Seasonal levels of cortisol, IGF-1 and triiodothyronine in adult male pudu (Pudu puda)

Seasonal levels of cortisol (C), insulin-like growth factor 1 (IGF-1) and triiodothyronine (T-3) were determined in plasma of six adult male pudu (Pudu puda). Cortisol concentrations, which varied from 0.6 to 1.7 mu g.100ml(-1), exhibited two peaks. The first one, detected in March (fall), was higher than the second one in August (winter). A significant decrease in C concentrations was detected between three consecutive samples taken ten minutes apart. Levels of IGF-1 were maintained low (146-186 ng.ml(-1)) between December (summer) and March. After a few months rise, IGF-1 reached peak levels (290 ng.ml(-1)) in October (end of the antler growth period). Unlike in large cervid species, T-3 levels (1-1.2 ng.ml(-1)) were maintained between December and May. It is speculated that solitary life style and the local climatic conditions.