Australian stingless bees detect odours left at food sources by nestmates, conspecifics and honey bees

Many animals deposit odours in their environment, either intentionally or unintentionally, that remain at a site after the animal itself has left. These odours may be exploited by other species as social information, and thus have a significant role in structuring species interactions, even where the species involved rarely interact directly. Here we show that three species of Australian social stingless bees (Meliponini) not only detect the odours left behind by conspecifics, but also those of an abundant introduced competitor, the honey bee Apis mellifera (Apini). Foraging bees deposit pheromones that assist nestmates in locating profitable food sources (signals) and/or involuntary olfactory "footprints" (cues), both of which are vulnerable to exploitation by the foragers of other colonies. Using choice trials, we find that foragers of Tetragonula carbonaria, Tetragonula clypearis and Austroplebeia australis were more attracted to feeders recently used by, and thus carrying the odours of, their own species (both nestmates and non-nestmates) or honey bees, than to clean unused feeders. Australia's stingless bees may learn to associate honey bee odours with food and exploit this to their advantage, or they may mistake honey bee odours for some other attractant and be misdirected. Our results suggest that introduced social insects could have a previously overlooked impact on resident communities, by modifying the olfactory landscape of shared resources in ways that alter native species' foraging behaviour.