Mating vocalizations of female frogs: Control and evolutionary mechanisms

Vocalization behaviors of anuran amphibians are universally sexually dimorp hic. Usually, only male frogs give an advertisement call, while female frog calls are limited to a soft and simple release call which is specifically suppressed at mating. In a very few species, however, female frogs also giv e mating vocalizations, We examined possible mechanisms for control of this rare heterotypical behavior. At the peripheral level, most differences in temporal and spectral characteristics between female mating calls and the c alls of conspecific males related directly to sexual dimorphisms in larynge al and oblique muscle morphology. At the neural and hormonal level, we firs t developed an integrated model for control of vocalizations, based primari ly on male frog data, When this model is applied to females, female mating vocalizations were most similar to male advertisement calls, rather than be ing modified release calls. Females may have conscripted preexisting androg en-sensitive neural pathways typically used only by males but present in bo th sexes. Female mating calls have been heard only during courtship and amp lexus. Androgen levels in females at this time are significantly higher tha n even those levels in males. Because this situation is common in frogs, fe male mating vocalizations likely evolved independently multiple times. Char acter optimization suggests that mate location is the most common biologica l role for female mate calling, but the particular aspects of reproductive biology vary widely across species.