Honey Bee Super-Foragers can be Replaced by Hive Mates if Necessary
Many social insect species have a small proportion of individual workers that perform a disproportionately large fraction of the work achieved by the colony as a whole. For example, a honey bee colony might contain a group of elite workers who forage much more than their hive mates.
In order to observe this phenomenon, scientists from the University of Illinois at Urbana-Champaign attached radio-frequency identification (RFID) tags to hundreds of individual honey bees and tracked them for several weeks. The effort yielded two discoveries: 1) Some foraging bees are much busier than others, and 2) if the busy bees disappear, others will take their place.
The findings are reported in the journal Animal Behaviour.
“We found that some bees are working very, very hard — as we would have expected,” said Dr. Gene E. Robinson, who led the research. “But then we found some other bees that were not working as hard as the others.”
Tagging the bees revealed that about 20 percent of the foraging bees in a hive brought home more than half of the nectar and pollen gathered to feed the entire hive.
The technique for attaching RFID tags to the bees and tracking their flight activity with monitors was developed by citizen scientist Paul Tenczar. He and graduate student Claudia Lutz measured the foraging activities of bees in several locations, including some in hives in a controlled foraging environment.
“Previous studies, primarily in ants, have found that some social insects work much harder than others in the same colony,” Robinson said. “The assumption has always been that these ‘elite’ individuals are in some way intrinsically better, that they were born that way.”
However, when the researchers removed the elite bees, they noticed “an almost five-fold increase in activity level in previously low-activity foragers.” The less productive bees stepped up and became better foragers after the all-star team had been taken away, and the change occurred within 24 hours.
While it is well known that genetic differences underlie differences in many types of behavior, the new findings show that “sometimes it is important to give individuals a chance in a different situation to truly find out how different they are from each other,” according to Robinson.
“This demonstrates that other individuals within the hive also have the capacity to become elites when necessary,” Robinson said. “It is still possible that there truly are elite bees that have some differential abilities to work harder than others, but it’s a larger group than first estimated. Or it could be that all bees are capable of working at this level and there’s some kind of colony-level regulation that has some of them working really, really hard, making many trips while others make fewer trips. Perhaps the less-busy bees function as a kind of reserve force that can kick into high gear if something happens to the super-foragers. Our observation is that the colony bounces back to a situation where some bees are very active and some are less active. Why is that? We don’t know. Do all bees have that capability? We still don’t know.”
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