London, Apr 16 : If you consider drunken behaviour and junk food only humans' domain, here's something interesting for you, under-the-influence bats are more likely than their sober counterparts to eat junk food, says a new study.
With the knowledge that fruit-eating bats frequently encounter fermenting fruits, Francisco Sanchez and his colleagues at the Jacob Blaustein Institutes for Desert Research at Ben-Gurion University of the Negev, Israel, decided to investigate what effects, if any, consumption of ethanol from fermentation had on feeding behaviour.
In order to explore this, the research team studied Egyptian fruit bats, Rousettus aegyptiacus.
In the study, 12 bats were placed in a cage and given feeding containers filled with a mixture of soy protein infant formula, sucrose, water and one of six concentrations of ethanol that ranged from 0 percent to 2 percent.
Each day the bats were given a different concentration of ethanol in their food. Uneaten food was removed and measured.
The analysis of the study showed that bats actively avoided concentrations of ethanol above 1 percent yet below that threshold level their behaviour was unchanged.
Wondering how hunger might affect this, the researchers ran a similar experiment with hungry bats.
The team had expected ethanol in low concentrations to increase the appetite of well-fed bats, because low levels of ethanol are thought to be used by fruit-bearing plants to encourage seed dispersers to eat more before they leave.
They expected high levels of ethanol to decrease appetite because the chemical's toxic effect. In hungry bats, the team expected intoxication from the ethanol to be more pronounced and hypothesized that this would reduce appetite.
But the research team reported that neither hypothesis proved to be correct. Well-fed bats did not eat more when consuming low levels of ethanol, and avoided eating high concentrations of ethanol altogether.
In contrast, hungry bats, ate the same amount of food containing ethanol as they did normal food, regardless of ethanol content.
"This is probably because starving to death poses a higher threat than intoxication," Nature quoted Sanchez, as saying.
However, he is quick to add that hungry bats may be more willing to become intoxicated in captivity, where they know they are safe.
"Wild tests are needed," he added.
"We did not know that non-human mammals could respond to such low ethanol levels," said physiologist Robert Dudley at the University of California, Berkeley.
Some fruits develop concentrations as high as 8.1percent.
"With those fruits you can smell it, but that 1% concentrations are having an effect on bat behaviour is remarkable," he said.
The study is published in the journal Naturwissenschaften.