Social signals influence hormones independently of calling behavior in thetreefrog (Hyla cinerea)

Social signals play an important role in regulating hormone-behavior relati onships. In anurans (frogs and toads), acoustic signals are an essential as pect of reproductive behavior; however, the physiological consequences of r eceiving social signals has remained largely undescribed. Each night for 5, 10, or 20 days, we presented acoustically isolated male treefrogs with a c onspecific mating chorus, an array of tones, or no sound. We recorded calli ng rate of individuals throughout the experiment and collected blood before and after treatment. Days of stimulus exposure had no effect on any depend ent measure. Acoustic treatment influenced steroid levels; testosterone, di hydrotestosterone, and corticosterone increased only in the group exposed t o the chorus. Chorus-exposed males also showed an increase in stimulus-evok ed calling. We found no correlation between androgens and calling within ea ch treatment group. In addition, noncallers in the chorus group had higher levels of androgens than males in the tone or no sound groups. Further, cho rus-exposed males with zero, low, or high rate of calling had similar level s of androgens. These data indicate that social signals increase circulatin g androgens independently of calling behavior. Elevated corticosterone asso ciated with chorus reception did not inhibit calling behavior, and corticos terone showed no correlation with androgen levels. (C) 2000 Academic Press.