Sánchez Francisco, Korine Carmi, Kotler Burt P, Pinshow Berry
Mitrani Department of Desert Ecology, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel.
Naturwissenschaften. 2008 Jun;95(6):561-7. doi: 10.1007/s00114-008-0359-y. Epub 2008 Mar 5.
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.
乙醇在肉质果实中产生，这是微生物和植物自身对糖分进行发酵的结果；其浓度[EtOH]随果实成熟而增加。在低浓度时，乙醇是一种养分，而在高浓度时则具有毒性。我们假设乙醇对食果脊椎动物觅食行为的影响取决于其在食物中的浓度以及觅食者的身体状况。我们预测，当乙醇浓度与成熟果实中的浓度相似时，它会刺激食物消耗，而低于或高于成熟果实浓度的[EtOH]分别不会产生影响或会阻止觅食者。此外，我们预期在特定喂食日摄入的食物量会影响乙醇对觅食者的毒性作用，从而影响其在次日的觅食决策。因此，我们预测对于食物受限的觅食者来说，富含乙醇的食物比不含乙醇的食物价值更低。我们以埃及果蝠（埃及果蝠）为模型来检验我们的假设，发现乙醇并没有增加蝙蝠对食物的价值。高[EtOH]降低了饱腹蝙蝠对食物的价值。然而，对于食物受限的蝙蝠来说，富含乙醇的食物和不含乙醇的食物价值没有差异。因此，微生物通过产生乙醇可能会影响种子传播食果动物的觅食模式。然而，这些模式可能会因动物的身体状况而改变，因为它们可能会在中毒成本与获取的养分价值之间进行权衡。
