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First published online April 18, 2008
Journal of Experimental Biology 211, 1475-1481 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013268
Sugars are complementary resources to ethanol in foods consumed by Egyptian fruit bats
Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990 Midreshet Ben-Gurion, Israel
* Author for correspondence at present address: Facultad de Ciencias Ambientales, Universidad de Ciencias Aplicadas y Ambientales, Calle 222 # 55–37, Bogotá, Colombia, South America (e-mail: fasbos{at}gmail.com)
Accepted 10 March 2008
Food resources are complementary for a forager if their contribution to
fitness is higher when consumed together than when consumed independently,
e.g. ingesting one may reduce the toxic effects of another. The concentration
of potentially toxic ethanol, [EtOH], in fleshy fruit increases during
ripening and affects food choices by Egyptian fruit bats, becoming deterrent
at high concentrations (
1%). However, ethanol toxicity is apparently
reduced when ingested along with some sugars; more with fructose than with
sucrose or glucose. We predicted (1) that ingested ethanol is eliminated
faster by bats eating fructose than by bats eating sucrose or glucose, (2)
that the marginal value of fructose-containing food (food+fructose) increases
with increasing [EtOH] more than the marginal value of sucrose- or
glucose-containing food (food+sucrose, food+glucose), and (3) that by
increasing [EtOH] the marginal value of food+sucose is incremented more than
that of food+glucose. Ethanol in bat breath declined faster after they ate
fructose than after eating sucrose or glucose. When food [EtOH] increased, the
marginal value of food+fructose increased relative to food+glucose. However,
the marginal value of food+sucrose increased with increasing [EtOH] more than
food+fructose or food+glucose. Although fructose enhanced the rate at which
ethanol declined in Egyptian fruit bat breath more than the other sugars, the
bats treated both fructose and sucrose as complementary to ethanol. This
suggests that in the wild, the amount of ethanol-containing fruit consumed or
rejected by Egyptian fruit bats may be related to the fruit's own sugar
content and composition, and/or the near-by availability of other sucrose- and
fructose-containing fruits.
Key words: fructose, frugivory, glucose, marginal value of food, sucrose, toxins
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  K. Phillips ALCOHOL IS A NECESSARY EVIL FOR BATS J. Exp. Biol., May 1, 2008; 211(9): iii - iii. [Full Text] [PDF]
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