Brackish Sodium salt attractive, Potassium salt aversive to bee foragers
The perennial questions about bees nuisance foraging at swimming pools and spas is answered by this new bit of research. The study also shows a potential prevention strategy-- using potassium salt to train bees off a water source.
J Exp Biol. 2016 Jan 28. pii: jeb.132019. [Epub ahead of print] Salt preferences of honey bee water foragers.
Lau PW1, Nieh JC2.
The importance of dietary salt may explain why bees are often observed collecting brackish water, a habit that may expose them to harmful xenobiotics. However, the individual salt preferences of water-collecting bees were not known. We measured the proboscis extension reflex (PER) response of Apis mellifera water foragers to 0-10% w/w solutions of Na, Mg, and K, which provide essential nutrients,. We also tested phosphate, which can deter foraging. Bees exhibited strong preferences: the most PER responses for 1.5-3% Na and 1.5% Mg. However, K and phosphate were largely aversive and elicited PER responses only for the lowest concentrations, suggesting a way to deter bees from visiting contaminated water. We then analyzed the salt content of water sources that bees collected in urban and semi-urban environments. Bees collected water with a wide range of salt concentrations, but most collected water sources had relatively low salt concentrations, with the exception of seawater and swimming pools, which had >0.6% Na. The high levels of PER responsiveness elicited by 1.5-3% Na may explain why bees are willing to collect such salty water. Interestingly, bees exhibited significant high individual variation in salt preferences: individual identity accounted for 32% of PER responses. Salt specialization may therefore occur in water foragers.