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THE UNIVERSITY OF CALGARY

The Feeding Ecology, Ranging Behaviour, and Activity Budget of Geoffroy’s Pied Colobus (Colobus vellerosus) at the Boabeng-Fiema Monkey Sanctuary

By Julie A. Teichroeb

A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFULLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS

DEPARTMENT OF ANTHROPOLOGY CALGARY, ALBERTA January, 2002

© Julie A. Teichroeb 2002


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THE UNIVERSITY OF CALGARY FACULTY OF GRADUATE STUDIES

The undersigned certify that they have read, and recommend to the Faculty of Graduate Studies for acceptance, a thesis entitled “The Feeding Ecology, Ranging Behaviour, and Activity Budget of Geoffroy’s Pied Colobus (Colobus vellerosus) at the Boabeng-Fiema Monkey Sanctuary” submitted by Julie A. Teichroeb in partial fulfillment of the requirements for the degree of Master o f Arts.

'r. J.D. Paterson, Department of Antliropology.

Dr. M.S.M. Pavelka, Department of AnthropMogy.

Dr. R.W. Lorfgair, Department o f Zoology.

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ABSTRACT

Recently, research has revealed that colobus diets and social systems are more varied than previously thought. This study presents a preliminary look at the behavioural ecology of a little known colobus species, Geofffoy’s Pied colobus (Colobus vellerosus). Two different sized groups (N=31-33 and N=7-8) were studied for four months at the Boabeng-Fiema Monkey Sanctuary in central Ghana. This period encompassed both a wet and a dry season. On 51 full-day follows during 551.25 hours of data collection, 2205 activity scans were collected using the frequency method. Ninety-one hours of detailed behavioural observations were collected via focal-animal sampling. A total of 55 plant species were fed upon and the bulk of the diet was made up of leaves (81.75%). Seasonal changes affected the diet; the dry season saw an increase in seed and floral bud consumption, and a decrease in leaf feeding. Within-group activity budgets were not affected by seasonality, however, between the groups, some differences appeared in the dry season. Group size also affected canopy use patterns; the large group was found to spend more time below the middle layer of the canopy than the small group. Ranging data showed that C. vellerosus at Boabeng-Fiema is experiencing scramble competition; in both the dry and wet seasons, the large group entered significantly more quadrats on a daily basis than the small group. The ‘pushing-forward’ effect was only found to drive this competition when one food item (out of seven tested) was fed upon. This suggests that competition is limited to certain food items or that a different mechanism drives scramble competition when other items are fed upon.

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ACKNOWLEDGEMENTS

All of the work that culminated into the writing of this thesis would not have been possible without the assistance of many people. Grateful thanks go out to my supervisor Dr. James D. Paterson, for his encouragement and support throughout the last few years. It is to him that I owe much of my academic growth. I would also like to gratefully acknowledge the assistance and guidance (not to mention field site) provided by Dr. Pascale Sicotte, without whom this research would not have been possible. My heartfelt thanks also go out to Tania Saj, whose motivation, work ethic, and courage kept me continually inspired throughout our long field experience. For taking time out of their busy schedules, sitting on my defense committees, and providing helpful comments I am grateful to Dr. Alan Smart, Dr. Pascale Sicotte, Dr. Mary Pavelka, and Dr. Rob Longair. I would also like to thank Myma Haglund, Jill Ogle, May Ives, and Tracy Wyman in the Department of Anthropology for aiding me in so many small and large ways. My work at Boabeng-Fiema Monkey Sanctuary would not have been possible without the support of the Ghana Wildlife Service, John Mason at the Nature Conservation Research Centre (NCRC) in Ghana, and the Management Committee at Boabeng-Fiema. I am indebted to Alfred and Bea Annov-Donyina for their constant help and advice, which made my integration into Ghanaian culture much easier. For their hard work in the field, I would like to thank Tony Dassah (Ghana Wildlife Service, BoabengFiema Monkey Sanctuary), Megan Bulloch, Moses Ampofo, and Sarah Wong. The Department of Botany, Herbarium at the University of Ghana at Legon provided aid in

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identifying plant species. As well, Kerry Larkin gave much needed help with map cosmetics. This research would not have been possible without funds provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Province of Alberta, and the University of Calgary’s Faculty of Graduate Studies, Department of Anthropology, and Research Services. Last but not least, all my love and appreciation goes out to my wonderful family and friends, who have shown unending belief in me. Especially, Susan, Herman, and Michael Teichroeb, Antonio Sorge, John Hamm, Kara and Scott Wilson, and Wilson Wong.

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TABLE OF CONTENTS

Approval Page........................... ii A bstract.................................................................................................................................iii Acknowledgments................................................................................................................ iv Table of Contents................................................................................................................ .vi List o f Tables.........................................................................................................................ix List o f Figures.........................................................................................................................x CHAPTER ONE: INTRODUCTION Introduction................................................................................................................ 1 Research Objectives.............................................................................................. 3 Research Questions................................................................................................... 4 Diet.............................................................................................................. 4 Activity Budget........................................................................................... 5 Ranging Behaviour...................................................................................... 5 Other Considerations................................................................................... 5 Thesis Overview.........................................................................................................6 CHAPTER TWO: LITERATURE REVIEW Introduction.............................................................................................................. 7 The Colobus Monkeys............................................................................................. 7 Taxonomy of Colobus vellerosus..................................................................9 The Feeding Ecology o f Black-and-White Colobus Monkeys...............................11 The Chemistry o f Feeding Preferences.................................................................... 16 Legumes and Soil Chemistry................................................................... 18 Black-and-White Colobus Social Structure............................................................ 20 Black-and-White Colobus Activity Budget............................................................ 24 Canopy U se................................................................................................ 25 Ranging Behaviour................................................................................ 26 Comparisons of the Diets of Neighbouring, Same-Species Groups......................29 Within Group Food Competition in the Primate Order..........................................31 Group Size................................................................................................................32 Group Size Effect on Ranging Behaviour.............................................. 35 Group Size Effect on Activity Budget.........................................................39 Group Size Effect on Canopy Use......................................................... 40 Group Size Effect on Feeding Behaviour...................................................40 Group Size Effect on Reproduction............................................................ 42 Formal Predictions............................................................................................... 43 Diet.......................................................................................................... 43 Activity Budget.......................................................................................... 44 Ranging Behaviour.................................................................................. 45

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CHAPTER THREE: SITE DESCRIPTION & METHODS Introduction.......................................................................................................... 46 The Boabeng-Fiema Monkey Sanctuary............................................................. 46 52 Study Subjects.................................................................................................. Methodology.......................................................................................................... 52 53 Frequency Method................................................................................. Focal-Animal Sampling...............................................................................55 Rainfall Data Collection..................................................................... 57 Phenology.................................................................................................. 58 Ecological Measurements......................................................................... 58 Data Analyses...................................................................................................... 59 CHAPTER FOUR: RESULTS Introduction.......................................................................................................... The Data Set............................................................................................... Feeding Behaviour.............................................................................................. Differences in Dietary Composition between the Groups............... Trees, Shrubs, and Lianes in the Diet.................................................... Seasonal Effects on Diet......................................................................... Activity Budget...................................................................................................... Comparison of Activity Budgets between the Groups....................... Sex Differences in Activity Budgets..................................................... Seasonal Effects on Activity Budgets...................................................... Canopy Use.......................................................................................... Ranging Behaviour............................................................................................... Comparison of Home Ranges between the Groups............................ Comparison of Day Ranges between the Groups.................................... Seasonal Effects on Home Ranges......................................................... Seasonal Effects on Day Ranges............................................................. Is the ‘Pushing-Forward’ Effect Driving Scramble Competition in C. vellerosus?........................................................................................ Is the Variation in Feeding Bout Durations due to the Type of Plant Part?............................................................................................. Important Timber Species as Food Trees.........................................................

62 62 63 64 69 69 72 73 74 74 76 78 78 80 81 83 83 86 86

CHAPTER FIVE: DISCUSSION & CONCLUSIONS Introduction.......................................................................................................... 89 Summary o f Diet Results...................................................................................... 89 Diet Comparison with other Black-and-White Colobus................... 90 Seasonal Variation in the Diet.................................................................. 94 Dietary Differences between the Study Groups...................................... 95 Scramble Competition for Food............................................................ 96 Timber Species in the Diet...........................................................................98 Summary o f Activity Budget Results................................................................. 98 Activity Budget Comparison with other Black-and-White Colobus... 99 Activity Budget Comparison between the Study Groups................... 100

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Canopy Use........................................................................................... 102 Summary of Ranging Behaviour Results......................................................... 102 Ranging Behaviour Comparison with other Black-and-White Colobus.. 103 Ranging Differences between the Study Groups................................ 104 Seasonal Effects on Ranging............................................................. 106 106 Limitations and Directions for Future Research............................................ Conclusions............................................................................................................. 107

REFERENCES..............................................................................................................

109

APPENDIX A: Behavioural Categories for Focal-Animal Sampling........................

125

APPENDIX B: List of Plant Families in the Diet......................................................... 128


LIST OF TABLES

Table 2.1: The Diets of Black-and-White Colobus Species(%)....................................

16

Table 2.2: Group Composition of Black-and-White Colobus species.............................. 22 Table 23 : Ranging Behaviour of Black-and-White Colobus......................................... 28

Table 3.1: Scan-sample Behavioural Categories............................................................. 54

Table 4.1: Frequency Method Data Obtained for the Large Group (WW).................... 63 Table 4.2: Frequency Method Data Obtained for the Small Group (G7)......................... 63 Table 4.3: Focal-Animal Data Obtained for Both Groups.............................................

63

Table 4.4: Total Diet for Both Groups from August to November................................

65

Table 4.5: Top Five Food Species Eaten by Each Group.................................................. 69 Table 4.6: Percentage of Records Spent Above, At, and Below the Middle o f the Canopy for WW and G7 Each Month................................................................... 77 Table 4.7: Differences between Female Feeding Bout Durations for Seven Plant Parts. 85 Table 4.8: Timber Classification of Important Food Trees at Boabeng-Fiema

88

Table 5.1: Comparison of the Diets of other Black-and-White Colobus Species with the Diet of Colobus vellerosus (%).............................................................

91

Table 5.2: Comparison of the Activity Budgets of other Black-and-White Colobus Species with that of Colobus vellerosus............................................................. 100 Table S3: Comparison of the Ranging Behaviour of C. vellerosus with that of other Black-and-White Colobus......................................................................... 103

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LIST OF FIGURES

Figure 2.1: The Presumed Dispersal Tracks of the Black-and-White Colobus Species...................................................................................................................... 9 Figure 2.2: Cladogram of the Inferred Relationships between the Five Black-andWhite Colobus Species......................................................................................... 11 Figure 2.3: Adult Female Colobus vellerosus at the Boabeng-Fiema Monkey Sanctuary.................................................................................................................. 11

Figure 3.1: The Location of the Boabeng-Fiema Monkey Sanctuary in Ghana...............47 Figure 3.2: The Major Vegetation Types at the Boabeng-Fiema MonkeySanctuary

49

Figure 4.1: Plant Parts Eaten by Both Groups................................................................. 67 Figure 4.2: Comparison of Plant Parts Eaten by Each Group........................................ 68 Figure 4.3: Rainfall over the Study Period...................................................................... 69 Figure 4.4: Dietary Changes for WW................................................................................ 70 Figure 4.5: Dietary Changes for G7................................................................................... 71 Figure 4.6: Overall Activity Budget for Both Groups..................................................... 72 Figure 4.7: Activity Budget Comparison of WW and G7.............................................. 73 Figure 4.8: Activity Budget Changes for WW from August to November................... 75 Figure 4.9: Activity Budget Changes for G7 from August to November.................... 75 Figure 4.10: Overall Canopy Use Patterns..................................................................... 77 Figure 4.11: The Total Ranges of WW and G7............................................................... 79 Figure 4.12: The Number of Quadrats Entered per Month by Each Group.....................80 Figure 4.13: WW’s Range During the Wet and Dry Seasons...........................................82

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1 CHAPTER 1

INTRODUCTION

An important first step in understanding any species is a general study of its behavioural ecology. This usually involves the detailed documentation of feeding patterns, movements, and daily activities. For many primate species, this basic information is still unknown. The African colobus monkeys are a group that has only recently begun to gamer much attention from researchers. As of 1990, only a few colobus species had been studied in detail in the wild (Procolobus badius: Struhsaker, 1975; P. verus: Oates, 1988; Colobus guereza: Oates, 1977a,b,c; 1978; Dunbar, 1987; C. satanas: McKey, 1978; McKey & Waterman, 1982; Harrison, 1986). More recently, research from various sites on the red and black-and-white colobus species have allowed a level o f comparison between study sites and species that was previously unavailable (P. badius: Siex & Struhsaker, 1998; C. polykomos: Dasilva, 1994; 1992; C. guereza: Fashing, 2001a,b,c; Bocian, 1997; C. satanas-. Fleury & Gautier-Hion, 1999; C. angolensis: Maisels etal., 1994; Bocian, 1997). Before this thesis, the only data available for Geoffroy’s pied colobus or the white-thighed colobus (Colobus vellerosus, Geoffroy, 1830) was collected by Olson and Curtin (1984) and Olson (1986) at Bia National Park in Ghana. Although they collected over 3000 hours of data, very little of this was published. The only available information comes from one abstract and one methodological paper (Olson & Curtin, 1984; Olson, 1986).


This thesis attempts to fill in some of the knowledge gaps for C. vellerosus in regards to its general behavioural ecology. A description of the diets, activity budgets, and ranging behaviour of two neighbouring, differently sized groups during a wet and dry period is provided. A comparison of the diets of two groups within the same habitat has rarely been quantified; only a few studies have been designed to investigate food choice for same-species groups with similar resource availability (Colobus guereza: Fashing, 2001b; Grimes, 2000; Procolobus badius: Chapman & Chapman, 1999; Cebus capuchinus: Chapman & Fedigan, 1990; Cercocebus albigena: Waser, 1977). However, these differences are important in understanding the study species’ dietary variability, habitat food availability, and the degree to which they can utilize these resources. Studies o f this nature also have the added benefit of controlling for observer, methodological, phylogenetic, and certain ecological differences between the compared groups (Chapman & Chapman, 1999). A comparison of two widely varying group sizes of the same colobus species is also interesting in light of recent theorizing. In the primate literature, much debate reigns over why the same species will often form such differently sized groups (Janson & Goldsmith, 1995; Crockett & Janson, 2900; Chapman & Chapman, 2000). These have been found to vary up to five times in certain species (Dunbar, 1988). Generally, it is thought that animals form groups for several reasons, including predation avoidance, increases in foraging efficiency, and protection from conspecifics but the upper limit on group size is set by increasing food competition (Alexander, 1974; van Schaik, 1983; Wrangham et ah, 1993; Crockett & Janson, 2000). Thus, diet, food availability, and the intensity of food competition for a species should predict the size of its groups. In


folivores, who theoretically experience little food competition because leaves are abundant and of low quality, large groups are expected to form so that the potential benefits are maximized. However, most folivores form smaller groups than expected. Steenbeek and van Schaik (2001) have called this the ‘folivore paradox’. Consequently, it has been theorized that factors other than food competition are limiting group size in folivorous primates. Some researchers believe that the social stress and increased infanticide risk seen in larger colobine groups may explain the formation of smaller groups (Yeager & Kirkpatrick, 1999; Crockett & Janson, 2000; Steenbeek & van Schaik, 2001). In female-transfer species, females may be able to directly control group size in a way that females in male-transfer species can not. Thus, in some colobines, females may react directly to the threat of infanticide or increased food competition by transferring to another group, keeping overall group size small (Crockett & Janson, 2000). This thesis will not directly measure the factors that limit group size in C. vellerosus, however the results lend support to the conclusion that at least one type of within group food competition is being experienced and the behavioural mechanism driving this competition will be investigated.

I. Research Objectives This thesis describes three aspects of the behavioural ecology o f Geoffrey’s pied colobus at the Boabeng-Fiema Monkey Sanctuary (BFMS) in central Ghana. During a four-month study (August - November 2000), diets, ranging behaviour, and activity budgets were recorded for two groups of varying sizes (N=31-33 and N=7-8). Due to the size difference of the two study groups and because data was collected during the short


wet season and at the beginning of the long dry season, the effects of group size and seasonal changes on diet, ranging, and activity budget were investigated. It is assumed that individuals in two groups of such different sizes will be faced with different challenges in acquiring food (van Schaik et al., 1983). As well, the phenological changes in the vegetation caused by seasonality are expected to affect the diet and perhaps the activity budget and ranging of both groups (Lieberman, 1982). The differential use of tree and liane species as food sources is investigated because this may show how the habitat is being used and illustrate differences between C. vellerosus and other black-andwhite colobus. As well, the canopy use patterns of the two groups were examined because these have been found to vary for different sized wedge-capped capuchin groups (de Ruiter, 1986). The results of these analyses led to several questions about the within group food competition experienced by C. vellerosus. These are also investigated, along with the importance o f timber species in the diet at BFMS, which may prove useful when planning future conservation initiatives. Research Questions; During the course of this study, the following research questions in four areas were investigated in detail: Diet 1. What plant species and plant parts make up the diet of C. vellerosus at BFMS? 2. How similar is the diet of C. vellerosus to other black-and-white colobus species? 3. Are lianes or tree species favoured? 4. What are the dietary differences between the groups?


5. How does the diet of C. vellerosus alter with changes in rainfall? 6. To what extent can dietary differences be explained by food availability? Activity Budget 7. How do groups of C. vellerosus spend their time? 8. Does activity budget differ for the two differently sized study groups? 9. Do changes in rainfall affect activity budgets? 10. Do canopy use patterns differ between the groups? Ranging Behaviour 11. How far do groups of C. vellerosus range? 12. Does group size affect the length of day journeys? 13. Does group size affect home-range size? 14. Do home-range use patterns change with seasonality? 15. Are day ranges affected by seasonality? Other Considerations 16. Is within group scramble competition for food being experienced by C. vellerosus at BFMS? 17. Is the ‘pushing-forward’ effect the mechanism driving this competition? 18. Does feeding on different plant parts change the duration of feeding bouts? 19. How important are economically used timber species in the diet of C. vellerosus at BFMS?


II. Thesis Overview This thesis investigates the behavioural ecology of two differently sized groups of Colobus vellerosus. Chapter One is a brief introduction to the thesis topic and research objectives. In Chapter Two, the literature available on the feeding ecology, social structure, activity budget, and ranging behaviour of the five black-and-white colobus species is reviewed. As well, studies dealing with comparisons of same-species groups of different sizes are analyzed. Finally, this chapter provides the formal predictions that were made before fieldwork was undertaken. In Chapter Three a description of the study site is provided and the methods used for data collection and analyses are described. Chapter Four presents the results of this study in three broad categories: feeding ecology, activity budget, and ranging behaviour. Questions that arise from these results are also investigated. In Chapter Five, the results are discussed with reference to the available literature on other black-and-white colobus species and to the predictions outlined in Chapter Two. At the end, the conclusions o f this study are presented and directions for future research are put forth.


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CHAPTER 2

LITERATURE REVIEW

Introduction This chapter provides an overview o f the literature relevant to this thesis. The available data on Colobus vellerosus is reviewed and to supplement this scant information, a review of the feeding, social, and ranging behaviour of other black-andwhite colobus is provided. The feeding ecology of this taxon will be summarized with special emphasis placed on seasonal changes in diet and behaviour. A brief review of previous studies o f the diets of neighbouring groups of the same species will be provided. As well, the types of food competition displayed by primates are described. A review of the literature detailing group size effects on the behaviour of same-species groups will also be analyzed. The end of this section is summarized with fourteen formal predictions.

I. The Colobus Monkeys Colobine monkeys inhabit Africa and Asia and are broken into two distinct groups, the Asian langurs and the African colobus monkeys (composed of five species of black-and-white colobus: Colobus guereza, C. polykomos, C. angolensis, C. satanas, and C. vellerosus; four species of red colobus: Procolobus badius, P. pennantii, P. preussi, and P. rufomitratus, and one species of olive colobus, Procolobus verus) (Rowe, 1996). African fossil colobines from the Miocene are distinctive but poorly known and unlike cercopithecines, the extinct colobine taxa have yet to be linked to living forms. Delson


(1994) states that “colobines underwent ‘adaptive radiations’ in Europe and Africa, producing a variety o f distinctive species that died out, to be replaced by collateral relatives that survive today.” Pp. 41. Grubb (1982) has hypothesized that the five present day black-and-white colobus species developed during several cycles of climatic change during the Quaternary. In the last 1.7 million years, 17 glacial and interglacial sequences in Europe (one approximately every 10,000 years) affected climates in the lower latitudes. In Africa, these have proven difficult to date but seem to have caused climatic cycles where warm, moist periods fluctuated with cooler, dry periods (Livingstone, 1975). The original black-and-white colobus species seems to have been Colobus angolensis, whose range expanded during a wet period of extended forest cover from the center of the continent to West Africa (Figure 2.1). Then during a dry period, a part of the population in Upper Guinea was isolated and C. polykomos evolved. Later, during another period o f forest expansion, this population extended eastward, through the Benue valley across Africa to Ethiopia and eastern Africa. The Dahomey gap separated these two populations and at this time C. guereza appeared. C. vellerosus may have developed with this eastward expansion of C. polykomos or it is possible that they developed during a more recent dry period when the Baoule-V (a strip of savanna dividing the Upper Guinea forest block in Cote d’Ivoire) is thought to have extended all the way to the coast (Booth, 1958; Martin, 1991). The origin of the black colobus (C. satanas) is unclear. Grubb (1982) has hypothesized that they may have existed earlier in the “West Central” area o f endemism that C. angolensis came from. They may be the most primitive form of black-and-white colobus because the neonate is brown, rather than white (Oates et al, 1994).


9

g u ereza

polykomos

p. vellerosus sa tan a s,

an g o len sis

Figure 2.1: The Presumed Dispersal Tracks of the Black-and-White Colobus Species (Arrows link ancestral and derivative species. Areas o f sympatry are hatched. From: Grubb, 1982) The colobines developed a sacculated stomach with a ruminant-like digestion pattern that allows them to take advantage of a herbivorous and usually arboreal niche (Hladik, 1978). Colonies of bacterial flora in their foregut enable them to break down the cellulose and hemicelluloses in plant cell walls allowing them to take advantage of mature leaves as a food source (Milton, 1984). Colobines also produce copious amounts o f saliva, which is thought to buffer the acid in the forestomach fluid, keeping the pH at acceptable levels for the bacterial microflora that aids in digestion (Waterman & Kool, 1994). They are ‘anatomical folivores’ and differ from ‘behavioural folivores’, such as howler monkeys (Allouatta sp.), who lack these specific digestive adaptations and whose leaf-feeding is comprised almost exclusively of young leaves (Milton, 1978). Taxonomy o f Colobus vellerosus Before 1927, there were thought to be two distinct western black-and-white colobus species, C. polykomos in the far west (Sierra Leone, Liberia, Guinea, Ivory Coast) and C. vellerosus on the Gold coast (Ghana and Togo). The former (C. polykomos), have long, grey-white hair fringing the face and head crown, extending back


10 to the shoulders, where it forms long “epaulettes”. The latter (C. vellerosus), have a bushy, pure or creamy white facial fringe, which is restricted to the circumfacial region, no epaulettes, and no white crown (as well as a white stripe on the thigh that develops gradually as individuals mature) (Groves et al., 1993) (see Figure 2.3). However, in 1927 the discovery of a form o f black-and-white colobus which seemed intermediate between these forms (C. polykomos dollmani) in Cote d’Ivoire (between the Bandama and Sassandra rivers) led to C. polykomos and C. vellerosus being grouped into one species (C. polykomos), which was assumed to show great subspecific variation (Groves et ah, 1993). In 1983, in an analysis of variation in male loud calls in black-and-white colobus, Oates and Trocco found evidence that challenged this grouping. They found that C. vellerosus' loud calls are more similar to the East African form, C. guereza, than they are to C. polykomos. They also noted some pelage similarities between C. guereza and C. vellerosus. This loud call analysis was reevaluated with more data in 2000 by Oates et ah with the same results. Both Oates and Trocco (1983) and Oates et al. (2000) came to the conclusion that C. vellerosus is indeed a distinct (more derived) species from C. polykomos, closely related to C. guereza (Figure 2.2). Further evidence from a comparison of features of the skulls and skins of C. polykomos, C. vellerosus, and C. p. dollmani led Groves et al. (1993) to support the status of C. vellerosus as a separate species. (Groves et al. (1993) and Oates and Trocco (1983) agree that C. p. dollmani is so variable that it represents a hybrid between C. polykomos and C. vellerosus, and not a true subspecies.) The understanding that C. vellerosus is a separate species quickly led to the realization that this species is endangered and among the least studied of all colobine species.


11

E “

C. guereza C. vellerosus C. polykomos

"

C. angolensis

— — — — —

—

C. satanas

Figure 2.2: Cladogram of the Inferred Relationships between the Five Black-andWhite Colobus Species. From: Oates et al., 2000.

Figure 2.3: Adult Female Colobus vellerosus at the Boabeng-Fiema Monkey Sanctuary. Photo by: J.A. Teichroeb

II. The Feeding Ecology of Black-and-White Colobus Monkeys Colobus vellerosus is classified as an arboreal folivore and is found in lowlandmoist and semi-dry deciduous gallery forests in Ghana and Togo (Oates et al., 1994). Up to this point, the limited information on the diet of C. vellerosus has suggested that young leaves, mature leaves, fruit pulp, and seeds are all important dietary items. Seasonal differences have been found in diet and ranging patterns. During the dry season, C.


12 vellerosus ate more fruit and seeds and used a smaller portion o f the home-range, than in the wet season (Oates, 1994). Overall, Olson and Curtin (1984) found that C. vellerosus use 120 species of plants at Bia, of which 91 (76%) were tree species. They showed that 25% of C. vellerosus ’ favored food species are economically important timber species in Ghana (especially a mahogany, Entandrophragma utile and the wawa tree, Triplochiton scleroxylon) (Abbiw, 1990). As a consequence of the lack of data on C. vellerosus, diet studies of the other black-and-white colobus species will be reviewed, beginning with the two most closely related (according to Oates and Trocco (1983)), C. polykomos and C. guereza. For the western black-and-white colobus (C. polykomos) in Tiwai, Sierra Leone, Dasilva (1994) found that the three main components of the diet were fruit and seeds (34.6%), young leaves (29.7%), and mature leaves (26.4%). The most commonly recorded food item was the unripe seeds of Pentaclethra macrophylla, which accounted for 37% of all seed and fruit feeding records. Dasilva (1994) also saw C. polykomos consume flowers, buds, pith, bark, and whole twigs. In contrast to C. vellerosus, liane species were preferred over tree species (-70% o f the diet) (Olson & Curtin, 1984). There were marked seasonal differences in the diet. Almost all records of fruit and seed eating fell in the dry season, immature liane leaves were most important in the dry-wet transition season and early wet season, and mature liane leaves were eaten most during the mid-wet season. Using phenological data, Dasilva (1994) noted that fruit or their seeds were preferred and heavily exploited whenever they were available, while mature leaves were consumed most when fruit and seeds were unavailable.


13 Oates (1977a) found a different dietary pattern for C. guereza in the Kibale Forest in East Africa Overall, leaves were more important in the diet of C. guereza than C. polykomos, with young leaves making up 57.7% of the diet, mature leaves 12.4%, and fruits 13.6%. Seeds were never heavily exploited. Oates (1977a) also observed feeding on flowers, buds, wood, bark, water plants, stems, petioles, and lichens. Like C. vellerosus, C. guereza utilized tree species more heavily than lianes (Olson & Curtin, 1984). Seasonality was not as marked in their diet, but the consumption of some favoured food species varied with wet season availability. Recent research at the Kakamega Forest in Kenya has shown that all C. guereza may not be folivorous to the same extent. For two groups at Kakamega, Fashing (1999; 2001b) found that fruit made up 44% and 33% of the annual diet and fruit consumption was significantly positively correlated with monthly fruit availability. In fact, fruit seemed to be the preferred food source for guerezas at Kakamega. It was eaten in proportion to its abundance and leaves were eaten most when fruit was not available. Unlike Oates’ (1977a) study, young leaves were not eaten in proportion to their abundance. Thus, diet in C. guereza may be heavily affected by factors within the habitat. Fashing (2001b) suggests that the abundance of fruiting trees in the Moraceae family at Kakamega may be causing the high level of frugivory at this site. Black colobus monkeys (C. satanas) are more like C. polykomos in their dietary patterns. McKey et al. (1981) showed that in Cameroon at the Douala-Edea Reserve, this species consumes the smallest amount of leaves compared to other black-and-white colobus (mature leaves 18.1%; young leaves 19.7%). However, mature leaves constituted almost 50% of leaf-feeding records, in contrast to C. guereza where mature


14 leaves made up only 18% of leaf-feeding records (McKey, 1978; Oates, 1977a). Once again, this trait is more similar to C. polykomos (Dasilva, 1994). Despite the fact that they ate more mature leaves, McKey et al. (1981) state that black colobus favoured young leaves, and mature leaves were eaten when no young leaves or seeds were present. Black colobus also consume the largest proportion of seeds compared with other blackand-white colobus species. Over half of the annual diet is made up of seeds (53.2%) and they seem to be destroyed and digested rather than dispersed (McKey, 1978). Seasonal changes greatly affected the diet. At the height of the rainy season, the diet was less diverse, mature leaves forming a large part o f feeding records because seeds and young leaves were rare (McKey, 1978). Seeds were fed upon heavily when they were available and at other times a mixture of seeds, young, and mature leaves made up the diet. The monkeys also fed on more lianes and saplings in the rainy season, presumably to increase the variation of leaves in the diet. Flowers and floral buds made up 3.3% of the diet and leaf buds made up 0.8%. Black colobus fed on a large number of different plant species (84) but avoided the mature leaves of all of the most common trees in the reserve, concentrating their feeding on more rare plants (this may be related to leaf and soil chemistry, see below). Differing from C. polykomos but like C. vellerosus and C. guereza, trees were more important food species than lianes, which made up 22.5% of leaf-feeding records. The Angolan colobus (C. angolensis) was studied in the early 1990’s in Salonga National Park in the Democratic Republic of the Congo (formerly Zaire) (Maisels et al., 1994). This 8-month study found that C. angolensis fed on 46 different plant species. They were similar to black colobus, feeding mostly on seeds (50%). The remainder of


15 their diet was made up of young leaves (21%), mature leaves (6.4%), fleshy fruit (16.8%), and flowers (5.9%). There was seasonal variation in their diet, seeds were important in months with 30 m) with many openings and no graminoids in the understory. Closed woodland is differentiated by a closed, low canopy with few tall trees (most 40 cm DBH) relative to the trails was measured for the map we carried out a sequence, measuring diameter at breast height (DBH), crown diameter, crown shape, and height. The diameter at breast height was measured using a DBH tape that automatically converted the circumference measurement


to a diameter. In the case of large buttresses, the relative widths of the buttresses were removed from the over-all measurement giving an estimation of the DBH. Crown diameter was estimated by laying a measuring tape across the forest floor parallel to the estimated end of the crown on each side. This was consistently done where the crown spread was the widest. Crown shape was estimated to be spherical or hemispherical to give a better assessment o f the available leaf matter. Tree heights were measured using a clinometer and trigonometry.

IV. Data Analyses The diet o f both groups was ascertained using data collected by the frequency method. Dietary intake was considered to be equal to the proportion of all of the records within the scan-samples in which an item was fed upon (which is equivalent to the time spent feeding on that item) (Davies et al., 1999). This yielded a percentage of the diet for each food type and these are compared between the groups. Activity budgets were assessed using the frequency method data. Ratios of the total number o f records for each behaviour over the total number of records were turned into a percentage for a representation of the total activity budget. For statistical comparisons, the proportion of scans for each behavioural category for each group and each age-sex class were compared using two-tailed Wilcoxon Mann-Whitney U tests. Raw scan frequencies could not be used because it was necessary to correct for group size differences and the fact that there are more females than males in both groups. Therefore, the day was the unit of analysis and the daily ratios listed below were compared in the Wilcoxon Mann-Whitney U tests. Due to the fact that both seasonal and


60 group comparisons had to be done using the same ratios, a Bonferroni Procedure was done to lower the alpha levels after these tests (Siegel & Castellan, 1988). Daily ratio fo r seasonal and group comparisons: = The number of records of that age/sex class involved in that activity that day The total number of individuals in that group recorded in that activity that day Daily ratio fo r sex comparisons: = The number o f records of that aee/sex class involved in that activity that dav The total number of records for that age/sex class that day

Canopy use was analyzed using the proportion of scans that each group spent at each level of the canopy per month. Comparisons between the groups were completed using two-tailed Wilcoxon Mann-Whitney U tests. The ranging behaviour was also assessed using the frequency method. Differences in day-ranges between the groups were ascertained by comparing the number of 50 x 50 m quadrats that each group entered on all full-day follows using a two-tailed Wilcoxon Mann-Whitney U test. A comparison of the total home-ranges was done using a Chi-square test. The total number of quadrats entered by each group were used as the observed values with an equal number used as the expected values. The durations of female feeding bouts, which were collected by focal-animal sampling, are used to find out if the ‘pushing-forward’ effect is driving scramble competition in Colobus vellerosus. For the two groups, these were compared for seven different plant parts using two-tailed Wilcoxon Mann-Whitney U tests. A final KruskallWallis test was performed to see if the variation in female feeding bout durations between the groups was due to the handling time of the plant part being consumed.


61 The statistical tests that were done during data analyses were done both by hand and with Statview 4.01, a statistical program for Macintosh computers.


62

CHAPTER 4

RESULTS

Introduction This chapter provides an overview of the major findings of this study in three broad categories: feeding behaviour, activity budget, and ranging. These results bring up two questions that are investigated further: 1) Is the ‘pushing-forward’ effect driving scramble competition in Colobus vellerosus?; and 2) What important food species are also important timber exports in Ghana? The Data Set The diet, activity budget, and ranging behaviour were all ascertained using the frequency method. The distribution of scans and records collected over the four-month study period for each group are listed in Tables 4.1 and 4.2. Each group was followed for an equal number o f hours, however the small group (G7) was less habituated than the large group (WW) at the beginning of the study so we obtained fewer scans of them in the first two months. The smaller number of monkeys in G7 accounts for the lower number of records acquired for that group when compared with WW. Data gathered by focal-animal sampling was used to ascertain the mechanism driving food competition in C. vellerosus. Table 4.3 summarizes the total focal-animal data. Samples were collected in order to represent the number of animals and the age-sex class make up within each group. Therefore, there are approximately twice the number o f focals for the large group and similarly for females when compared to males. In the


63 final data set, the samples on infants were not used and sub-adults were pooled with adults because a distinction was often difficult to make. Table 4.1: Frequency Method Data Obtained for the Large Group (WW) Other Month # # Move Feed Rest Social Scans Records Records Records Days Records Records 362 12 Aug. 7 292 850 168 42 314 11 283 823 178 58 Sept. 7 Oct. 282 301 842 9 6 168 33 Nov. 282 306 155 3 6 809 68 1139 1283 Total 26 3324 201 35 669

Total Records 1434 1384 1353 1341 5512

Table 4.2: Frequency Method Data Obtained for the Small Group (G7) Month # # Feed Rest Move Other Social Days Scans Records Records Records Records Records Aug. 7 268 134 532 97 0 0 Sept. 220 6 233 492 5 119 10 284 Oct. 232 6 507 155 34 8 Nov. 6 281 300 637 4 160 20 Total 25 1066 886 17 2168 531 64

Total Records 763 846 936 1121 3666

Table 4.3; Focal-Animal Data Obtained for Both Groups # Focals Age-Sex Class WW G7 Adult Males 108 49 Adult Females 222 79 Sub-Adult Males 16 5 Sub-Adult Females 30 27 Infants 10 0 Total # Focals 386 160 Total # Hours 64.3 26.7

# Hours 26.2 50.2 3.5 9.5 1.7 -

91

I. Feeding Behaviour Overall, 1283 feeding records were obtained for WW and 886 were obtained for G7 using the frequency method. From this total of 2169 feeding records, the diet was determined. A total o f 55 plant species were fed upon from 21 plant families (Appendix B). The large group fed on 48 species and the small group on 29. The combined diet for


64 both groups, broken down by plant species and plant part is provided in Table 4.4. It proved very difficult to see if animals were eating young or mature leaves from certain plant species, so I have listed a general ‘leaves’ category, with the ‘mature leaves’ and ‘young leaves’ categories, for cases when these could not be identified. The number of records where the plant species was unidentified was 156, or 7% of the feeding records. The overall plant part diet for WW and G7 combined is shown in Figure 4.1. For both groups, leaves were the most important food source. A total o f 81.75% of feeding records showed the animals feeding on leaves. In 8.75% of these records, the leaves were identified as mature and in 9.25% they were identified as young leaves. The next most important plant part was seed pods, which made up 7.5% of the feeding records. The remainder of the diet consisted of floral buds (4.5%), fruit (4%), soil (1%), leaf petioles (

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