A comparison of facial expression properties in five hylobatid species: facial expressions in hylobatids

Scheider, L, Liebal, K, Oña, L, Burrows, A and Waller, B ORCID: https://orcid.org/0000-0001-6303-7458, 2014. A comparison of facial expression properties in five hylobatid species: facial expressions in hylobatids. American Journal of Primatology, 76 (7), pp. 618-628. ISSN 0275-2565

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Abstract

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.

Item Type:	Journal article
Publication Title:	American Journal of Primatology
Creators:	Scheider, L., Liebal, K., Oña, L., Burrows, A. and Waller, B.
Publisher:	Wiley
Date:	July 2014
Volume:	76
Number:	7
ISSN:	0275-2565
Identifiers:	Number Type 10.1002/ajp.22255 DOI 1383894 Other
Divisions:	Schools > School of Social Sciences
Record created by:	Linda Sullivan
Date Added:	03 Nov 2020 12:26
Last Modified:	31 May 2021 15:14
URI:	https://irep.ntu.ac.uk/id/eprint/41470

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