Work or sleep? Honeybee foragers opportunistically nap during the day when forage is not available

foraging honeybee nap plasticity shift work sleep Shifts in work schedules test humans ' capacity to be fl exibl e in the timing of both work and sleep. Honeybee. Apis rnellifera. foragers also shift their work schedules. but how flexible they are in the timing of sl eep as they shift the timing of work is unknown. despite the importance of colonY-level plasticity in the face of a changing environment. We hypothesized that sleep schedules of foragers are not fixed and instead vary depending on the time when food is available. We trained bees to visit a food source made available for several hours in the early morning (AM) or several hours in the late afternoon (PM). then monitored their sleep behaviour for 24 h after training. specifically comparing their sleep during the AM and PM periods previously designated as training periods. Following AM training. honeybee foragers slept more during the afternoon than during the morning. but following PM training. the same bees 'slept in' the next morning. and so slept more in the morning than in the afternoon. Although foragers did not change the total amount of time devoted to each of their behaviours (including sleep). the timing of their sleep did change. Thus. plasticity in timing of foraging was matched by plasticity in timing of sleep. The apparent correlation between the timing patterns of foraging and sleeping demonstrates temporal plasticity of sleep under ecologically realistic conditions in an invertebrate. Testing how shift work affects the health and performance of honeybees may shed light on the role of sleep in a nonhuman socia l animal. Humans often institute 'shift work'. an employment practise that attempts to make full use of each day's time by requiring employees to accommodate shifting work schedules. Extreme changes in circadian cycles of work/sleep can cause varied health and performance problems (reviewed by Rajaratnam & Arendt 2001; Garbarino et al. 2002; Arendt 2010) ranging from cancers and gastrointestinal dysfunction (Costa 1996) to degraded ability to detect simulated threats (weapons) as a luggage screener (Basner et al. 2008). Extreme shifting of work schedules requires shifting of sleep schedules. whereupon planned napping can aid in perfol'mance (Smith-Coggins et al. 2006). even under stable daytime work schedules (reviewed by Dhand & Sohal 2006). The ability to respond flexibly to changes in work schedules by changing sleep schedules exists in humans. but is not well established in nonhuman animals …