Fruit flies show ‘hangry’ behaviour when deprived of food, study shows

Just like humans, the tiny species becomes aggressive on an empty stomach

Fruit flies react like people to hunger (Getty Images/iStockphoto)

If you’ve ever noticed your partner becoming irritable and aggressive when their stomach is empty, take comfort from knowing they are not alone – fruit flies also become “hangry”.

Scientists at the University of East Anglia (UEA) and Oxford University discovered that male fruit flies, which feed on decaying fruit, grew ever more combative the longer they went without food, for up to 24 hours.

After a day, their aggression reached a plateau.

Researchers scanned vials of male fruit flies and different amounts of food, recording the number of lunges and tussles they got into and how much they occupied the food patch.

Senior author Jen Perry, of UEA’s School of Biological Sciences, said: “On the one hand, going hungry might lead to a weakened state, such that hungry individuals are less likely to win fights and so display aggression less often.

“On the other, hungry individuals might be more motivated to fight to compete for food, leading to displays of aggression or ‘hanger’.

“We found that hungry male fruit flies display more hostility toward each other.

“They’re more likely to aggressively lunge at each other and to swat at each other with their legs, and they spend more time defending food patches.

“The hungrier they get, the more combativeness they display.

“In other words, just like humans, fruit flies get ‘hangry’.”

Doctors say that in humans low blood sugar triggers hormones to be released into the bloodstream, including fight-or-flight hormone adrenalin and cortisol, a stress hormone that can cause aggression.

Low blood sugar may also affect the brain functions that control impulses and drive instinctive behaviour.

Some people struggle to concentrate on an empty stomach, for instance.

Danielle Edmunds, who conducted the experiments at Oxford, said: “Increased aggression by food-deprived males might be a strategy to maximise short-term reproductive output in environments where survival is uncertain, but this will require further investigation.

“Our other studies show that show that poor food conditions early in life have just the opposite effect on aggression.

“Flies that grow up experiencing limited food are less aggressive as adults.”

No flies died during the experiment.