Male ‘Hangry’ fruit flies attack each other if they go without food
If you’ve ever been hungry – so hungry you get angry – you have a little something in common with fruit flies. When these insects don’t have enough to eat, they aggressively prey on others and some even make some sort of fencing maneuver with their paws to fight with other fruit flies.
“Male fruit flies show an aggressiveness that they direct towards other fruit flies. They don’t show these behaviors towards women, ”says Jennifer Perry of the University of East Anglia in the UK.
Perry and his colleagues separated the flies from the virgin male fruits (Drosophila melanogaster) in five groups of 58 to 74 insects. One group consisted of newly emerged adults who had not fed from their larval stage, while another consisted of flies that were allowed to feed throughout the experiment. The other groups were fed and then deprived for periods of 24, 48 or 72 hours.
At six to seven days of age, pairs of flies from each group were placed with food and monitored for 5 hours. The team observed the pairs 16 or 32 times for 5 hours to record their behavior.
The food starved flies had become increasingly aggressive, peaking at 24 hours without food. The aggressive flies would rush in and chase each other or close each other with their paws.
“I think we can all feel hungry after periods of food deprivation, and what our study shows is that those feelings extend even to very distant animals,” says Perry. “They share many genes for their physiology and behavior with vertebrates, including humans. It is a good model [for aggression] in this way.”
Even animals as simple as a fruit fly have complex social lives and respond to changes in their environment that affect the costs and benefits of social behavior like aggression, she says.
Journal reference: Animal behavior, DOI: 10.5287 / bodleian: xrO2DD55e
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