The advertisement call of Eleutherodactylus johnstonei consists of two adjacent notes (two tones or frequency components). It is, on average, 314 ms in duration, with the first note shorter than the second (86 and 223 ms respectively). The intercall interval is 1.42 s which corresponds to 46,7 calls/min. The dominant frequency of the first note is 1.8 kHz and that of the second note is 3.18 kHz. Both notes contain harmonic series (up to 5 harmonics in the first note and 3 in the second), with narrow bands of constant frequency except for a short and abrupt (38 Hz/ms) upward modulation at the beginning of the second note. Most of the energy of each note is contained in the fundamental band. Spectral characters vary much less than temporal characters, as in other anurans, but variation of spectral characters is amongst the lowest reported so far (~ 1%). There is a weak negative correlation between body mass and the dominant frequency of the call (r = −0.52); therefore call frequency may indicate male size, though to a limited extent. Advertisement calls described here have lower frequencies than those of other localities in the Lesser Antilles and mainland South America. Further research is needed to clarify this issue. Click calls are emitted sporadically in groups of up to four clicks, and are not preceded by introductory notes. Click duration and dominant frequency are, on average, 31 ms and 3.01 kHz, respectively. However, the first and last clicks within a group have lower frequencies than the others. There is substantial variation in the spectral structure of clicks, both within and among groups. All traits have considerable variation (> 10%) except for the frequency of central clicks of a group.
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Vol. 3 • No. 3