For centuries, anecdotal reports of elephants getting inebriated on the fermented fruit of marula trees have persisted. In the late 1830s, a French naturalist wrote of elephants' affinity for a 'gentle warming of the brain' courtesy of fruity hooch, and – some 180 years later – stories of overindulgent elephants are maintained thanks to images and videos shared widely online (these photos of a messy pile of pachyderms, for example). But biologists from Bristol University ruined all the fun when they put the claims of drunken elephants to rest in a study published in 2006.

Drunk Elephants Marula 2 2014 05 13
Come on, buddy, let's get you home." Image © Singita

Now, new research examining how different mammal species handle their liquor has reopened the case and provided some fresh insight into how the mega mammals process their booze.

Previous research, like that carried out in by the Bristol biologists, looked at the amount of ethanol in fermented fruit, examined how quickly humans break down alcohol, and then adjusted this calculation to elephantine proportions to work out how much fermented fruit it would take to get a five-ton mammal on its (very large) ear. "However, there is one fatal flaw in this logic," Mareike Janiak, a postdoctoral scholar in primate genomics and one of the authors of the new study, explained in an article for The Conversation. "It assumes that elephants are able to break down ethanol as quickly as humans do. Research suggests that this assumption might not be true."

Many species rely on fruits and nectars as a rich source of energy, but natural fermentation can lead to significant alcohol concentrations – as high as 8.1% in some fruits, according to the authors of the paper published in the journal Biology Letters. So to benefit from this alcohol-laced energy source, nectar and fruit-eating mammals have evolved the ability to efficiently break down ethanol to avoid getting schnockered (something that could be deadly for fruit bats that have to fly home after a night spent sipping on moonshine).

Drunk or playful?

To better understand how different mammals metabolise alcohol, the researchers focused on a gene called ADH7 which is present in a number of animal species. Its job is to set in motion the creation of enzymes that help to break down alcohol. Most primates have an ADH7 mutation that allows for more efficient ethanol metabolisation – something that humans are particularly good at it as a result of a long history eating fruits and nectars. However, the same can not necessarily be said for other species.

Horses, cows and elephants do not have an ADH7 mutation suggesting that they probably can't handle their plonk. "It’s possible that elephants have another way of breaking down ethanol. But it’s very unlikely that the efficiency with which they can do this is comparable to that of humans," Janiak explains, adding that the process for metabolising ethanol is very complex.

So can elephants get drunk? Maybe. The researchers point out that it is "almost certainly erroneous to make inferences about one species based on another with divergent physiologies and ecologies." For all their heft, elephants may, in fact, be lightweights when it comes to alcohol.

Top header image: Ton Rulkens, Flickr