Sound pressure levels and radiation patterns of the vocalizations of some North American frogs and toads

Abstract

Sound pressure levels of the vocalizations of 21 species of North American anurans were measured in the field. In most species the peak levels at 50 cm in front of the male exceeded 100 dBre 2×10−4 μbar (Table 2). The sound pressure levels of the calls of most individuals varied by less than 2.5 dB, but intraspecific variation was significantly higher, averaging about 8.5 dB (Tables 1, 2). Sound pressure levels of mating calls were positively correlated with body size in the toad,Bufo americanus (Fig. 2); however, interspecific differences in sound pressure levels were not clearly related to interspecific differences in body size. Measurements of directivity patterns indicated that sound fields around three males ofHyla crucifer were uniform, whereas two males ofH. chrysoscelis represented directional sound sources (Table 3).