TY - JOUR
T1 - The influence of ethanol on feeding in the frugivorous yellow-vented bulbul (Pycnonotus xanthopygos)
AU - Mazeh, Shunit
AU - Korine, Carmi
AU - Pinshow, Berry
AU - Dudley, Robert
N1 - Funding Information:
We thank Francisco Sanchez for help with statistical methods, Dr. Michał Wojciechowski for valuable technical help and both for commenting on early drafts of this paper. We also thank Amram Zabari who provided indispensable assistance, both in the laboratory and in the field, throughout this study. Soy protein added to the birds’ food was generously donated by Sulbar-Hazor Inc. This research was funded by the US-Israel Binational Science Foundation 2001038 to CK, BP and RD and a student support grant from the Mitrani Department of Desert Ecology to SM. This is paper number 583 of the MDDE.
PY - 2008/3/1
Y1 - 2008/3/1
N2 - The sugars in fleshy fruits provide a rich source of energy to frugivorous animals. However, these carbohydrates also serve as a substrate for alcoholic fermentation by yeasts, ethanol being the main by-product of this process. Ethanol ingestion via frugivory thus occurs in a diverse assemblage of invertebrate and vertebrate taxa, including numerous species of birds. We tested the roles of ethanol as an odor cue for resource location by adult yellow-vented bulbuls (Pycnonotus xanthopygos) and as a possible appetite stimulant in feeding trials with artificial food. We hypothesized (1) that the odor of ethanol does not serve as a food-locating cue in diurnal frugivorous passerine birds, and predicted that the choice of food source and the mass of food eaten by such birds will not be influenced by the odor of ethanol. We further hypothesized (2) that food intake in passerine birds is affected by ingestion of ethanol according to its concentration [EtOH], and predicted that food intake will follow a bell-shaped curve in relation to [EtOH]. In accord with hypothesis (1) and its prediction, we found that the odor of ethanol did not affect food preferences, in either ethanol-naïve or ethanol-experienced yellow-vented bulbuls, when presented at concentrations found in naturally ripe fruit (0.0-1.0%); this suggests that the odor of ethanol is not a food-locating cue for the bulbuls. Hypothesis (2) was partially supported, namely at low [EtOH] (0-3%), food intake was constant and at high [EtOH] (3%) food intake decreased, following only the right half of the predicted bell-shaped response. Ethanol-naïve birds showed no preference towards any [EtOH] presented in two-way choice trials. However, daily food intake in ethanol-experienced bulbuls in single option trials decreased by an average of 36% when the artificial food contained the highest tested concentration of ethanol (3.0%). We suggest that decreasing food intake when food ethanol concentration is relatively high may be a means of avoiding intoxication and is related to the ethanol-metabolizing ability of the bird.
AB - The sugars in fleshy fruits provide a rich source of energy to frugivorous animals. However, these carbohydrates also serve as a substrate for alcoholic fermentation by yeasts, ethanol being the main by-product of this process. Ethanol ingestion via frugivory thus occurs in a diverse assemblage of invertebrate and vertebrate taxa, including numerous species of birds. We tested the roles of ethanol as an odor cue for resource location by adult yellow-vented bulbuls (Pycnonotus xanthopygos) and as a possible appetite stimulant in feeding trials with artificial food. We hypothesized (1) that the odor of ethanol does not serve as a food-locating cue in diurnal frugivorous passerine birds, and predicted that the choice of food source and the mass of food eaten by such birds will not be influenced by the odor of ethanol. We further hypothesized (2) that food intake in passerine birds is affected by ingestion of ethanol according to its concentration [EtOH], and predicted that food intake will follow a bell-shaped curve in relation to [EtOH]. In accord with hypothesis (1) and its prediction, we found that the odor of ethanol did not affect food preferences, in either ethanol-naïve or ethanol-experienced yellow-vented bulbuls, when presented at concentrations found in naturally ripe fruit (0.0-1.0%); this suggests that the odor of ethanol is not a food-locating cue for the bulbuls. Hypothesis (2) was partially supported, namely at low [EtOH] (0-3%), food intake was constant and at high [EtOH] (3%) food intake decreased, following only the right half of the predicted bell-shaped response. Ethanol-naïve birds showed no preference towards any [EtOH] presented in two-way choice trials. However, daily food intake in ethanol-experienced bulbuls in single option trials decreased by an average of 36% when the artificial food contained the highest tested concentration of ethanol (3.0%). We suggest that decreasing food intake when food ethanol concentration is relatively high may be a means of avoiding intoxication and is related to the ethanol-metabolizing ability of the bird.
KW - Ethanol
KW - Fermentation
KW - Food consumption
KW - Fruit-eating birds
KW - Olfaction
KW - Side-bias
KW - Yellow-vented bulbul
UR - http://www.scopus.com/inward/record.url?scp=39449137516&partnerID=8YFLogxK
U2 - 10.1016/j.beproc.2007.10.003
DO - 10.1016/j.beproc.2007.10.003
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AN - SCOPUS:39449137516
VL - 77
SP - 369
EP - 375
JO - Behavioural Processes
JF - Behavioural Processes
SN - 0376-6357
IS - 3
ER -