RELATIONSHIP OF PHOTOPERIOD TO PUBERTY IN DOE FAWN WHITE-TAILED DEER

Experiments on doe fawn white-tailed deer (Odocoileus virginianus) in Upper Michigan [USA] revealed that artificially long days (16L:8D) in autumn did not induce a greater fertility rate compared to short-day (natural daylight) controls. Eleven (61.1%) of 18 long-day doe fawns became pregnant and carried fawns to term, vs 8 (72.7%) of 11 short-day controls. However, onset of puberty (i.e., estrus) tended to be delayed among long-day specimens compared to the controls. Data support the concept of a doe fawn''s critical fat/lean biomass ratio regulating the temporal onset of puberty. In northern climes, nutritional constraints rather than rapidly diminishing photoperiod probably serve to curtail folliculogenesis, resulting in a low fertility rate among doe fawn deer.