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Research on captive and wild great apes has established that they employ large repertoires of intentional gestural signals to achieve desired goals. However, gestural research has focused on African great apes, with orang-utan data limited to a few captive studies. We address this gap by describing gesture use in wild Southwest Bornean orang-utan (Pongo pygmaeus wurmbii) mother and offspring pairs. We conducted focal follows on 16 individuals in the Sabangau peat-swamp forest in Borneo, Indonesia. The resulting 681 h of video footage yielded 1299 communicative signals: 858 vocal signals and 441 gestural signals. Eleven vocal signal types and 21 gesture types met the criteria for inclusion in the repertoire; however, the gestural repertoire did not approach asymptote and further gesture types will likely be identified in the future. Signalers used gestures of any modality in higher frequency when the recipient was paying visual attention, and took the recipient's visual attention into account when selecting gesture modalities. Orang-utans employed hands and arms more than legs and feet in gesturing, but were more flexible in their choice of limb than chimpanzees using the same gestures. Orang-utans were highly responsive to gestural requests, using them to achieve eight goals and, where successful, responding either before gesturing ended or in <1 s in 90% of communications. Our findings on the range of gesture types and impact of visual attention support findings from captive orang-utans; and those on responsiveness and limb use highlight the importance of studying ape communication in the social and ecological context to which it is adapted. [ABSTRACT FROM AUTHOR]

We investigated phylogenetic relationships among populations of two species within the genus Leptophryne, L. cruentata and L. borbonica, using the mitochondrial 16S rRNA gene. As a result, we identified two distinct lineages within populations currently considered Leptophryne cruentata: 1) a lineage containing L. cruentata from the type locality, and 2) a lineage from Mt. Slamet and Mt. Ciremai. On the basis of genetic and morphological differences, we describe the Mt. Slamet and Mt. Ciremai populations as a new species, L. javanica sp. nov. The new species is distinguished from L. cruentata and L. borbonica by the following combination of morphological characters: the presence of distinct yellow mottling on the dorsum; relatively small body size (SVL male 22.2-24.0 mm, female 29.6 mm); relatively short hindlimbs (HLL 37.0-40.9 mm); relatively short fourth toe (4ToeL 4.3-6.0 mm); basal webbing on the hands, but well developed on toes; very protruding snout and an indistinct tympanum. In our preliminary phylogenetic analysis, we also detected four distinct lineages within Leptophryne borbonica: 1) a lineage containing true L. borbonica from west Java, 2) a lineage from Lampung (Sumatra I), 3) a lineage from northern Borneo, and 4) a lineage from Bengkulu (Sumatra II). Further studies are needed to determine taxonomic status of these lineages.

In this study, we examine acoustic individuality in male duet songs of wild, non-habituated Bornean southern gibbons (Hylobates albibarbis) and identify contributing acoustic variables. We recorded 174 male duet songs from nine groups in a rainforest in Central Kalimantan, Indonesia. Each male portion of the duet was analysed for 14 acoustic variables at three levels of variation, including six note-specific variables (start frequency, end frequency, minimum frequency, maximum frequency, average frequency and duration), four phrase-specific variables (minimum frequency, maximum frequency, duration and number of syllables) and four song-specific variables (minimum frequency, maximum frequency, duration and number of syllables). Principal component analysis was performed to summarise each of these sets of variables into a total of six principal components (PCs). Strong acoustic individuality was found in all PCs and at all three levels: note, phrase and song (all p < 0.001). Furthermore, a particularly high magnitude of individuality was found in PC 1 of the song-specific analysis, defined by the acoustic variables of duration and number of syllables. Due to the high levels of individuality, we suggest that these acoustic variables may be used by Bornean southern gibbons for individual discrimination. As well as furthering our biological understanding of male gibbon song with regards to individuality and associated conspecific recognition, these findings also have the potential to help improve population survey methods, such as the acoustic sampling method using listening points, by offering a more accurate method of individual recognition.