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A common management intervention to support declining wild pollinators is 'pollinator planting'. However, despite years of inclusion in conservation initiatives, global pollinator declines continue.Using the agent‐based model BEE‐STEWARD with two example species, Bombus terrestris (L. 1758) and B. pascuorum (Scopoli, 1763) (Hymenoptera: Apidae), we explore when during the year bumblebee resource demand is the highest and how that relates to seasonal changes in colony composition (numbers of eggs, larvae, pupae and adults). We then examine the impact of two‐week periods of resource scarcity across the year. Finally, we explore how enhancement with early spring‐blooming herbaceous species or trees changes colony survival and queen production.In the United Kingdom, there is a previously under‐appreciated 'hungry gap' for bumblebees in March–April, before the peak flight period, driven by the demands of larvae for protein and thermoregulation in the colony, rather than the number of adult bees.A 2‐week gap in forage availability during this period drives a 50%–87% drop in the production of daughter queens. Adding early‐blooming species in the model had significant, positive, long‐term effects on colony survival probability and daughter queen production.Pollinator‐planting initiatives in both national and international conservation schemes need to include plants that flower up to 1 month before the adults of target social pollinator species are apparent in the field, during the period that larvae dominate the colony. This approach is likely to increase colony survival and queen production, contributing towards halting and reversing global pollinator decline. [ABSTRACT FROM AUTHOR]

The invasive hornet Vespa velutina nigrithorax is considered a proliferating threat to pollinators in Europe and Asia. While the impact of this species on managed honey bees is well-documented, effects upon other pollinator populations remain poorly understood. Nonetheless, dietary analyses indicate that the hornets consume a diversity of prey, fuelling concerns for at-risk taxa. Here, we quantify the impact of V. velutina upon standardised commercially-reared colonies of the European bumblebee, Bombus terrestris terrestris. Using a landscape-scale experimental design, we deploy colonies across a gradient of local V. velutina densities, utilising automated tracking to non-invasively observe bee and hornet behaviour, and quantify subsequent effects upon colony outcomes. Our results demonstrate that hornets frequently hunt at B. terrestris colonies, being preferentially attracted to those with high foraging traffic, and engaging in repeated—yet entirely unsuccessful—predation attempts at nest entrances. Notably however, we show that B. terrestris colony weights are negatively associated with local V. velutina densities, indicating potential indirect effects upon colony growth. Taken together, these findings provide the first empirical insight into impacts on bumblebees at the colony level, and inform future mitigation efforts for wild and managed pollinators. The influence of the invasive hornet Vespa velutina on Bombus terrestris colonies is quantified along a gradient of hornet densities, revealing negative impacts upon B. terrestris colony growth. [ABSTRACT FROM AUTHOR]

The demand for agent‐based models to explore the effects of environmental change on pollinator population dynamics is growing. However, models need a simple yet flexible interface to enable adoption by a wide range of stakeholders.We introduce BEE‐STEWARD: a research and decision‐support software tool, enabling researchers, policymakers, land management advisors and practitioners to predict and compare the effects of bee‐friendly management interventions on bumblebee populations over several years.BEE‐STEWARD integrates the BEESCOUT and Bumble‐BEEHAVE agent‐based models of bumblebee behaviour, colony growth and landscape exploration into a user‐friendly interface, with reconstructed code, and expanded functionality. Bespoke automatic reports can be created to illustrate how different land management interventions can affect the densities of bumblebees and their colonies over time.BEE‐STEWARD could be an important virtual test bed for scientists exploring the impacts of different stressors on bumblebees and used by those with little or no modelling experience, enabling a shared methodology between research, policy and practice. [ABSTRACT FROM AUTHOR]

Bumblebees (Bombus spp.) rely on an abundant and diverse selection of floral resources to meet their nutritional requirements. In farmed landscapes, mass‐flowering crops can provide an important forage resource for bumblebees, with increased visitation from bumblebees into mass‐flowering crops having an additional benefit to growers who require pollination services. This study explores the mutualistic relationship between Bombus terrestris L. (buff‐tailed bumblebee), a common species in European farmland, and the mass‐flowering crop courgette (Cucurbita pepo L.) to see how effective B. terrestris is at pollinating courgette and in return how courgette may affect B. terrestris colony dynamics. By combining empirical data on nectar and pollen availability with model simulations using the novel bumblebee model Bumble‐BEEHAVE, we were able to quantify and simulate for the first time, the importance of courgette as a mass‐flowering forage resource for bumblebees. Courgette provides vast quantities of nectar to ensure a high visitation rate, which combined with abundant pollen grains, enables B. terrestris to have a high pollination potential. While B. terrestris showed a strong fidelity to courgette flowers for nectar, courgette pollen was not found in any pollen loads from returning foragers. Nonetheless, model simulations showed that early season courgette (nectar) increased the number of hibernating queens, colonies, and adult workers in the modeled landscapes. Synthesis and applications. Courgette has the potential to improve bumblebee population dynamics; however, the lack of evidence of the bees collecting courgette pollen in this study suggests that bees can only benefit from this transient nectar source if alternative floral resources, particularly pollen, are also available to fulfill bees' nutritional requirements in space and time. Therefore, providing additional forage resources could simultaneously improve pollination services and bumblebee populations. By combining empirical data on nectar and pollen availability with model simulations using the novel bumblebee model Bumble‐BEEHAVE, we were able to quantify and simulate for the first time, the importance of courgette as a mass‐flowering forage resource for bumblebees. Results show that courgette has the potential to improve bumblebee population dynamics. Nonetheless, bees will only benefit from this transient nectar source if alternative floral resources (particularly pollen) are also available to fulfil their nutritional requirements in space and time. This study is the first to quantify and simulate the importance of courgette as a mass‐flowering forage resource for bumblebees and highlights the importance of matching crop, wild flower, and pollinator species' phenologies to improve bumblebee populations and therefore pollination services. [ABSTRACT FROM AUTHOR]

Trapline foraging (repeated sequential visits to a series of feeding locations) is a taxonomically widespread but poorly understood behavior. Investigating these routing strategies in the field is particularly difficult, as it requires extensive tracking of animal movements to retrace their complete foraging history. In a recent study, we used harmonic radar and motion-triggered video cameras to track bumblebees foraging between artificial lowers in a large open field. We describe how all bees gradually developed a near optimal trapline to link all lowers and have identified a simple learning heuristic capable of replicating this optimization behavior. Our results provide new perspectives to clarify the sequence of decisions made by pollinating insects during trapline foraging, and explore how spatial memory is organized in their small brains. [ABSTRACT FROM AUTHOR]