Condition and androgen levels: are condition-dependent and testosterone-mediated traits two sides of the same coin?

The immunocompetence handicap hypothesis posits that androgen-mediated signals honestly indicate the responsiveness of the immune system because of the immunosuppressive effect of androgens. However, androgen levels may also be related to nutritional status, and differences in body condition could be a more parsimonious explanation for variation in the expression of the signal. We maintained captive male red-legged partridges, Alectoris rufa, under regulated food shortage until they reached 85% of their initial body mass. Controls were provided with food ad libitum. After food shortage, experimental birds had lower androgen and higher corticosterone levels than controls. The condition dependence in androgen levels suggests that androgen-mediated signals could be indicating general nutritional state rather than immune function specifically. We propose that androgen-dependent signals may act as indicators of body condition or indicators of immune system quality, depending on the nutritional status of the individual.