Fruit-frugivore interactions in a Malagasy littoral forest - Universiteit ...

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Pteropus rufus Marshall (1983). Occasionally some seeds (up to 15mm length) are swallowed as well. For all three Uapaca sp., with seed length over 9.6mm, seeds were often swallowed but this is probably due to the pulp texture and slippery seeds. The threshold for swallowing seeds is reported as being less than 3.2mm diameter for a 600g Pteropus sp. and between 3–5mm for flying foxes in general (Corlett 1998; Shilton et al. 1999), which is smaller than the 10mm recorded at our study site. Our analyses showed no particular fruit mass preference. The fact that Pteropus spp. may transport fruits of over 200g (Marshall 1983) means that they are probably not limited by masses up to 50g, being the maximum fruit mass that was scored. ‘Bat fruits’ According to Fleming (1979), Marshall (1983), Stashko and Dinerstein (1988), Thomas (1988) and Korine et al. (1998) ‘bat fruits’ can be morphologically characterised as variable in size with a green or dull colour, a strong and musty odour, high water content, pendant position or held away from the foliage. This description corresponds with our results meaning that the flying foxes’ food species in Sainte Luce include fruits of all size, having no particular conspicuous colour, a strong odour and high water content. However, compared to the overall database of available fruits in this forest several of these variables are simply characteristic for the majority of fruits. Thus real food selection or clear preference cannot be established. Therefore it is important that future studies also focus more on all available food resources in an ecosystem rather than studying the diet of the bat species only. This way it will be possible to draw broader conclusions on real food preferences and typical ‘bat fruits’ compared to the wide array of fruits available. The exclusive role of flying foxes in seed dispersal Quantitatively important short and long distance seed dispersal Pteropus rufus feeds on a huge variety of fruits, which makes this species potentially an important seed disperser for a large number and diverse set of endemic plant species in the littoral forest. Compared to other frugivores in the littoral forest it is the only one capable of long distance seed dispersal since foraging may occur up to 50km away from the roost site (Thomas, 1988) thereby bridging isolated forest fragments. This ensures genetic exchange between plant populations of different forest fragments, and for very small fragments no longer inhabited by other mammal seed dispersers, only flying foxes can disperse these fruits. Long distance seed dispersal happens mainly between successive feeding trees (0.3–8.3km apart) or even further away between foraging areas and roost sites (up to 50km apart) for all ingested seeds (Morrison 1978; Korine et al. 1999). Gut passage rate in flying foxes is often only about 30 minutes (Morrison 1980), although there is also evidence for gut retention of food for large periods (>12h or >18h) in Pteropodidae (Shilton et al. 1999), which increases the possibility for long distance seed dispersal. As digestion can be rapid, large quantities of food can be processed every night. This is necessary because being flying mammals, these flying foxes have rather high-energy requirements and may eat at least the equivalent of their own body mass each night (Marshall 1983; Shilton et al. 1999). In addition, they are very numerous in the area. All this probably leads to a massive consumption of fruits and possible dispersal of seeds every night by a large number of animals. 99
Chapter 3a Germination experiments Izhaki et al. (1995) noted a positive effect of passage through bats’ guts on germination rate of the ingested seeds. Nevertheless, Palmeirim et al. (1989), Kalko et al. (1996), Iudica and Bonaccorso (1997), Korine et al. (1998), Shilton et al. (1999) as well as this study did not find such a relation. There seemed to be no positive or negative impact on germination rate and germination percentage of defecated seeds. The results on percentage of plants that finally germinated after 6 months are difficult to interpret and appear very variable. More extensive experiments under more controlled ecological conditions and with more replicas should be carried out to confirm these first preliminary data. But, even if germination itself does not profit from the digestive process, more important to consider is the distance covered by the flying foxes during gut passage. Threats and conservation options Unfortunately in Sainte Luce not only the fragmented habitat is at risk, but its inhabitants among which the flying foxes, are seriously threatened as well. During our field research the whole colony moved once from their original roost site to another one, five kilometers west, where they remained from February through May 2000. Afterwards the colony returned to the first roost site. At both roost sites, rocks, long sticks and injured patagia were indications of severe hunting pressure. Several bush fires in the nearby area perturbed the colony even more. Too much harassment might cause the colony to divide into smaller groups, and settle elsewhere, leaving the littoral forest deprived of its only capable long distance seed disperser. ACKNOWLEDGEMENTS We would like to acknowledge QMM (QIT Madagascar Minerals) for providing logistics and infrastructure at the campsite. In particular we thank Manon Vincelette, Jean-Baptiste Ramanamanjato, Laurent Randrihasipara of the QMM Environmental and Conservation Team and Prof. Dr. Jörg Ganzhorn (University of Hamburg) for their support in this research. We are very grateful to Dr. Johny Rabenantoandro of Missouri Botanical Garden (Antananarivo) for assistance with the identification of the plant species. We also thank Prof. Paul A. Racey (Univ. Aberdeen) for providing important literature and for his extensive revisions and useful suggestions. Finally we owe great thanks to Giuseppe Donati and the Malagasy assistants in the Sainte Luce campsite, without them this research would have been a lot harder. This study was carried out under a Collaboration Agreement between Department of Animal Biology and Department of Anthropology of the University of Antananarivo and the Institute of Zoology of Hamburg University and QMM. First author is supported by a Research Assistantship of the Belgian Fund for Scientific Research, Flanders (FWO). We thank the Flemish Government for structural support to the CRC of the RZSA. 100
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Fruit-frugivore interactions in a M
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Cover photographs: Front: Back: -
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Table of contents III. General conc
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Acknowledgements A special word of
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PREFACE Preface This work brings to
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General introduction Finally, seed
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General introduction high as 98% fo
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’Hazo tokana tsy mba ala’ One t
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Chapter 1 changes in resource avail
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Chapter 1 For analyses we narrowed
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Chapter 1 Fig. 2. Seasonal variatio
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Chapter 1 80 70 60 50 40 30 20 10 0
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Chapter 1 Fig 4. Comparison of data
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Chapter 1 Table 4. Data on phenolog
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Chapter 1 Relation with abiotic fac
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Chapter 1 Malagasy rainforests disp
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Chapter 1 Appendix I Continued Fami
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Chapter 1 Appendix I Continued Fami
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Malagasy proverb Drawing © Giusepp
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Chapter 2 the successful establishm
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Chapter 2 40 Table 1. The frugivore
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Chapter 2 Statistical analyses To v
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Chapter 2 Overall fruit trap data d
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Chapter 2 Table 3. Morphological an
Page 53 and 54: Chapter 2 depressed seeds (Fig. 3a)
Page 55 and 56: Chapter 2 Fig. 3. Ordination plot o
Page 57 and 58: Chapter 2 On a community level the
Page 59 and 60: Chapter 2 Appendix II. Plant-animal
Page 63 and 64: Malagasy proverb Lemur drawing © S
Page 65 and 66: Chapter 3 different consumer specie
Page 67 and 68: Chapter 3 Bollen et al. in press, C
Page 69 and 70: Chapter 3 64 Body 1,2 Body lenght (
Page 71 and 72: Chapter 3 dominant plant families s
Page 73 and 74: Chapter 3 Table 4. Morphological an
Page 75 and 76: Chapter 3 Table 4 Continued Paramet
Page 77 and 78: Chapter 3 Besides testing feeding s
Page 79 and 80: Chapter 3 and do not consume the fi
Page 81 and 82: Chapter 3 (1997) already pointed ou
Page 83 and 84: Chapter 3 1989; Galetti 1993; Saini
Page 85 and 86: Chapter 3 Appendix I. All plant spe
Page 87 and 88: Chapter 3 Other SD Hss Rats Rr Ew 8
Page 90 and 91: Pteropus rufus Feeding ecology of P
Page 92 and 93: Pteropus rufus number per species a
Page 94 and 95: Pteropus rufus Table 1 Continued Fr
Page 96 and 97: Pteropus rufus larger number of spe
Page 98 and 99: Table 2 Continued Number of seeds/d
Page 100 and 101: Pteropus rufus Food selection: expl
Page 102 and 103: Pteropus rufus presence. On the oth
Page 106 and 107: Coracopsis nigra The feeding ecolog
Page 108 and 109: Coracopsis nigra fruit pulp (70%) b
Page 110 and 111: Coracopsis nigra Table 1 Continued
Page 112 and 113: Coracopsis nigra Table 2. Morpholog
Page 115 and 116: Malagasy proverb Drawing of fruits
Page 117 and 118: Chapter 4 Most seed dispersal studi
Page 119 and 120: Chapter 4 Mean temperature is aroun
Page 121 and 122: Chapter 4 Number of seeds: 1-2, 3-1
Page 123 and 124: Chapter 4 Fig. 2. Monthly fruit ava
Page 125 and 126: Chapter 4 120 Table 3. Soil charact
Page 127 and 128: Chapter 4 Table 4. Morphological ch
Page 129 and 130: Chapter 4 Table 5. Biochemical char
Page 131 and 132: Chapter 4 Chemistry At both sites,
Page 133 and 134: Chapter 4 considering species numbe
Page 137 and 138: ’Ny valala tsy indroa mandry eo a
Page 139 and 140: Chapter 5 environmental degradation
Page 141 and 142: Chapter 5 at a very low density in
Page 143 and 144: Chapter 5 Table 1. A list of plant
Page 145 and 146: Chapter 5 (Ganzhorn et al. 1999a).
Page 147 and 148: Chapter 5 Animals The degree of vul
Page 149 and 150: Chapter 5 comm.). Mixed species pla
Page 151 and 152: Chapter 5 data are needed we believ
Page 153 and 154: General conclusion as in other site
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General conclusion selection pressu
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General conclusion are consumed by
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Samenvatting omstandigheden zijn bo
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Samenvatting vruchtkenmerken. Beide
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Samenvatting zaadverspreiding moete
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Résumé température et précipita
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Résumé (Sud-est de Madagascar) et
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Résumé des frugivores sur l’év
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References Bollen A, Van Elsacker L
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References Dowsett JR (2000) Le sta
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References Godfrey LR, Junger WL, R
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References Janson CH, Chapman CA (1
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References Marshall AG (1983) Bats,
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References Rabevohitra R, Lowry PP,
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References Tattersall I (1982) The
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family Loganiaceae scientific name
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