The male song of the Javan silvery gibbon (Hylobates moloch)

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B 1Cn = 475%n = 38 %6 %CCCCn = 3284%n = 2774%n = 2080%n = 1682% 64 %54 %40 %32 %Cn = 3978 %B 110% n = 48 %1 2 3 4 5Rank of phrase note16 T. Geissmann et al. – The Male Song of the Javan Silvery GibbonB 2n = 5159 %B 3n = 3338 %(d)Fig. 7. (ctd.)B 1n = 48 %Cn = 3978 %49%43%15%24%61%B 2n = 2529 %Cn = 2226 %B 2n = 56 %B 3n = 89 %Cn = 2023 %36%52%45%27%60%75%55%25%20%B 2n = 910 %Cn = 1315 %B 2n = 1012 %B 3n = 67 %B 2n = 33 %Cn = 67 %B 2n = 1113 %B 3n = 56 %Cn = 44 %31%50%45%55%B 3n = 45 %B 2n = 56 %B 3n = 56 %Cn = 67 %1 2 3 4Rank of phrase note75%82%10%Cn = 36 %Cn = 3264 %B 1n = 48 %84%Cn = 2754 %74%Cn = 2040 %80%Cn = 1632 %1 2 3 4 5Rank of phrase note(e)Fig. 7. (ctd.)exhibits the highest transition probabilities betweensuccessive notes.The Kalejetan male was not included in thisanalysis because the shortness of the taperecordedsong fragment precluded the calculationof reliable transition probabilities. The high proportionof type C notes in the available songfragment (as described above, see Figure 3)suggests, however, that this male’s phrasestructure may resemble that of the Jakarta 2 male.Similar to the Howletts 1 and 2 males, 75% ofB 2n = 2620 %B 3n = 9775 %31%23%42%14%31%52%B 2n = 86 %B 3n = 65 %Cn = 118 %B 2n = 1411 %B 3n = 3023 %Cn = 5038 %67%45%45%57%36%57%37%40%12%42%Cn = 43 %B 2n = 54 %B 3n = 54 %B 2n = 86 %B 3n = 54 %B 3n = 1713 %Cn = 118 %B 2n = 2015 %B 4n = 65 %B 3n = 2116 %35%55%40%25%38%28%B 3n = 65 %B 3n = 65 %B 2n = 86 %B 3n = 54 %B 3n = 86 %Cn = 65 %50%50%B 3n = 43 %B 3n = 43 %1 2 3 4 5Rank of phrase note(f)Fig. 7. (ctd.)all phrases of the Munich male (Fig. 7f) beginwith a note of type B3. In contrast to other males,a C note follows on the second position (52%).Notes three, four and five of the phrases aremostly of type B3.The preferred note sequences in the phrases ofeach male are summarised in Table 6. In addition,the table also separately lists the results formultiple songs of the Jakarta 1 and Munich males.As can be seen in the list, the first note of thephrase remains of the same note type in all songbouts of the same male, but the phrase structure ofneither male is completely stable. At least in theMunich male, the differences in phrase structureare relatively moderate, considering that the thirdtape-recording (Munich 1c) was made 8 yearsafter the first one (Munich 1a).The proportions of the most common note sequences(one of each male) occurring in songphrases were compared among individual gibbonsusing minimum discrimination information statistics,revealing a strongly significant differenceamong the males (2I = 114.7, df=25, p
Contributions to Zoology, 74 (1/2) – 2005 17Table 6. The most frequently used order of note types in song phrases of each tape-recorded song bout.Tape-recording 1. note of phrase 2. note of phrase 3. note of phrase 4. note of phrase 5. note of phraseHalimun B2 B3 B3 B3 –Howletts 1 B3 B3 B3 B3 –Howletts 2 B3 B3 B3 B3 –Jakarta 1a B2 C B3 – –Jakarta 1b B2 B2 C B3 –Jakarta 1 total B2 B2 C B3 –Jakarta 2 C C C C CMunich 1a B3 C B3 C –Munich 1b B3 C B2 B2 –Munich 1c B3 B3 or C B3 B3 –Munich total B3 C B3 B3 B3DiscussionMale note repertoireOur study revealed that the note repertoire ofsilvery gibbon males appears to be much morecomplex than previously thought. The three notetypes defined by Kappeler (1984 a) are notsufficient to describe their vocal diversity. Wegrouped the male note repertoire of H. moloch intwo classes (expiration and inspiration notes). Theexpiration notes are further divided into fourgroups (labelled A through E), which are furtherdivided into distinct note types, resulting in a totalof 14 note types.Even this much larger number represents a conservativeapproach which cannot fully describe tothe vocal variability of the male songs of thisgibbon species. Especially the variable andinspiration notes (types D and E) could easily besplit into a larger number of distinct variants.Because these note types occur only rarely in thesongs that we analysed, a further subdivisionwould probably not have revealed additionalinsights in the song syntax.Wa notes (type B) are the dominant song notesin most males of this study. Similar wa notes arealso produced by other species of the genus Hylobates– such as H. lar (Raemaekers et al., 1984),H. muelleri and H. agilis (Haimoff, 1983) andusually represent the most common note type inthe repertoire of these species (Geissmann, ownobservation). The wa notes appear to be so typicalof the genus Hylobates (least of all H. pileatus)that this group might also be named the “wa notegibbons”.Composition of the song boutDespite their variability, male songs appear tofollow certain syntactical rules. Song boutstypically begin softly with several single oo notes(type A), which gradually develop into single wanotes (mostly type B1). The first phrasesoccurring in the song bout are short and simple,consisting of wa notes only. As the song boutcontinues, phrases become longer and more notetypes are included. This gradual developmentfrom simple oo notes to complex phrases can beseen in the completely sonagraphed (but unusuallyshort) song bout in Appendix 1. The progressiveelaboration appears to be typical of male solosongs of most (possibly all) gibbon species (e.g.Demars and Goustard, 1978; Goustard, 1976;Haimoff, 1984b, 1985; Mitani, 1988; Raemaekerset al., 1984; Tenaza, 1976; Whitten, 1982).Especially in the wa notes, a fine division intonote types is important: Whereas most wa notes atthe beginning of the song bout exhibit a smallrange of frequency modulation (note type B1), therange of most wa notes during the main songphase is more than twice as large (type B3).Phrase syntaxIt is difficult to identify a clearly preferred numberof notes per phrase – here termed song motivation– in a song bout. In the introductory phase, theaverage number of notes per phrase is usuallyshort and below 2 notes / phrase (single notephrases are included in this count, but inspirationnotes are not). The average phrase length in
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The male song of the Javan silvery gibbon (Hylobates moloch)

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