Hornets can hold their alcohol like no other animal on Earth

A species of hornet that often munches on foods containing alcohol can hold its liquor, without any side effects, at levels that no other known animal can tolerate.

“This is crazy,” says study author Sofia Bouchebti at the Ben-Gurion University of the Negev in Israel.

The diet of the oriental hornet (Vespa orientalis) consists of nectar and ripe fruits, including grapes. This fruit contains sugar that, when it naturally ferments over time, turns into ethanol.

While ethanol can be nutritious for animals, it is also highly intoxicating. Even animals that routinely eat fermenting fruits – like fruit flies and tree shrews – cannot stomach more than 4 per cent ethanol in their meals, according to Bouchebti and her colleagues.

But when Bouchebti’s team gave hornets nothing to eat for a week except a range of sugary solutions containing different quantities of ethanol – between 1 and 80 per cent – the hornets seemed to be completely unaffected. Both their behaviour and lifespan remained unchanged. What makes this particularly surprising is that the solutions with 80 per cent ethanol contain an alcohol content four times as high as anything found in nature.

“In the beginning, we did the experiment only with 20 per cent [ethanol] and we were already amazed,” says study author Eran Levin at Tel Aviv University in Israel. The 80 per cent ethanol figure is “even harder to believe”.

Analysis of the genomes of several hornet species suggests the insects have two to four copies of a gene that produces NADP+, which helps break down alcohol. The researchers think this might help explain why the oriental hornet – and possibly other hornet species – can handle such large quantities of alcohol.

These findings “remind us that we are not alone in our fondness for alcohol”, says James Fry at the University of Rochester in New York. But he isn’t persuaded that hornets are the only organisms that can handle this much alcohol, because data from other animal studies is hard to compare.

The hornets’ penchant for alcohol might give them a competitive edge when it comes to feeding on highly fermented foods, which are highly nutritious, says Irene Stefanini at the University of Turin in Italy. She thinks the hornets’ tolerance is probably related to the animals’ mutualistic relationship with the fermenting brewer’s yeast Saccharomyces cerevisiae, which her studies have shown reside, survive and even mate within hornets’ intestines. Maybe the hornets help the yeasts move around from fruit to fruit, while the yeasts help the hornets find energy-rich foods.