Boophis occidentalis

Vences, Miguel, Andreone, Franco, Glos, Julian & Glaw, Frank, 2010, Molecular and bioacoustic differentiation of Boophis occidentalis with description of a new treefrog from north-western Madagascar, Zootaxa 2544, pp. 54-68 : 59

Vocalizations of Boophis occidentalis and bioacoustic comparisons

Advertisement calls of B. occidentalis were recorded from a single, isolated male (ZSM 2314/2007 [ZCMV 5551]) in the Namazaha Valley at Isalo National Park on 15 February 2007, ca 21:00 h, at an estimated air temperature of 25° C. When the recordings were taken, no additional males were calling or interacting with the calling male at this site. Nevertheless, the male appeared to be highly motivated and was repeating its call multiple times. Furthermore, at other sites along the same stream, at least 100 m from the first site, we heard additional single males (at least one specimen but probably several) emitting the same calls, but these specimens were too difficult to approach and collect due to the depth and current of the stream.

The calls (figure 3) were unharmonious, pulsed notes emitted in short regular series. Notes were composed of 50–66 (57±4.3, n=12) pulses. Note duration was 856–1112 ms (996±68.8 ms, n=12), duration of intervals between notes of a regular note series was 534–1164 ms (785±236.8 ms, n=10), with longer intervals between regular note series (2073 and 4210 ms, n=2). Duration of pulses was 7–14 ms (10.8±2.1 ms, n=14), duration of intervals between them was 2–13 ms (5.1±3.0 ms, n=14). No click pulses were recognized. Pulse repetition rate was 53–60 pulses per second. Frequency was 500–1050 Hz, with a dominant frequency band between 560–750 Hz.

A comparison with calls from Berara which have been described (under the name B. occidentalis ) and recorded in a chorus situation ( Andreone et al. 2002) reveals that the latter differs from the Isalo calls by less pulses per note (26–34 vs. 50–66), shorter note duration (262–362 ms vs. 856–1112 ms), a higher pulse repetition rate (90–109 vs. 53–60 per second), and higher frequency range (900–2000 Hz vs. 500–1050 Hz).

Because the data from Isalo are based on vocalizations of a single specimen, the variation of calls of this population still needs to be fully assessed. However, (1) at least one additional male was heard at Isalo and the calls sounded very similar to that of the recorded specimen (in fact, it is possible for human receivers to easily recognize the temporal call differences between the populations), and (2) of numerous males recorded at Berara , none emitted the slow and long calls recorded at Isalo. We therefore conclude that these differences very probably represent a constant bioacoustic differentiation among these populations, confirming the specific distinctness of the candidate species from Berara which is described in the following: