Annual cyclicity in the squirrel monkey (Saimiri sciureus): The relationship between testosterone, fatting, and sexual behavior

The relationship between seasonal sexual activity, endogenous testosterone, and weight changes (fatting) in the squirrel monkey (Saimiri sciureus) was assessed. Adult males were shown to have an annual rhythm in testosterone levels which coincides with peak sexual activity. Fatting was shown to occur in both adult males and adult females seasonally. However, fatting preceded both heightened sexual activity and increases in endogenous testosterone concentrations. In addition the frequency of eating and drinking do not show a consistent correlation with weight change in males and females. Therefore, the seasonal fatting response in squirrel monkeys must be due to mechanisms other than altered rate of consumption or increased production of testosterone.