Abstract
Fleshy-fruited plants and frugivores share a mutualistic relationship with plants offering the frugivores a reward of fleshy fruit pulp in order to disperse their seeds. However, all fruits are not equal in terms of energy available to frugivores. Consequently, we measured the assimilation efficiencies of fruits of six indigenous tree species for an avian frugivore, the Knysna Turaco (Tauraco corythaix). We predicted that the Turacos would process these indigenous fruits efficiently and have fast transit rates and high intake rates irrespective of species. Fruits were fed to the Turacos in separate trials to determine daily food and energy intake, assimilation efficiencies and digestive transit times. Digestive transit times of Knysna Turacos (c. 12–28 min) fall within the range of published examples for other frugivorous birds. Apparent assimilation efficiencies of the fruit ranged from c. 15–84% and were generally lower than those observed for other avian frugivores. Intake rates (in terms of wet weight) varied among the fruit species, and Knysna Turacos had greater intake rates on fruit which they are able to assimilate efficiently. Future studies looking at the nutritional composition of indigenous forest fruit may provide insight into the Knysna Turacos assimilation efficiency and consequently their food preferences and role as potential seed dispersers of fruiting tree species.
Zusammenfassung
Nahrungsaufnahmeraten, Verdauungseffizienz und Transitzeiten von Helmturakos ( Tauraco corythaix ), die mit einheimischen südafrikanischen Früchten gefüttert wurden
Pflanzen mit fleischigen Früchten und Fruchtfresser stehen in mutualistischer Beziehung—die Pflanzen bieten den Fruchtfressern eine Belohnung in Form von Fruchtfleisch, und diese verbreiten ihre Samen. Allerdings sind nicht alle Früchte gleichwertig im Hinblick auf die Energie, die für die Fruchtfresser nutzbar ist. Wir haben daher die Assimilationseffizienz von Früchten von sechs einheimischen Baumarten für einen fruchtfressenden Vogel, den Helmturako (Tauraco corythaix), gemessen. Wir haben vorhergesagt, dass die Turakos diese einheimischen Früchte effizient verarbeiten und schnelle Transitzeiten und hohe Aufnahmeraten haben, unabhängig von der Fruchtart. Die Früchte wurden den Turakos in separaten Versuchen gefüttert, um die tägliche Nahrungs- und Energieaufnahme, die Assimilationseffizienz und die Passagezeiten durch den Verdauungstrakt zu ermitteln. Die Transitzeiten der Helmturakos (ca. 12–28 min) fallen in den Bereich publizierter Beispiele für andere fruchtfressende Vögel. Die offensichtlichen Assimilationseffizienzen für die Früchte reichten von ca. 15–84% und waren allgemein niedriger als die für andere fruchtfressende Vögel beobachteten Werte. Aufnahmeraten (im Hinblick auf Feuchtmasse) variierten zwischen den Fruchtarten und waren höher für diejenigen Früchte, welche die Helmturakos effizienter verdauen können. Zukünftige Studien, welche die Nährstoffzusammensetzung einheimischer Waldfrüchte untersuchen, könnten Einblicke in die Assimilationseffizienz der Helmturakos und folglich in ihre Nahrungspräferenzen und ihre Rolle als potenzielle Samenverbreiter fruchtender Baumarten gewähren.
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Acknowledgments
A.-L. Wilson would like to thank the National Research Foundation for financial assistance. We thank the Pietermaritzburg SANBI Botanical Gardens and Isobel Johnson in particular for allowing and assisting us with fruit collection; Allison Young and the UKZN Botanical Gardens for allowing the use of their premises and for general assistance; Adam Shuttleworth for his valuable advice, proofreading and assistance with data collection; Mark Brown, the Animal House and Thami Mjwara for housing and caring for the Turacos; Rosemary Wilson, Lorinda Jordaan, James Harvey and Janet Taylor for assistance with data collection; Helen and Andy Shuttleworth for general assistance and land use; and Christina Potgieter, and Meyrick Bowker for general advice and assistance. Ethical clearance for this study has been approved by the Animal Ethics sub-committee of the University of KwaZulu-Natal.
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Communicated by C. G. Guglielmo.
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Wilson, AL., Downs, C.T. Food intake rates, assimilation efficiency, and transit times of Knysna (Tauraco corythaix) Turacos fed South African indigenous fruit. J Ornithol 153, 285–290 (2012). https://doi.org/10.1007/s10336-011-0741-y
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DOI: https://doi.org/10.1007/s10336-011-0741-y