Male bumblebees sustain mate-seeking by adjusting foraging to environmental conditions

Abstract Male bees navigate complex trade-offs between energy acquisition and reproductive signaling, yet their movement strategies remain understudied. Unlike workers that optimize foraging to support the colony, male bumblebees (Bombus terrestris) forage independently to collect nectar and deposit sex pheromones on selected plants. Using high-resolution 3D tracking in an indoor flight cage, we investigated how the spatial arrangement of nectar and scent-marking sites, along with nectar availability, influence male movement patterns. We manipulated the distribution of feeders (artificial flowers) and scent-marking locations (branches), and varied nectar delivery rates, to assess effects on foraging, scent-marking, and patrolling. Males responded strongly to spatial structure: in clumped arrays with evenly spaced resources, movements between consecutive visits were shorter and more localized, while in dispersed arrays with irregular spacing, transitions were longer and more variable. The combination of dispersed spacing and low nectar availability imposed the highest foraging demands, resulting in fewer feeding events and reduced total feeding time. Despite these increased costs, males maintained consistent investment in reproductive behaviors, suggesting a prioritization of mate-seeking over energy gain. Rather than reducing signaling, males adjusted their foraging strategy—favoring fewer but prolonged feeding bouts when nectar availability allowed. These findings reveal a unidirectional behavioral adjustment, in which foraging is modulated to sustain reproductive effort, and show how spatial resource structure and nectar availability together shape movement decisions in male pollinators.