Induction of antler growth in a congenitally polled Scottish red deer stag.

A congenitally polled red deer stag was captured from a Scottish deer forest and kept in an enclosure for observations. The animal had rudimentary antler pedicles but no antlers, and during five years of study no significant antler development occurred. Amputation of the apex of one antler pedicle in May 1974 when the stat was 12 years of age resulted in the growth of a complete antler on the operated side, and this antler was subsequently cleaned and cast in the normal way and a new antler cycle was initiated. The result illustrates that the primary abnormality in this polled stag lay not in his inability to grow antler, but in his inability to develop fully formed antler pedicles from which normal antler tissue could differentiate. Traumatizing the rudimentary pedicle had the effect of stimulating growth of antler tissue, and once this was formed the process of cleaning, casting and regrowth occurred spontaneously. The incomplete development of the antler pedicles is considered to be responsible for the absence of antlers in the majority of "hummels" in Scotland, and the etiology of the condition is discussed.