‘Hangry’ male fruit flies attack each other if they go without food


A fruit fly on a peach

blickwinkel/Alamy

If you’ve ever been hangry – so hungry you become angry – you have something in common with fruit flies. When these insects don’t get enough to eat, they lash out at others some even make a kind of fencing manoeuvre with their legs to fight other fruit flies.

“Male fruit flies display aggression that they direct towards other fruit flies. They don’t show these behaviours towards females,” says Jennifer Perry at the University of East Anglia in the UK.

Perry her colleagues used virgin male fruit flies (Drosophila melanogaster) to avoid any risk of mating-related aggression, separating them into groups of between 58 74 insects. One group was made up of flies that were allowed to feed throughout the experiment, while the remaining groups were fed then deprived for periods of 24, 48 or 72 hours.

At six to seven days old, pairs of flies from each group were placed together with a food source monitored over 5 hours.

Flies deprived of food had become increasingly aggressive, which peaked at 24 hours without anything to eat. The aggressive flies would lunge at chase each other or fence with their legs.

“I think we can all relate to feeling hangry after periods of food deprivation, what our study shows is that these feelings extend across even very distantly related animals,” says Perry. “They share lots of genes for their physiology behaviour with vertebrates, including humans. They’re a good model [for aggression] in that way.”

Even animals as seemingly simple as fruit flies have complex social lives respond to changes in their environment that affect the costs benefits of social behaviour like aggression, she says.

Journal reference: Animal Behaviour, DOI: 10.5287/bodleian:xrO2DD55e

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