fat bodies and visibly undifferentiated gonads. These froglets are covered with many small dark spots and have much less webbing in the fingers and toes as compared to adult frogs. After metamorphosis, the froglets leave the water. Individuals of this species can reach sexual maturity in one year. Reproduction in H. rosenbergi is influenced by both social and environmental factors. Females of the species have been found to be influenced by the social cue of the current chorus size in moderating their reproductive activity, while males have been found to be influenced both by same day precipitation (with heavy rainfall decreasing activity) and previous day chorus size. Mating The breeding season of H. rosenbergi runs from March through May. The mating system for H. rosenbergi revolves around a nest occupied by the male. Once nests are constructed, males call from within the nest during the nighttime, calling only a few nights over a one-week period. In particular, males produce an advertisement call, described as a “tonk-tonk-tonk” sound of three notes, to attract gravid females. This advertisement call has socially mediated plasticity, as the presence and distance of competing males influences the calling rate. As competition in the form of the number of nearby males or attractiveness of nearby males increases, male individuals of this species increase their calling rate. In addition, nearest neighbor males have similar call rates, indicating that they adjust their call rates to each other. The advertisement call is usually called in small groups. During pair formation, the female responds to the male’s advertisement call by approaching and entering the male’s nest opposite the male’s back, at which time the male stops calling or switches to a courtship call longer in duration than the advertisement call. The female then swims around the nest and spends time inspecting it. In the Panamanian population, some females were observed renovating the nest, but this was not found in the Costa Rican population. At the end of the inspection period, if the female decides to mate with the male, the female will massage the male with her chest through a swimming motion and patting her hands, after which the male will mount the female to initiate amplexus. The male then clasps both sides of the female’s neck, as the female is completely submerged except for the cloacal opening. Amplexus lasts for approximately 10 minutes, after which the eggs spread across the