Naturwissenschaften

, Volume 95, Issue 6, pp 561–567 | Cite as

Ethanol concentration in food and body condition affect foraging behavior in Egyptian fruit bats (Rousettus aegyptiacus)

  • Francisco Sánchez
  • Carmi Korine
  • Burt P. Kotler
  • Berry Pinshow
Original Paper

Abstract

Ethanol occurs in fleshy fruit as a result of sugar fermentation by both microorganisms and the plant itself; its concentration [EtOH] increases as fruit ripens. At low concentrations, ethanol is a nutrient, whereas at high concentrations, it is toxic. We hypothesized that the effects of ethanol on the foraging behavior of frugivorous vertebrates depend on its concentration in food and the body condition of the forager. We predicted that ethanol stimulates food consumption when its concentration is similar to that found in ripe fruit, whereas [EtOH] below or above that of ripe fruit has either no effect, or else deters foragers, respectively. Moreover, we expected that the amount of food ingested on a particular day of feeding influences the toxic effects of ethanol on a forager, and consequently shapes its feeding decisions on the following day. We therefore predicted that for a food-restricted forager, ethanol-rich food is of lower value than ethanol-free food. We used Egyptian fruit bats (Rousettus aegyptiacus) as a model to test our hypotheses, and found that ethanol did not increase the value of food for the bats. High [EtOH] reduced the value of food for well-fed bats. However, for food-restricted bats, there was no difference between the value of ethanol-rich and ethanol-free food. Thus, microorganisms, via their production of ethanol, may affect the patterns of feeding of seed-dispersing frugivores. However, these patterns could be modified by the body condition of the animals because they might trade-off the costs of intoxication against the value of nutrients acquired.

Keywords

Chiroptera Food selection Giving-up density State-dependent foraging Toxins 

Notes

Acknowledgements

We thank R. Gluhih for her indispensable help with bat maintenance, and for commenting on the manuscript. Three anonymous reviewers and the editor of the journal, Tatiana Czeschlik, provided comments that helped us improve the document. We thank Sulbar Hazor Ltd. Israel, for generously donating soy protein. This study was supported, in part, by a student research grant to F.S. from the Mitrani Department of Desert Ecology (MDDE). This research was done under permit 18150 from Israel Nature and National Parks Protection Authority. This is paper number 591 of the MDDE.

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Francisco Sánchez
    • 1
  • Carmi Korine
    • 1
  • Burt P. Kotler
    • 1
  • Berry Pinshow
    • 1
  1. 1.Mitrani Department of Desert Ecology, The Jacob Blaustein Institutes for Desert ResearchBen-Gurion University of the NegevMidreshet Ben-GurionIsrael

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