THE EFFECT OF LATITUDE ON THE SEASONAL PATTERN OF REPRODUCTIVE HORMONES IN THE MALE WHITE-TAILED DEER

1. 1. In order to investigate the effect of latitude on the seasonal variability of reproduction, plasma levels of LH, FSH, Prolactin (PRL) and testosterone (T) were determined in 6 adult male white-tailed deer of Southern Ontario (latitude 42°N) and 6 deer of Southern Texas (27°N). 2. 2. LH peak (around 2 ng/ml) was found in Ontario deer in June; Texas values (almost 3 ng/ml) peaked in November. 3. 3. FSH maxima (110 ng/ml in Ontario and 100 ng/ml in Texas deer) were detected in August (Texas) and September (Ontario). 4. 4. PRL peak (around 90 ng/ml) was observed in Ontario in June. In Texas two peaks were observed; first (around 90 ng/ml) in May, the second one (around 50 ng/ml) in September-October. 5. 5. Testosterone exhibited sharp peaks in both groups; in Ontario in November (13 ng/ml) and in Texas in December (12 ng/ml). 6. 6. Significant differences between Ontario and Texas deer were found between timing of peaks of LH, PRL and T but not of FSH. © 1990.