half of the animal has XY chromosomes, the other XX – that is, one half is male, the other female, sometimes split nice and evenly down the middle like this Rose-breasted Grosbeak). “Does” with polished antlers, where the velvet has fallen off, are more likely hermaphrodites with the male parts emphasized, cryptorchids (males with undescended testicles, “crypto” is Greek for hidden, and “orchid” Greek for testicle), or pseudohermaphrodites that externally resemble females but internally are male."
