Field Notes: Antlered Does
During the 2002 deer-hunting season, Tom Schneider of Willmar shot a white-tailed deer with a polished 13-point rack. Nothing strange about that. But something was unusual: The deer, by all appearances, was a doe, with female genitalia, an udder, and teats.
Why do some does grow antlers? How common are they? Are they really does? These are some of the questions hunters ask as deer such as Schneider's trophy focus attention on these unusual creatures. With the exception of caribou, females of the deer family do not normally grow antlers. Yet reports of antlered female white-tailed, black-tailed, and mule deer go back more than a century. Most of these have velvet-covered pedicels or small spikes with some branching, and can produce fawns. The scientific literature also contains reports of a few deer that appeared to be females except they had hard, polished antlers.
The physiological process of antler development helps to explain how antlers can develop in does. White-tailed deer antlers are made of bone. They grow from pedicels ("buttons") on the skull. Annual antler growth begins in mid-March to April, triggered by the interaction of increasing daylight, testosterone, and the hormone prolactin. During early development, the antlers are composed of blood vessels, nerves, and a hairy skin called velvet.
In August or September, a second surge of testosterone, the most important stimulant to antler growth, is released, causing the velvet to die and the bone to harden. The deer eventually rubs the velvet off, and the antlers become polished. By late December or early January, the supply of testosterone declines and a separation layer forms between the antler and pedicel. The antlers drop off shortly thereafter. In March or April, the process to begins again.
Researchers have noted that females can have a testosterone surge caused by a hormone imbalance, first pregnancy, tumors, or degenerative conditions of the ovaries or adrenal glands. This single surge can cause the growth of antlers in velvet.
Indeed, researchers estimate one in every 1,000 to 6,000 white-tailed females produces antlers. In Pennsylvania, researchers reported one antlered doe per 3,500 antlered deer. A 1985 study in Alberta, Canada, documented that eight of 517 adult does had antlers (about 1 in 64). The reasons for the high number of antlered females in this region: perhaps because every harvested deer was examined, or there may be a genetic predisposition for female antler growth.
Postmortem examination by researchers around the country indicates that does with antlers in velvet tend to be reproductively functional, or to have complete but malformed reproductive tracts, or to be true hermaphrodites in which the ovaries are more developed than the testes.
What about "does" with polished antlers? For the velvet to die and the antlers to become polished bone, a second surge of testosterone is necessary. Reproductively functional females will not get the second surge. Deer that appear to be does with polished antlers are almost always reproductively malformed males, which will have a second testosterone surge that causes the antler velvet to shed. Postmortem research on these deer shows most are cryptorchids, hermaphrodites with male organs predominant, or pseudohermaphrodites (animals with external female genitalia but internal male reproductive organs). Because its antlers were large and polished, Tom Schneider's 13-point deer likely was a pseudohermaphrodite.
If you kill what you suspect is an antlered doe, save the internal organs, then contact your local wildlife manager or veterinarian to request a thorough examination of the animal. You might be surprised by what they find.
Christopher DePerno, DNR Farmland Wildlife Populations & Research Group and Jonathan Jenks, South Dakota State University