Physalaemus nanus (Boulenger, 1888)

Hepp, Fábio & Pombal, José P., 2020, Review of bioacoustical traits in the genus Physalaemus Fitzinger, 1826 (Anura: Leptodactylidae: Leiuperinae), Zootaxa 4725 (1), pp. 1-106 : 40-43

Physalaemus nanus (Boulenger, 1888)

We found three different calls, referred to as call A, B, and C ( Fig. 12 ). Calls B and C were common in recordings in which several males were active and calling close to each other. Calls A and B are composed of harmonics and a single note each. Call B is shorter than Call A with a lower fundamental frequency, irregular FM segments, and absence of pulse-PAM. Call C is composed of two notes, the first and the second notes are similar to those of calls A and B, respectively.

Call A ( Fig. 12 E–H and 13A). We examined 20 recordings, a total of 77 minutes, with ca. 3500 calls from 33 males. Only some of these calls were measured (see Table 2 ). Call duration varies from 0.178 to 0.218 s. The call envelope is variable; however, calls often have rise, a regular sustain (or shallow valley), and falls sections. Call rise and fall are usually gradual and linear but they can have different durations, being long or abrupt. The amplitude peak of the calls measured here is at around the end of the first fourth of the call duration ( Fig. 12A, C, D, E ). The envelope of the call can be elliptic ( Fig. 12A, D ), rectangular ( Fig. 12E ), or triangular ( Fig. 12C ). More than 50 % of the energy is concentrated in 42 % of the call duration around the amplitude peak. This call has a strong PAM (with silence intervals present between pulses; Fig. 12 A–H). The rate of the PAM is ca. 28 Hz, forming ca. five pulses throughout the call. The envelope of the pulses is also highly variable; however, the middle pulses tend to have amplitude peak at the middle of the pulse with similar rise and fall. Often, the first pulse has very little amplitude and the last pulse is the longest one ( Fig. 12C, D, F, G ). Silence intervals are present between pulses, slightly shorter than pulse duration ( Fig. 12 A–H). Some pulses have a down-upward AM at the middle of their durations, yielding two amplitude peaks per pulse. The call has a harmonic series ( Fig. 13A ). The fundamental frequency varies from 620 to 1100 Hz and the band can be present with low energy or absent in the audiospectrograms. The wave periods are regular and then the harmonics are clear throughout the call. Subharmonics can be present at the beginning and end of the pulses and jumps of the fundamental frequency can happen at the end of the call (fourth pulse in Fig. 12B ). The dominant frequency varies from ca. 2240 to 2540 Hz ( Fig. 12B ). The dominant harmonic varies from the second to the fourth one, but it is usually the second. There is no clear shift in the relative energy among the bands throughout the call. Most of the energy is concentrated between 1800 and 2800 Hz (ca. two harmonics). The frequency bands have a general and slight downward FM throughout the call ( Fig. 12B ). Additionally, there is PFM throughout the call, which is directly proportional to the synchronic pulse-PAM ( Fig. 12 A–H).

Call B ( Fig. 12 I–N and 6D). We examined five recordings, a total of 27 minutes, with ca. 40 calls from 13 males. Only some of these calls were measured (see Table 2 ). Call duration varies from 0.027 to 0.090 s. Often, the call rise is longer than the fall, both exponential; there is a long regular sustain (or shallow valley) between them. The amplitude peak is at around the end of the first three fourths of the call duration ( Fig. 12I, K, L ). The envelope of the call varied from rectangular ( Fig. 12K ) to triangular (pointed left; Fig. 12I, L ). More than 50 % of the energy is concentrated in 31 % of the component duration around the amplitude peak. This call has no PAM. The call has a harmonic series ( Fig. 6D ). The fundamental frequency is ca. 300 Hz and this band can be present with low energy or absent in the audiospectrograms. Usually, the wave periods are regular and then the harmonics are clear throughout the call. However, harmonics are not very clear with considerably deterministic chaos in some parts of the call ( Fig. 12N ). Sudden jumps of the fundamental frequency can be present (usually at the end of the call). Moreover, some calls show subharmonics ( Fig. 12N ). The dominant frequency varies from ca. 1680 to 1850 Hz ( Fig. 12J ). The dominant harmonic varies from the seventh to the 41 st, but it is usually the ninth or tenth. There is no clear shift in the relative energy among the bands throughout the call. Most of the energy is concentrated between 1300 and 2200 Hz (three or four harmonics). The frequency bands can have a general down or upward FM throughout the call with either short down or upward FM at the end ( Fig. 12J, M, N ). Some calls have no clear general FM. Additionally, some calls have a subtle PFM throughout the call ( Fig. 12J, M, N ).

Call C ( Fig. 12 O–T and 6E). We examined 16 recordings, a total of 60 minutes, with ca. 200 calls from 28 males. Only some of these calls were measured (see Table 2 ). Calls are composed of two notes, the first and the second are similar to those of calls A and B, respectively. Call duration varies from 0.188 to 0.311 s. The amplitude, temporal, and spectral traits of the components are similar to those described above. However, the first note can have more pulses and the envelope of the second note has steeper rise and fall in call C ( Fig. 12O, Q, R ). Although the amplitude decreases at the transition between notes, their limits are not clear ( Fig. 12Q, R ). At this transition, there is a decrease in the fundamental frequency and wave peaks emitted at low repetition rates (e.g., 90 Hz) are shown as clicks (instantaneously high sound-pressure effect; Fig. 12P ) in audiospectrograms at broad filter bandwidths (e.g., above 100 Hz). The bands are observed in audiospectrograms at narrow filter bandwidth (e.g., below 90 Hz). This rate gets faster until the beginning of the center of the second note. In C calls, the harmonics of the second note usually have a general upward FM with a short downward FM at the end of the call ( Fig. 12P but see Fig. 12S, T ).

Figures

FIGURE 6. Multiplicity relationship between “instantaneous” dominant frequency and w of calls B and C of six Physalaemus species. Each graph shows a single call. Call B of P. maculiventris (A), call B of P. erythros (B), call B of P. ruspestris (C), call B of P. nanus (D), call C of P. nanus (E), and call B of P. spiniger (F). Grid corresponds to the harmonic values (right y-axis). Red squares are the values of “instantaneous” dominant frequency; blue circles are the values of the reciprocal of w; green triangles are the factor values of the ratio “instantaneous” dominant frequency / w reciprocal per delta time. Delta time corresponds to the duration of one period of the measured acoustic oscillation. Note that factors around integer values suggest harmonic relationship between the frequency calculated (w reciprocal) and the dominant frequency.

FIGURE 12. Calls A, B, and C of Physalaemus nanus. Oscillograms (A, C–E, I, K–L, O, and Q–R) and audiospectrograms (B, F–H, J, M–N, P, and S–T). A single typical call A (A and B). Variant calls A with different envelopes, number of pulses, pulse durations, and interpulse intervals (C–H). Calls B (I–N). Calls C (O–T). Horizontal scale bars have 0.05 s (A–H), 0.02 s (I–N), and 0.2 s (O–T); vertical scale bars have 1 kHz. Filter bandwidth (Hz): 181.0 (B and H); 162.0 (F); 110.0 (G); 124.0 (J, M, and P); 106.0 (N); 84.6 (S); 92.1 (T).

FIGURE 13. Multiplicity relationship between “instantaneous” dominant frequency and w of calls A of eight Physalaemus species. Each graph shows a single call A of: P. nanus (A), P. spiniger (B), P. crombiei (C), P. signifer (D), P. bokermanni (E), P. angrensis (F), P. atlanticus (G), P. moreirae (H). Grid corresponds to the harmonic values (right y-axis). Red squares are the values of “instantaneous” dominant frequency; blue circles are the values of the reciprocal of w; green triangles are the factor values of the ratio “instantaneous” dominant frequency / w reciprocal per delta time. Delta time corresponds to the duration of one period of the measured acoustic oscillation. Note that factors around integer values suggest harmonic relationship between the frequency calculated (w reciprocal) and the dominant frequency. Factors multiple of ½ of the fundamental frequency correspond to subharmonics (see P. nanus; A).