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SUMMARYSleep is a dynamic phenomenon that changes throughout an organismʼs lifetime, relating to possible age-or task-associated changes in health, learning ability, vigilance and fitness. Sleep has been identified experimentally in many animals, including honey bees (Apis mellifera). As worker bees age they change castes, typically performing a sequence of different task sets (as ʻcell cleanersʼ, ʻnurse beesʼ, ʻfood storersʼ and ʻforagersʼ). Belonging to a caste could differentially impact the duration, constitution and periodicity of a beeʼs sleep. We observed individually marked bees within observation hives to determine castedependent patterns of sleep behavior. We conducted three studies to investigate the duration and periodicity of sleep when bees were outside comb cells, as well as duration of potential sleep when bees were immobile inside cells. All four worker castes we examined exhibited a sleep state. As bees aged and changed tasks, however, they spent more time and Supplementary material available online at

SUMMARY Multimodal signals (acoustic+visual) are known to be used by many anuran amphibians during courtship displays. The relative degree to which each signal component influences female mate choice, however, remains poorly understood. In this study we used a robotic frog with an inflating vocal sac and acoustic playbacks to document responses of female túngara frogs to unimodal signal components (acoustic and visual). We then tested female responses to a synchronous multimodal signal. Finally, we tested the influence of spatial and temporal variation between signal components for female attraction. Females failed to approach the isolated visual cue of the robotic frog and they showed a significant preference for the call over the spatially separate robotic frog. When presented with a call that was temporally synchronous with the vocal sac inflation of the robotic frog, females did not show a significant preference for this over the call alone; when presented with a call that was temporally asynchronous with vocal sac inflation of the robotic frog, females discriminated strongly against the asynchronous multimodal signal in favor of the call alone. Our data suggest that although the visual cue is neither necessary nor sufficient for attraction, it can strongly modulate mate choice if females perceive a temporal disjunction relative to the primary acoustic signal.

Sleep is essential for basic survival, and insufficient sleep leads to a variety of dysfunctions. In humans, one of the most profound consequences of sleep deprivation is imprecise or irrational communication, demonstrated by degradation in signaling as well as in receiving information. Communication in nonhuman animals may suffer analogous degradation of precision, perhaps with especially damaging consequences for social animals. However, society-specific consequences of sleep loss have rarely been explored, and no function of sleep has been ascribed to a truly social (eusocial) organism in the context of its society. Here we show that sleep-deprived honey bees (Apis mellifera) exhibit reduced precision when signaling direction information to food sources in their waggle dances. The deterioration of the honey bee's ability to communicate is expected to reduce the foraging efficiency of nestmates. This study demonstrates the impact of sleep deprivation on signaling in a eusocial animal. If the deterioration of signals made by sleep-deprived honey bees and humans is generalizable, then imprecise communication may be one detrimental effect of sleep loss shared by social organisms.dance language | signal precision | recovery sleep | sleep rebound D eprivation of sleep can result in dire consequences to health and to cognitive performance (1-3). When deprived of sleep, humans are susceptible to communication lapses, both when signaling (4, 5) and when receiving (6) information. Human speech performance, such as word fluency and intonation, declines (7). A speaker's voice is sensitive to fatigue (8), with both fundamental frequency and word duration differing in sleep-deprived subjects (9). Speech deterioration is so obvious after sleep deprivation that "rambling, incoherent speech for brief periods" features in a cognitive disorganization scale (10). Although the potential exists for sleep to impact communication in nonhuman animals, we are aware only of studies addressing the role of sleep in song learning in zebra finches (11,12).In the present study, we investigated a possible degradation of social function by testing the effect of sleep deprivation on the precision of signaling in European honey bees (Apis mellifera Linnaeus, 1758). Honey bees regularly inform nestmate workers about the distance and direction to desirable foraging and nestsite locations by performing waggle dances (Fig. 1A), in which the distance to the advertised destination is indicated by the duration of the waggle phase of the dance, and the destination's direction relative to the sun's azimuth is indicated by the angle of the dance relative to the vertical (i.e., dance angle) (Fig. 1A) (13). Imprecision in a bee's performance of the waggle dance could result in degraded transfer of information and a consequent decline in foraging efficiency for vital resources (14, 15).We hypothesized that depriving honey bees of sleep would decrease the precision of their dance's direction and distance information. For directional precision, we predicted t...

Social animals can obtain valuable information from group members, but sometimes experience conflicts between this social information and personal information obtained through their own experience. Experienced honey bee foragers (Apis mellifera) have personal information about familiar food sources, and can also obtain social information by following waggle dances. However, it is unclear whether temporarily unemployed foragers whose visits to a food source have been interrupted make full use of social information from dancers or rely primarily on their own personal information to determine whether their familiar food source is active again. We hypothesized that experienced foragers should pay more attention to the social information in waggle dances when foraging errors that can arise from ignoring social information are more costly. We manipulated the cost of mistakenly flying to a familiar but unprofitable food source by training bees to visit feeders that were either close (100 m) or far (1000 m) from the hive and found that temporarily unemployed foragers who had been trained to forage at more distant feeders were more likely to pay attention to social information about food source location. Our findings demonstrate that experienced forager bees can flexibly alter the extent to which they rely on social, as opposed to personal, information and are more likely to fully utilize social information from dancers when foraging errors are more costly.