Geographic variation in Thomas langur (Presbytis thomasi) loud calls

Abstract

Geographic variation in primate vocalizations has been described at two levels. First, at the level of acoustic variation within the same call type between populations and, second, at the level of presence or absence of certain call types in different populations. Acoustic variation is of interest because there are several factors that can explain this variation, such as gene flow, ecological factors and population density. Here we focus on the first level in a Southeast Asian primate, the Thomas langur. We recorded male loud calls in four populations that differed in their geographic distances from each other and had varying geographic barriers in between them, such as rivers and mountain ranges. The presence of these barriers leads to expectations of loud call variation under the gene flow model, which are examined here. We conducted a principal components analysis to condense the number of acoustic variables. With a subsequent discriminant function analysis on the six principal component scores, we found that the percentage of loud calls that were correctly assigned to a population was relatively high (50.0-76.2%) when three randomly selected loud calls from each male were used. Using the discriminant functions from this analysis to predict population membership of the remainder of the loud calls yielded lower, but still relatively high correct assignment percentages (26.2-66.7%). Analyses to examine the influence of barriers on similarities between populations confirm our expectations. We discuss that differences in loud calls are probably most parsimoniously explained by gene flow (or the lack thereof) between the populations and that future studies of genetic differences are crucial to test this hypothesis.

Call Cultures in Orang-Utans?

“…Thus our study differs from studies that examined geographic variation (or variation among captive groups) in acoustic characteristics of the same call type (e.g. [25], [26], [27], [28], [29], [30]). These between-population differences represent accents and not dialects, which is the focus of this paper [31].…”

“…We used a discriminant function analysis to determine whether a call could be correctly assigned to its call type based on its acoustic characteristics (cf. [27]). We conducted a separate analysis for nest smacks versus raspberries, and for throat scrapes versus harmonic uuhs.…”

From Grasping to Grooming to Gossip: Innovative Use of Chimpanzee Signals in Novel Environments Supports Both Vocal and Gestural Theories of Language Origins

“…The inclusion of calls in some locations, and its absence in others, in the same species, suggests that there is a social, learned component to some calls. This is a different phenomenon from group-based geographical differences in the acoustic structures of calls that are, themselves, displayed across groups, which is well established among some birds (e.g., Barrington 1773; Darwin 1871) and has more recently been widely reported among primate species (e.g., Crockford et al 2004;Green 1975;Marshall et al 1999;Wich et al 2008). There is increasing evidence that call repertoires are geographically distinct in two distinct ways: categorically different call repertoires, in which specific calls are present or absent in different populations, and contextually different uses of calls in different populations.…”

Unidirectional Microphone based Wireless Recorder for the Respiration Sound

“…The most popular microphones which the research groups employed in lung sound studies were Sony TM ECM-77B omnidirectional electret condenser microphone [1][2][3][4][5][6][7] and Sony TM ECM-T140 [8][9][10][11][12][13], and T150 electret condenser microphones with air coupler [14][15][16][17][18]. Observing the time sequence of the cited studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], the findings were that the applications of linguistics and voice recognition at first, and then the studies related to the lung sounds were continuously employed the Sony TM ECM-77B, T140, and T150 omnidirectional microphones. Was the adoption of microphones such as Sony TM ECM-77B, T140, and T150 evaluated by the paper survey or the considerations of the lung sound characteristics?…”