Olfactory eavesdropping mediates stingless bee foraging patterns

Stingless bees deposit target-only odor marks and odor trails that help nestmates locate high-reward floral resources. Because such marks exist in the public domain, they are susceptible to eavesdropping by competitors. Dominant species, which displace other species from food sources, should benefit by eavesdropping on odor trails of subordinate species, because dominant species can be relatively poor at locating new food sources (the dominance-discovery trade-off). We show that dominant species can detect odor marks deposited by subordinate species, but that their response to these marks is context-dependent. One dominant species is attracted to odor marks of a subordinate species only when scouting for new food sources, while another appears to switch from attraction to avoidance depending on odor mark concentration. These results suggest dominant stingless bee species follow a cost-minimizing strategy when eavesdropping on odor marks of subordinate species. Subordinate species, however, show variability in the degree to which their eavesdropping behavior appears risky. Some species “play it safe” and avoid odor marks of dominant species, while others seem unaffected by these marks, responding the same as when no odor marks are present, and forage in a manner that may put them at high risk of attack. Our results indicate that how stingless bees respond to heterospecific odor marks is a complex behavior varying with dominance, strength of odor marks and location; complex behavior rules resulting from interactions between these factors are of interest for future research.