Recent social loss, not chronic isolation, reshapes sleep in Drosophila

Drosophila melanogaster is widely used to study social experience, yet it remains unclear whether sleep phenotypes attributed to isolation reflect chronic deprivation or the consequences of a recent change in social state. Many fly studies alter social context again at the time of testing, making these possibilities difficult to distinguish. Here, we developed sociSleep, an identity-preserving tracking system that quantifies sleep without inducing social-state transitions. Using this approach, we found that chronic social isolation had little effect on sleep, whereas recent social loss robustly increased sleep. These findings show that recent social experience, rather than chronic isolation alone, is a major modulator of sleep in flies.