Primate Conservation Msc
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Primate Conservation MSc The potential influence of feeding, ranging and social behaviours on the singing behaviour of the Bornean agile gibbon (Hylobates albibarbis (Hylobates albibarbis) 14052894 Lloyd MSc. Primate Conservation September 11th, 2015 1 Statement of originality 2 Abstract Gibbons are small, arboreal apes that sing to defend their territory and exclusive access to mates from same sex conspecifics. It is thought that singing is an energetically costly activity and is influenced by the energetic level of the singing animal. It is also thought that the song of the gibbon carries information about the strength of the pair bond; the relationship between the mated pair, to be displayed to other groups as a deterrent to territory invasions. I used focal time sampling to collect behavioural data on two groups of Bornean agile gibbons (Hylobates albibarbis) living in the Natural Laboratory of Peat Swamp Forest in the Sabangau Catchment, Central Kalimantan, Indonesia that related to social, feeding, ranging and territoriality. My intention was to use multiple regression and Spearman’s rank correlation to find evidence to refute or support the suggestion that differences in energy balance, social behaviours implicative of a strong pair bond and the occurrence of intergroup encounters influenced the level of singing behaviour. Difficulties encountered during the statistical analysis however meant that results were inconclusive with relation to energy balance and intergroup encounters. We did find some evidence however that behaviours associated with pair bond strength are not associated with changes in time spent singing, the time the gibbons began to sing, length of song bouts, number of great calls and group position in the morning chorus of gibbon calls, although a small sample size means these results should be considered with caution. If correct these results could imply that pair bond strength is not an important influence on singing behaviour. 3 Acknowledgements I would like to thank all of the staff at OuTrop for making me feel welcome, sharing their vast knowledge with me and introducing me to their beautiful forest. I would especially like to thank my supervisor Dr Susan Cheyne and the lead primate scientist at OuTrop Carolyn Thompson who have both provide me with wonderful advice and support, and every single individual who helped me collect data during my time at Outrop. I would also like to thank the wonderful people at Oxford Brookes University, both students and staff my family who supported me to the utmost of their abilities to make my dream of studying primates in Borneo a reality. 4 Table of Contents Title Page………………………………………………………….....1 Statement of Originality…………………………………………......2 Abstract………………………………………………………………3 Acknowledgements…………………………………………………..4 Table of Contents…………………………………………………….5 Lists of Appendices, Tables and Figures…………………………….8 Chapter 1: Introduction 1.1.1 The Hylobatidae……………………………….11 1.1.2 Taxonomy and Biogeography…………………13 1.1.3 Physical Description…………………………...16 1.1.4 Feeding and Ranging…………………………..14 1.1.5 Social Structure………………………………..17 1.1.6 Conservation……………………………….......22 1.2 Study Species…………………………………………….23 1.3 Singing in Gibbons………………………………....…….27 1.3.1 How gibbons sing………………………………27 1.3.2 The purpose of singing…………………………29 5 1.3.3 Influences on singing……………………………30 1.4 Objectives and hypotheses……………………………...…31 Chapter 2: Methods 2.1 Study area………………………………………………....34 2.2 Study groups………………………………………………37 2.3 Data collection…………………………………………….40 2.3.1 Locating and following the focal animals………40 2.3.2 Collecting singing data………………………….41 2.3.3 Collecting feeding data………………………….42 2.3.4 Collecting behavioural & ranging data………….42 2.4 Data Analysis……………………………………………...44 2.4.1 Sample size………………………………………44 2.4.2 Data analysis……………………………………..45 Chapter 3: Results 3.1 Multiple regression analysis……………………………….47 3.1.1 Proportion of time spent singing………………....48 3.1.2 Total time spent singing………………………….52 3.1.3 Time of first great call……………………………56 6 3.2 Spearman’s Rank Correlations…………………………….60 Chapter 4: Discussion 4.1 Statistical difficulties………………………………………65 4.2 The influence of energy balance and intake on singing behaviour………….................................................................................65 4.3 The influence of social behaviour on singing behaviour…...68 4.4 Methodological flaws……………………………………….69 Chapter 5: Concluding statement………………………………………..71 References………………………………………………………………..73 Appendix 1…………………………………………………………….....89 7 List of appendices, tables and figures Appendix 1: Ethogram of gibbon behaviours…………………………………………………………………………………89 Table 3.1.: Showing the results of a multiple regression on the proportion of time spent singing……………………………………………………………………………………48 Table 3.2.: Showing the results of a multiple regression on total time spent singing……………………………………………………………………………………52 Table 3.3.: Showing the results of a multiple regression on the time of first great call………………………………………………………………………………………..56 Table 3.4.: Showing the results of a Spearman’s rank correlation on abstinence from singing…………………………………………………………………………………....60 Table 3.5.: Showing the results of a Spearman’s rank correlation on time of first sing……………………………………………………………………………………….61 Table 3.6.: Showing the results of a Spearman’s rank correlation on order in the chorus…………………………………………………………………………………….61 Table 3.7.: Showing the results of a Spearman’s rank correlation on the total number of great calls……………………………………………………………………………………….62 Table 3.8.: Showing the results of a Spearman’s rank correlation on the average number of great calls per bout………………………………………………………………………..63 Table 3.9.: Showing the results of a Spearman’s rank correlation on average bout length……………………………………………………………………………………...64 8 Figure 1.1.: A distribution map of the Hylobatidae family across east Asia………………………………………………………………………………………..14 Figure 1.2.: The global range of the Bornean agile gibbon (Hylobates albibarbis)…………………………………………………………………………………25 Figure 2.1.: A map showing the National Laboratory of Peat Swamp Forest in Borneo……………………………………………………………………………………..35 Figure 2.2.: A map showing the transects in the National Laboratory of Peat Swamp Forest………………………………………………………………………………………37 Figure 2.3.: A map showing the gibbon territories in the National Laboratory of Peat Swamp Forest………………………………………………………………………………………39 Figure 3.1.: A scatterplot of the proportion of time spent singing compared with the time spent feeding on fruits……………………………………………………………………...49 Figure 3.2.: A scatterplot of the proportion of time spent singing compared with the proportion of time spent resting………………………………………………………........50 Figure 3.3.: A scatterplot of the proportion of time spent singing compared with the proportion of time spent playing……………………………………………………………51 Figure 3.4.: A scatter plot of the total amount of time spent singing compared with the time spent feeding……………………………………………………………………………..53 Figure 3.5.: A scatter plot of the total amount of time spent singing compared with the proportion of time spent resting………………………………………………………….54 9 Figure 3.6.: A scatter plot of the total amount of time spent singing compared with the average speed for that day………………………………………………………………..55 Figure 3.7.: A scatter plot of the time of first great call compared with the time feeding……………………………………………………………………………………57 Figure 3.8.: A scatter plot of the time of first great call compared with the proportion of time spent playing……………………………………………………………………………..58 List of abbreviations: -NLPSF - The National Laboratory of Peat Swamp Forests -OuTrop - The Orangutan Tropical Peatland Project -CIMTROP - The Center for International Cooperation Management of Tropical Peatland -GPNP - Gunung Palung National Park 10 Chapter 1: Introduction 1.1.1 The Hylobatidae The gibbons are the small, arboreal apes of the Hylobatidae family. While their precise taxonomy has undergone recent changes and is still disputed it is generally accepted that there are approximately 16 species of gibbon living across South East Asia (Blair, et al., 2011 Geissmann, 2007; www.iucnredlist.org, 2015; Thinh, et al., 2010). Possibly the most notable feature of gibbon behaviour is their propensity to produce loud, distinct songs which have been suggested to fulfil a number of functions, including territory defence, mate defence, mate attraction, intergroup spacing and the maintenance of the bond between mated individuals (Cowlishaw, 1996; Fan, et al., 2009a; Mitani, 1985; O’hagan, 2013). The influence that energy balance and intake might have on such features of the gibbons’ singing behaviour as the number, timing and length of song bouts has been briefly discussed by other authors (Bartlett, 1999; Fan, et al., 2008a). In this study on Bornean agile gibbons (Hylobates albibarbis) it was my intention to look at the potential influence of energy balance in further detail, examining such factors as the proportion of figs, leaves and fruit in the gibbon diet, as well as their daily path length and the proportion of time spent travelling. I looked at the potential influence that the relationship between the mated pair (represented by the proportion of social behaviours linked to pair bond strength in the activity budget) and encounters with neighbouring groups might have on singing behaviour. I intended to try and elucidate to what level and in what proportion with regards each other these factors influence gibbon singing behaviour. 11 Understanding the nature of