Bees bumble through their flight plan

Radar tracking of bee flight paths shows that they initially find flowers by trial and error, and refine their route on successive attempts.

Researchers attached tiny transponders to the backs of bumblebees (Bombus terrestris) and set them loose in a field with five artificial flowers, arranged in a pentagon with 50 metre sides. This distance is three times further than bumblebees can see, so they weren’t able to navigate simply by seeing the next target.

Additionally, the amount of sugar available at each ‘flower’ meant that a bee had to visit all five to get its fill. They were each given 7 hours to forage, repeated every day for a month (Lihoreau M, Raine NE, Reynolds AM, Stelzer RJ, Lim KS, Smith AD, Osborne JL & Chittka L 2012, “Radar tracking and motion-sensitive cameras on flowers reveal the development of pollinator multi-destination routes over large spatial scales”, PLoS Biology, doi:10.1371/journal.pbio.1001392).

A bumblebee worker with a transponder attached to its back, visiting an oilseed rape flower
A bumblebee worker with a transponder attached to its back, visiting an oilseed rape flower (Photo by Andrew Martin, via PLoS Biology)

Initially, the flight paths appeared random, but as time went on the bees discarded the longer routes, and so gradually optimised their path. The total distance flown every day dropped dramatically, from 1,953 metres at the start of the month to only 458 metres by the time they finished.

This apparent trial-and-error approach has led the researchers to conclude that the bees learn a route by remembering what direction and how far to fly. This is opposed to previous studies, that have claimed that bees have a sophisticated ‘cognitive map’ of the location of each flower (e.g., Menzel R, Greggers U, Smith A , Berger S, Brandt R, Brunke S, Bundrock G, Hülse S, Plümpe T, Schaupp F, Schüttler E, Stach S, Stindt J, Stollhoff N & Watzl S 2005, “Honey bees navigate according to a map-like spatial memory”, PNAS, vol. 102 no. 8, pp. 3040-3045, doi: 10.1073/pnas.0408550102).

The behaviour observed in the latest study is possible without such detailed spatial data, and so is more in line with the capability you’d expect from bumblebees’ tiny brains.

Even so, it’s remarkable how quickly this new method is able to produce an optimised flight path without a big brain, and all while lugging a hefty radar transponder.

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