A comparison of facial expression properties in five hylobatid species

Little is known about facial communication of lesser apes (family Hylobatidae) and how their facial expressions (and use of) relate to social organization. We investigated facial expressions (defined as combinations of facial movements) in social interactions of mated pairs in five different hylobatid species belonging to three different genera using a recently developed objective coding system, the Facial Action Coding System for hylobatid species (GibbonFACS). We described three important properties of their facial expressions and compared them between genera. First, we compared the rate of facial expressions, which was defined as the number of facial expressions per units of time. Second, we compared their repertoire size, defined as the number of different types of facial expressions used, independent of their frequency. Third, we compared the diversity of expression, defined as the repertoire weighted by the rate of use for each type of facial expression. We observed a higher rate and diversity of facial expression, but no larger repertoire, in Symphalangus (siamangs) compared to Hylobates and Nomascus species. In line with previous research, these results suggest siamangs differ from other hylobatids in certain aspects of their social behavior. To investigate whether differences in facial expressions are linked to hylobatid socio-ecology, we used a Phylogenetic General Least Square (PGLS) regression analysis to correlate those properties with two social factors: group-size and level of monogamy. No relationship between the properties of facial expressions and these socio-ecological factors was found. One explanation could be that facial expressions in hylobatid species are subject to phylogenetic inertia and do not differ sufficiently between species to reveal correlations with factors such as group size and monogamy level. Am. J. Primatol. 76:618-628, 2014

Gibbon classification : the issue of species and subspecies

Gibbon classification at the species and subspecies levels has been hotly debated for the last 200 years. This thesis explores the reasons for this debate. Authorities agree that siamang, concolor, kloss and hoolock are species, while there is complete lack of agreement on lar, agile, moloch, Mueller\u27s and pileated. The disagreement results from the use and emphasis of different character traits, and from debate on the occurrence and importance of gene flow

Preliminary investigation of flexibility in learning color-reward associations in gibbons (<i>Hylobatidae</i>)

Previous studies in learning set formation have shown that most animal species can learn to learn with subsequent novel presentations being solved in fewer presentations than when they first encounter a task. Gibbons (Hylobatidae) have generally struggled with these tasks and do not show the learning to learn pattern found in other species. This is surprising given their phylogenetic position and level of cortical development. However, there have been conflicting results with some studies demonstrating higher level learning abilities in these small apes. This study attempts to clarify whether gibbons can in fact use knowledge gained during one learning task to facilitate performance on a similar, but novel problem that would be a precursor to development of a learning set. We tested 16 captive gibbons' ability to associate color cues with provisioned food items in two experiments where they experienced a period of learning followed by experimental trials during which they could potentially use knowledge gained in their first learning experience to facilitate solution I subsequent novel tasks. Our results are similar to most previous studies in that there was no evidence of gibbons being able to use previously acquired knowledge to solve a novel task. However, once the learning association was made, the gibbons performed well above chance. We found no differences across color associations, indicating learning was not affected by the particular color / reward association. However, there were variations in learning performance with regard to genera. The hoolock (Hoolock leuconedys) and siamang (Symphalangus syndactylus) learned the fastest and the lar group (Hylobates sp.) learned the slowest. We caution these results could be due to the small sample size and because of the captive environment in which these gibbons were raised. However, it is likely that environmental variability in the native habitats of the subjects tested could facilitate the evolution of flexible learning in some genera. Further comparative study is necessary in order to incorporate realistic cognitive variables into foraging models

Social Polyandry Among Siamangs: The Role Of Habitat Quality

In species where females do not associate spatially with other females, males usually range over an area including the home ranges of multiple females or defend the home range of one female. Nevertheless, social polyandry (multimale–unifemale grouping) occurs in some species. We examine an ecological constraints model relating habitat quality to facultative social polyandry in siamangs, Symphalangus syndactylus, by testing predictions of two hypotheses: (H1) variation in the size and density of important food trees affects the size of siamang home ranges and areas of exclusive use; (H2) socially polyandrous groups benefit from cooperative defence of the home range and area of exclusive use. Crown volume/ha of freestanding or strangler figs (Ficus), the most important siamang food, was negatively related to the size of the home range but not to the size of the area of exclusive use. Density and crown volume/ha of the second-most important plant food, Dracontomelon dao, was not related to the size of the home range or to the size of the area of exclusive use. Multimale groups had larger home ranges and areas of exclusive use than unimale groups, and the home ranges and areas of exclusive use of multimale groups encompassed more freestanding or strangling figs than those of unimale groups. Models of home range size including fig abundance (density or crown volume/ha) and the number of males as predictor variables suggested that multimale groups have larger home ranges than predicted by the relationship between fig abundance and home range size alone. While some other facultatively polyandrous species have larger home ranges in areas of poorer habitat quality, our results suggest a more complex situation for siamangs at our study site. Specifically, the density of large figs may constrain siamang ranging patterns, but multimale groups live in home ranges with more figs than those of unimale groups. Our results suggest that multimale groups may defend higher-quality territories than unimale groups

Environment and Time as Constraints on the Biogeographical Distribution of Gibbons

We develop a time budget model for the hylobatid family with the aim of assessing the extent to which their contemporary and historical biogeographic distributions might be explained by ecological constraints. The model uses local climate to predict time budgets, and from this the limiting size of social group that animals could manage at a given location. The model predicts maximum group sizes that vary between 3-15 within the taxon’s current distribution, indicating that the combination of their dietary and locomotor styles with the kinds of habitats they inhabit radically constrain group size. Beyond the edges of their current distribution, sustainable group size rapidly tends to zero, although if they had been able to bypass some of these areas, they would have found very suitable habitats in southern India and beyond the Wallace Line. While travel time would be a major constraint on group size at larger group sizes, as it is in great apes, the main factor limiting the gibbon’s current distribution is the time they need to spend resting that is imposed on them by the environment. The model also indicates that gibbons would not now be able to survive in regions of central and southeastern China where they are known to have occurred within historical times, perhaps because historical climate change following the Little Ice Age of the C18th made these regions uninhabitable for them. Finally, our results indicate that gibbons have the ecological capacity to live in larger groups than they do, making it unlikely that their adoption of monogamy reflects purely ecological constraints

Morning call of siamang (Symphalangus syndactyllus) in Subayang River, Riau – Indonesia

Morning call in siamang is very important for the&nbsp; life of siamang. This behavior is important to mark its territory, communicate with neighboring groups, etc. The this research aims to determine the time of vocalization, the position of trees and the strata canopy used by gibbons in vocalization. This research was conducted in WWF Indonesia Central Sumatra Research Station Subayang Camp at Rimbang Baling Wildlife Reserve for 2 months from July until August 2017 using Visual Encounter Survey (VES) method. From this research we knew that morning call in siamang&nbsp; usually occurs from 08.00 am – 10.00 am in the morning. Siamang appears to choose emergent tree in the forest ridge or emergent tree on the hill slope to do vocalization. &nbsp;During vocalization, siamang tends to use the 3rd and the 4th strata or upper canopy layer and emergent layer which are&nbsp; higher than 20 m from the forest surface. This height facilitates the siamang to maximize transmission of the vocalization to the surrounding area and communicate with other groups

Flowers Are An Important Food For Small Apes In Southern Sumatra

Flowers are included in the diets of many primates, but are not generally regarded as making an important contribution to primate energy budgets. However, observations of a number of lemur, platyrrhine, and cercopithecine populations suggest that some flower species may function as key primate fallback foods in periods of low abundance of preferred foods (generally ripe fruits), and that flowers may be preferred foods in some cases. I report heavy reliance on flowers during some study months for a siamang (Symphalangus syndactylus) population in southern Sumatra. Siamangs at Way Canguk spent 12% of feeding time eating flowers from October 2000 to August 2002, and in 1 month flower-feeding time exceeded 40% of total feeding time. The overall availabilities of fig and nonfig fruits, flowers, and new leaves in the study area were not significant predictors of the proportion of time that siamangs spent consuming any plant part. However, flower-feeding time was highest in months when nonfig fruit-feeding time was lowest, and a switch from heavy reliance on fruit to substantial flower consumption was associated with a shift in activity patterns toward reduced energy expenditure, which is consistent with the interpretation that flowers may function as a fallback food for Way Canguk siamangs. Hydnocarpus gracilis, a plant from which siamangs only consume flowers, was the third-most-commonly consumed plant at Way Canguk (after Ficus spp. and Dracontomelon dao), and flowers from this plant were available in most months. It is possible that relatively high local availability of these important siamang plant foods is one factor promoting high siamang density in the study area

Ode to our musical origins

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Graduate Program in Science Writing, 2010."September 2010." Cataloged from PDF version of thesis.Includes bibliographical references (p. 29-32).Music is part of human culture and has been around for several thousand years. In spite of its strong emotional appeal, the history of this human characteristic, and the source of its allure remain elusive. This thesis is a report from the front lines of research into the origins of human music, presenting four popular scenarios for the source of music. Music is treated as a homolog for gibbon song, as a co-evolver with language, as a sexually selected adaptation and as a cultural artifact that elicits universally reaching, culturally exclusive emotional responses from listeners.by Nidhi Subbaraman.S.M.in Science Writin

Patterns Of Dispersal In Sumatran Siamangs (Symphalangus syndactylus): Preliminary mtDNA Evidence Suggests More Frequent Male Than Female Dispersal To Adjacent Groups

Gibbons of both sexes have been observed emigrating from their natal groups, but the consequences of dispersal in gibbons are poorly understood, and it is unclear whether these are the same for both sexes. I sequenced a 350-bp fragment of mitochondrial DNA from 18 adults in seven siamang (Symphalangus syndactylus) groups at the Way Canguk Research Station in southern Sumatra to assess patterns of matrilineal relatedness among and within siamang groups, and to assess their fit with different patterns of sex-specific dispersal. A total of 11 haplotypes were identified in the seven study groups; 50% of adult males in five contiguous groups shared a haplotype with a member of an immediately adjacent group, whereas only 16.7% of females shared a haplotype with a neighbor. The apparent difference persisted if only same-sex individuals were considered (37.5% of males vs. 0% of females). Four of the seven study groups contained two adult males and a single adult female. In three multimale groups, the three adults all had different haplotypes, suggesting that neither male was the retained adult offspring of the female, whereas in the fourth group, the haplotype of one male was identical with that of the adult female. The high diversity of haplotypes and the absence of clustering among female haplotypes in the study neighborhood suggest that female dispersal to territories adjacent to the natal group may be relatively rare. The presence of some clustering of male haplotypes suggests that shorter dispersal distances may be more common in males