PHOTOPERIODIC CONTROL OF ANTLER CYCLES IN DEER .I. PHASE SHIFT AND FREQUENCY CHANGES

When subjected to reversed light cycles, deer antlers are shed and regenerated six months out of phase with respect to the outdoor environment. They respond solely to the lighting conditions, not to temperature changes. Deer exposed to accelerated years grow antlers more frequently than normal, but in no cases do they produce them more often than every three months. When the annual light cycle is prolonged to 24 months, deer tend to grow antlers every other year in accordance with the artificial cycle. In general, deer forced to grow antlers more frequently than normal produce stunted outgrowths owing to the abbreviated years. Those maintained on extra long light cycles, however, do not grow extra large antlers. Analysis of these data suggests that the onset of antler growth is entrained by increasing day lengths in deer previously sensitized by decreasing days. However, older animals can sometimes express an endogenous yearly antler growth cycle irrespective of certain prevailing artificial lighting conditions. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company