Digestive efficiency of Knysna and purple-crested turacos fed varying concentrations of equicaloric and equimolar artificial fruit

Journal of Experimental Biology

2011

Self Cite

SUMMARYThe effects that different fruit sugar types and concentrations have on food preferences of avian frugivores have been relatively poorly studied. Although it has been recently advocated that preference is based on equicaloric energy it is also important to note whether preferences change as energy content changes. Therefore, sugar preferences of equicaloric and equimolar artificial fruit of different sugar types at varying concentrations and molarities were investigated in two relatively large South African frugivores, Knysna (Tauraco corythaix) and purple-crested (Gallirex porphyreolophus) turacos. Artificial fruits containing 6.6, 12.4 or 22% sucrose or glucose, and artificial fruits containing 0.42, 0.83 or 1.66moll -1 sucrose or glucose, were used to determine sugar preferences. Knysna turacos preferred the sucrose to the glucose equicaloric artificial fruit diet at low concentrations whereas purple-crested turacos showed no preference for either diet. Both turacos species preferred the sucrose equimolar artificial fruit diet to the glucose at low concentrations. At high concentrations neither species showed a preference for either equicaloric or equimolar artificial fruit diets. This suggests that energy requirements influence food preferences more than sugar type and that birds will select fruit that is higher in energy irrespective of sugar type. This complements an earlier study on digestion of differing equicaloric and equimolar artificial fruit sugar types. It again emphasizes the need for future studies looking at the composition of indigenous forest fruit sugars in order to obtain insight into the role of these avian frugivores as potential seed dispersers of fruiting tree species.

Section: Discussionsupporting

confidence: 91%

Food preferences of Knysna and purple-crested turacos fed varying concentrations of equicaloric and equimolar artificial fruit

Wilson

Journal of Experimental Biology

2011

Self Cite

“…Indeed the assimilation efficiencies may have been higher once their guts had had time to adjust to the fruit. In a previous study (Wilson and Downs 2011a), apparent assimilation efficiencies of both Turaco species ranged from 61.4 to 90.0% and 60.2 to 92.4% for equicaloric and equimolar artificial fruit diets (without pulp), respectively.…”

Section: Discussionmentioning

confidence: 76%

Food intake rates, assimilation efficiency, and transit times of Knysna (Tauraco corythaix) Turacos fed South African indigenous fruit

Wilson

2011

J Ornithol

Self Cite

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. ZusammenfassungNahrungsaufnahmeraten, Verdauungseffizienz und Transitzeiten von Helmturakos (Tauraco corythaix), die mit einheimischen sü dafrikanischen Früchten gefü ttert 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 Nährstoff-zusammensetzung einheimischer Waldfrüchte untersuchen, könnten Einblicke in die Assimilationseff...

“…Energy assimilation has been quantified for artificial fruit diets (Witmer 1998, Wellmann & Downs 2009, Wilson & Downs 2011), nectar diets (Brown & Downs 2003, Brown et al. 2010) and indigenous fruit diets (Witmer & Van Soest 1998), but not for invasive alien fruits.…”

mentioning

confidence: 99%

Digestion of fruit of invasive alien plants by three southern African avian frugivores

Jordaan

Johnson

2011

Ibis

Self Cite

Many highly invasive plants are fleshy-fruited and owe their invasiveness largely to mutualisms formed with local dispersers. The energetic benefits gained by frugivores from ingestion of fruits of invasive alien plants remain poorly documented. We assess whether avian frugivores process fruits of invasive alien plants effectively to meet their daily energetic requirements. Four fleshy-fruited plant species that are invasive in southern Africa were considered -Solanum mauritianum, Cinnamomum camphora, Lantana camara and Psidium guajava. Their fruits were fed to three common generalist frugivores -Red-winged Starling Onychognathus morio, Speckled Mousebird Colius striatus and Dark-capped Bulbul Pycnonotus tricolor -to determine the efficiency of digestion. Energetic parameters calculated for all fruit diets varied significantly between frugivore species. Speckled Mousebirds and Dark-capped Bulbuls maintained body mass and efficiently processed all four fruit types, whereas Red-winged Starlings only did so on C. camphora and S. mauritianum diets. These results explain why these fruits are attractive to local avian frugivores. Furthermore, these avian frugivores processed large quantities of invasive fruits, thereby serving as potentially efficient dispersers.