PHOTOPERIODIC CONTROL OF ANTLER CYCLES IN DEER .2. ALTERATIONS IN AMPLITUDE

Deer native to temperate zones grow new antlers each year in synchrony with the annual photoperiodic cycle. When the amplitude of this cycle is reduced from normal winter and summer solstices (at 42° latitude) of nine and fifteen hours to as little as eleven and one‐half and twelve and one‐half hours (equivalent to about 9° latitude), sika deer still tend to grow antlers on schedule, even when that schedule is accelerated. Deer exposed to days of constant length for prolonged periods of time fail to replace their antlers when the light:dark ratio is 12L/12D. When held on unchanging short (8L/16D) or long (16/8D; 24L/OD) days, however, they continue with their antler cycles at irregular intervals averaging about 85% of the siderial year. These results are interpreted in terms of an inherent circannian rhythm, the duration of which can be adapted to the frequency of the prevailing photoperiodicity, but which reverts to approximately a year on constant long or short days and disappears altogether on simulated equatorial photoperiods. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company