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The giant honey bee Apis dorsata is unusual in being able to forage during both the day and the night. To date, the extent of this unique nocturnal foraging behavior and the environmental factors correlating with it have not been deeply investigated. We conducted the first systematic investigation into the nocturnal behavior of A. dorsata in Southern India by tracking the daily and nightly foraging activity of A. dorsata colonies in an urban environment for 8 months, over multiple seasons and lunar cycles. We found strong evidence that A. dorsata can behave in a manner that is "cathemeral" (active over the entire diel cycle) when environmental illumination is sufficient for nocturnal flight. However, workers were not always active even when the environment should have been bright enough for them to forage, suggesting that their nocturnal foraging behavior was also affected by seasonal changes in resource availability. The foraging activity observed during the day versus twilight versus night differed between seasons; notably, nocturnal activity rates were higher than diurnal activity rates during the winter. We found that at our study site A. dorsata routinely exhibits both diurnal and crepuscular activity, foraging just as intensely during the short twilight hours as during the day. The high foraging activity observed during the twilight and nighttime hours shows that A. dorsata colonies can extend their foraging beyond the daylight hours and reveals that foraging during these dimly lit hours is an integral part of their foraging ecology. This evidence of the importance of nocturnal and crepuscular foraging by A. dorsata paves the way for future studies examining the role of this species in nocturnal pollination networks, the contribution of nocturnal foraging to colony-level nutrition and energy budget, and the evolution of this unusual behavior. Future work comparing nocturnal activity in light polluted urban environments versus unpolluted natural environments is particularly encouraged to determine the generalizability of these findings., Competing Interests: The authors have declared that no competing interests exist.

Foraging animals must repeatedly decide whether to exploit current resources or explore to gain information and locate new resources. Balancing these two often mutually exclusive options is made more difficult by environmental changes that can occur predictably, as seen in daily patterns of nectar secretion in flowers, or unpredictably, as seen when resources are depleted by competitors. Recent experiences with predictable and unpredictable rewards potentially provide information that foraging animals can use to decide when it is beneficial to explore versus exploit. However, it is unclear how the predictability of recent experiences can shape an animal's future exploration after rewards vanish and they have no option but to search. We tested how experience with unpredictability related to two types of environmental change, unpredictability in reward location and unpredictability in daily timing of rewards, shaped the exploratory behaviour of honey bees in the absence of a reward. We found that honey bees that experienced unpredictable rewards in space or time were less precise in their exploration after those rewards vanished. In spatial experiments, bees searched more broadly within a patch if they had experience with unpredictably located rewards and spent more time searching outside the patch than bees that experienced predictably located rewards. In temporal experiments, bees that experienced unpredictably timed rewards distributed their search effort more broadly outside of the time they last received a high-quality reward; also, bees that experienced any change in reward searched more intensively regardless of how predictable the reward had been. In contrast to the differences in search precision, a bee's previous experience with spatial or temporal unpredictability of rewards did not change how persistently she searched for a reward. This study provides novel insights into how predictability of previous experiences can shape exploratory behaviour even in the absence of rewards. • Recent experience can inform honey bees' exploratory behaviour when rewards vanish. • Spatial or temporal reward unpredictability made honey bees search less precisely. • Bees searched more broadly within and outside a patch after unpredictable rewards. • Honey bees searched more intensively after experiencing temporally changing rewards. • Experience with unpredictability did not influence honey bee search persistence. [ABSTRACT FROM AUTHOR]

Honey bees (genus Apis) are important pollinators in Asian tropical agricultural and natural ecosystems, yet the Asian species remain vastly understudied compared to the European honey bee, Apis mellifera. We studied the temporal and spatial foraging patterns of three co-occurring Asian honey bee species in Bangalore, India, to gain a better understanding of how they coexist. We found evidence for temporal resource partitioning, with Apis cerana having activity peaks in the early mornings, Apis florea initiating foraging later in the day, and Apis dorsata having the potential to do much of its foraging activity at night, even when the moon is not yet up. Apart from the established species differences in foraging ranges, we found limited evidence of spatial partitioning of the landscape. Although individual colonies foraging in parallel often focused their foraging effort on different patches, all three species preferred foraging in cultivated garden areas to seminatural or urban areas. These observations add to the growing evidence for a key role of gardens as foraging habitat for bees in cities. [ABSTRACT FROM AUTHOR]