Androgens modulate song effort and aggression in Neotropical singing mice.

Androgens are an important class of steroid hormones involved in modulating the expression and evolution of male secondary sex characters. Vocalizations used in the context of aggression and mate attraction are among the most elaborate and diverse androgen-dependent animal displays as reflected in a rich tradition of studies on bird song and anuran calls. Male Alston's singing mice (Scotinomys teguina) commonly emit trilled songs that appear to function in male-male aggression. In this study, we experimentally manipulated androgens in singing mice to assess their role in modulating aggression and song effort. Testosterone- and DHT-treated animals retained aggressive and song attributes similarly. However, castrated mice administered empty implants showed more subordinate behavior and sang fewer songs that were shorter, lower in power, higher in frequency, and less stereotyped. The extensive effects of androgens on a suite of phenotypes highlight their role in linking gonadal status with decisions about investment in reproductive behaviors.